Index to specific names

Twenty-six species were described between 1817 and 1935 under the different names given to the genus: none of them under Xyleus. No synonymies have been formally made before the present paper, though there is an indication by Liebermann (1942: 25) that his species Diedronotus uvarovi might be the same as Tropinotus insignis Giglio-Tos, and a comment by Descamps (1975: 52) to the effect that specimens that had been identified as Diedronotus mexicanus Bruner and D. centralis Rehn seemed identical to him. According to the present work, the genus includes 16 valid species (one of them with 3 subspecies), of which 5 (and 1 subspecies) are here described. Eleven nominal species are synonymized in this paper, and one is eliminated as nomen dubium et oblitum.

In the list that follows, specific (or subspecific) names are in alphabetical order. Another order judged to be more related to the taxonomy of the group is followed in the text. Numbers given after each of the names correspond to those given to the species in the text. Names set in boldface are valid, all other names correspond to junior synonyms or are invalid for other reasons. Generic names in parenthesis are those under which the corresponding species were described.

The following species have been in the past assigned to Tropinotus but are now not placed in Xyleus:

Genus XYLEUS Gistel 1848

Several authors have given their opinions about the proper name for this genus. Caudell (1932) mentions that the name Tropinotus Kuhl 1822 (Reptilia) antecedes Tropinotus Serville 1831, but that on the opinion of Dr. Leonhard Stejneger, Kuhl's name would be a nomen nudum. Tropidonotus Stål (1878a, b), proposed as an emendation of Tropinotus, could not be used because Tropidonotus Boie 1826 (Reptilia) was a valid name. He concluded that the name Xyleus Gistel 1848, proposed to replace Tropinotus Serville, should be used, while Tropidonotus Stål 1878138 and Diedronotus Bolivar 1906 should be considered junior synonyms of Xyleus. Uvarov (1940) discussed the case again, arriving at the same conclusion. Roberts (1937) refers to the above opinion of Caudell, pointing to the fact that if Tropinotus Kuhl was a nomen nudum as indicated by Caudell, Tropinotus Serville would be valid and should be used for this genus.

The validity of Xyleus Gistel as the proper name for this genus would hence depend on the status of Tropinotus Kuhl (Kuhl & Hasselt, Isis 1822: 474; Kuhl 1824: 81). I have consulted Dr. M.S. Hoogmoed and Dr. T.C. Avila-Pires of the Department of Herpetology of the Nationaal Natuurhistorisch Museum in Leiden on the subject of the status of Tropinotus Kuhl 1822. After a study of the pertinent literature and discussion with other members of the staff, they informed me that Tropinotus Kuhl 1822 is an available name on the terms of article 11.(c),(i) of the International Code of Zoological nomenclature. It was not associated to any specific name (not necessary for names published before 1931), but in both papers mentioned above (1822, 1824) there are brief descriptions of the genus. Tropidonotus Boie (Isis 1826: 982, 1827: 474) described and associated with a specific name in Reptilia, is without doubt an available name. Hence, the name Xyleus Gistel 1848 is the proper name for the present romaleid genus.

I have not found any further discussion on the status of Xyleus after the above mentioned papers of Roberts 1937 and Uvarov 1940, but this generic name has been generally adopted in subsequent literature.

Etymology.—According to Brown (1956: 864, 870) the word xyleus (from the Greek, xylon = wood) means wood-cutter. Most species of the genus, by their color and color-pattern, look like chips of wood, and this is probably the origin of this name as applied to them.

Distribution.— (Figs 36, 46). According to the specimens available for this work, the genus has a discontinuous geographical distribution. It is found in southern South America, east of the Andes between parallels 5° and 35° S and meridians 34° 55′ and 76° 50′ W (the only exception being X. camposi). In northern South America and Central America it occurs between parallels 4° and 21° N and meridians 61° 13′ and 104° W. I have seen no specimens from any part of the continent between 5° S and 4° N, which includes the main course of the Amazon River and part of the Guianas. Many localities in the Brasilian part of this zone have been well collected by Dr. Campos-Seabra's collectors, some in French Guiana by Marius Descamps, and several in the Peruvian part by Amedegnato and Poulain, but no specimens of this genus have been found. An exception is the species X. camposi coming from Posorja, Ecuador, west of the Andes, at 2° 35′ S. Another is a single specimen of X. goias (labeled as from Amapa State) which I suspect of being mislabeled.

Another interesting fact regarding this geographical distribution, is that all specimens collected in the northern area belong to subspecies of Xyleus discoideus, which is the species found along the Atlantic coast in southern South America. It seems probable that this species migrated along the coast from Northeastern Brasil to Venezuela, Colombia and Central America. However, the mouth of the Amazon River, one of the rainiest areas of the Amazonian main course, seems at present an uncrossable barrier for the species; though of course, conditions there have certainly changed through the ages. Also, Xyleus discoideus like other species of the genus, is a weak flier, and its flying across any part of the Amazon River, such as it is now, is unthinkable. The antiquity of the South American romaleines is not known with any certainty, but they are probably among the oldest groups of autochtonous neotropical acridoids. Amedegnato (1993:69) states that they “may be the most primitive of true acridians”. It has been postulated (but not proved), that the Amazonian basin was open to the Pacific before the lower Miocene. If so, the passage of X. discoideus along the Atlantic coast might have taken place by dry land, at the time when the Amazonian basin was open to the Pacific and before the rising of the corresponding part of the Andes. But as far as I know, the passage of X. discoideus to the north along the Atlantic coast or by any other route, is at present a matter of speculation.

The center of origin of this genus is indeed the region in south-central South America that includes the Brasilian states of Goias, Mato Grosso, Sao Paulo and Minas Gerais and also northern Argentina, Paraguay, Bolivia and parts of Peru east of the Andes. In this region all the species of the genus are found.

Habitat.—According to some records in the bibliography, and my own observations in the field, most species of Xyleus inhabit dry forests and savanna, and in general, places with scattered trees or bushes, or the edges and more open parts of forests (Astacio-Cabrera 1975; Bucher 1974; Descamps 1975, 1976; Rowell 1987). The only species that is always found in the prairie habitat seems to be Xyleus laevipes (Bruner 1900, my own records).

Food-plants, economic importance.—Gangwere & Ronderos (1975) describe the mandibles of several species of Xyleus as of the forbivorous type, and indicate that the analysis of feces reveals that they are unselectively polyphagous in their food habits. In many publications attacks on diverse crops, particularly sugarcane and tobacco, are recorded, but the damage observed is said to be unimportant. In general, species of this genus have not been reported as of much economic importance.

Cytology.—Most records on the chromosomes of the species of Xyleus are summarized in Mesa et al. 1983. Of the 9 species there recorded (attenuatus, discoideus, gracilis, insignis, laevipes, modestus and 3 unidentified species) 8 have a chromosomic formula 23 (2n, m)–24 (2n, f) X0 (m) XX (f). The only one with a different formula is X. laevipes, with 22-22-XY-XX.

Taxonomy.—Type-species: Tropinotus discoideus Serville. This is the only species associated with this genus in its original description that has not been posteriorly removed from it. Its status as its type-species is indicated by Rehn (1907: 170) and Kirby (1910: 359).

The romaleine genera most closely related seem to be Prionolpha Stål, Colpolopha Stål (Figs 1, 2) and Securigera Bolivar. Differences between the first two genera are summarized in Table 1 (see also Fig. 1). Securigera has no significant differences with Prionolopha, and these names are probably synonyms. Differences with other romaleines that have a crested pronotum, such as Alcamenes, Taenipoda, Titanacris, Tropidacris and others are great, and become evident just by comparing specimens of them with the habitus figures in this work.

Rowell & Flook's (1998) study of ribosomal DNA sequences in acridoids only reveals the affinities of Xyleus with other romaleines they studied (Zoniopoda, Phaeoparia, Abila), and with some genera of ommexechids. The genera indicated above as related to Xyleus were not included in their study.

Characters of genus.—Grasshoppers in this genus are medium-sized. Among 219 specimens measured in this study, the largest and smallest are the following (from frons to end of tegmina, or to end of abdomen in the case of X. camposi):

Males: largest ones— 49 mm (rosulentus), 45 mm (mexicanus), 44 mm (discoideus). smallest ones— 31 mm (guarani), 32 mm (modestus, regularis).

Females: largest ones, 70 mm (rosulentus), 63 mm (discoideus), 62 mm (mexicanus). smallest ones— 37 mm (camposi), 40 mm (guarani, modestus, regularis).

Head: antennae flattened, from slightly to moderately ensiform; eyes large, elyptical, moderately prominent, more so in males than females; vertex prolonged before eyes in a triangular fastigium, somewhat excavated dorsally; dorsal median carinula running from fastigium to occiput. Pronotum: dorsal carina elevated, crest-like, cut by 3 transverse sulci; lateral carinae prominent, diverging caudad; lateral lobes vertical, in definite angle with disk; prosternal tubercle compressed or swollen, always retrorse. Meso- and metasternal spaces subquadrate. Tegmina and wings well developed in all known species excepting X. camposi which is brevialate. Tegmina (Fig. 4) rather narrow, with marked precostal lobe and variously shaped apices. Wings (Fig. 4) wide, stridulatory area well developed in both sexes. The remigium rather narrow, usually colored in shades of brown, fuscous or umber, like the tegmina. Vannum is the wings' most characteristic part. What are apparently veins A1 and A2 are placed close together, and between them runs a series of strong, denticulated arched veinlets acting as scrapers during stridulation. Behind them, between A2 and A3, which are widely separated, there is a hyaline area with marked crossveins, likely a radiating area during stridulation. The whole margin of the vannal area is marked by a dusky band of the same color as the remigium, which is rather wide at its limit with the remigium but gradually narrows backwards. The rest of the vannum, between this dusky band and the hyaline resonatory area, is colored in variable shadows of scarlet to orange. This color may be different in different species, and is also somewhat variable within each species. The stridulating apparatus as described above is common to most romaleines. Legs not particularly strong except hind ones: hind femora with well marked carinae, the median dorsal one more or less markedly serrulate, the upper external and medial ventral ones frequently so. Brunner´s organ present. Hind tibiae armed with rather large spines, apical external one present in all known species. Abdomen with auditive organ on 1st segment. Male abdominal terminalia with dorsum of 10th segment deeply incised medially, epiproct rhomboidal, cerci straight, subconical, subgenital plate apically pointed. Male genitalia species-specific; form of cingulum and apical endophallic valves particularly useful as species characters. Female with ovipositor of the soil-laying type.

Characters used for the description of species

From a study of the pertinent literature, it has been found that the following characters have been used in most cases, to define the different species.

Colors and color-pattern.—These are not usable without an under-standing of how they vary within each species. Some species have fairly uniform colors and color pattern (e.g., X. laevipes) while in others both are highly variable. In X. insignis for example, specimens vary from a uniformly green coloration to the most diverse patterns of buff, brown and fuscous. In some of the species-groups defined below, the same color-patterns may appear in individuals of different species. As used in most existing descriptions, these color characters are entirely unreliable.

Shape of fastigium.—This is somewhat variable intraspecifically. Slight differences in form have no meaning for the definition of species.

Pronotum.—Measurements made in this work show that the height of the pronotal crest is fairly variable within the same species. However, some species have a high, arcuate crest, while in others it is lower and almost straight. Such marked differences are definitely useful. Crenulation of pronotal crest is variable. In specimens of X. d. discoideus for example, these crenulations diminish in a geographic gradient from north to south. Some of the southernmost specimens may lack them altogether. Some species, however, may always have a crenulated crest, while in others the crest is always smooth throughout.

Transverse sulci of pronotum: in some species these sulci are well marked, deep in some places, and the 4 lobes into which they divide the pronotal crest may be not entirely contiguous superiorly. In other species these sulci are less marked, and the different lobes always contiguous.

Shape of the pronotum as seen from above is a valuable character, but the same shape can be seen in different species, for example in X. discoideus angulatus, X. modestus and X. discoideus venezuelae. This shape is, however, clearly distinguishable from the one seen in X. d. discoideus, X. andinus and X. discoideus rosulentus (Figs 5, 14, 21).

Prosternal tubercle.—While fairly variable intraspecifically, each species has a characteristic pattern. Examining series of each species is useful for determining the extent of these variations. This may be a useful character when used in combination with others.

Spines on hind tibiae.—Tibial spines vary in different species from 9 to 19. The number is slightly variable within each species, but in general can be taken as an auxiliary character. For example, this number varies from 9 to 11 in several species, from 15 to 16 in others, but no overlapping will occur in such a case. Tibial spines are rather large, the internal ones larger than the external.

Tegmina.—(Fig. 4). Size of tegmina is somewhat variable within each species. The only brevialate species known is the Ecuadorian Xyleus camposi. The most reliable tegminal character seems to be the shape of their apices, though even this is subject to some intraspecific variation. Also in some species chromatic characters of the tegmina are of value, such as the presence and location of dark areas or markings. The color of these varies usually in shades of brown, fuscous or umber, but in some species some parts are green, particularly on the costal and anal areas.

Wings.—(Fig. 4). Their color pattern is characteristic for the genus. Remigium and the edge of vannum are usually colored in shades of fuscous or umber; a large basal area of the vannum is colored in shades of scarlet or orange. There is in both sexes a well differentiated stridulatory area in the vannum, which is common to most romaleines. While colors and details of color pattern may be slightly different in different species, these differences are not marked and do not seem useful for purposes of species identification.

Phallic complex.—Not generally used before the present paper to define the different species, it has proved to possess the most reliable characters (in some cases apparently the only ones) for the separation of the species. Shape of the cingulum and of the apical endophallic valves, is particularly useful.

Geographical range.—While some species are totally or partially sympatric, others are entirely allopatric, their ranges being clearly separated. For example, such is the case with 3 species which are externally similar: X. modestus from Central Brasil-Paraguay-Eastern Bolivia-Central Argentina; X. discoideus angulatus from NE Brasil, and X. discoideus venezuelae from Venezuela.

Discoideus Species Group (Figs 5, 6, 13)

It includes what are here considered to be the most primitive species. This should be construed in the sense of the species having a phallic complex which does not greatly diverge from that found in most romaleines. In their external morphology and color pattern all its members are fairly similar. Included in this group are the 5 subspecies of Xyleus discoideus, namely discoideus, angulatus, mexicanus, rosulentus, and venezuelae. As said above, Xyleus camposi, whose male is unknown, may belong in this group.

Being composed of 5 subspecies of a single species, this group is in every sense very uniform. Its species are dull-colored in various shades and hues of umber, fuscous and brown, and some of them russet or hazel. Some specimens of any of the subspecies may have some dull-green coloration in the upper parts of the body and tegmina, but this condition is uncommon. Within each of the species, the color-pattern of the different individuals is very variable; no 2 individuals are exactly alike. For the present study I have examined more than 300 specimens of this species-group, without finding a single individual with colors other than those indicated above. The differences that allow the separation of the various subspecies lie mainly in the shape of the pronotum as seen from above, and in the phallic complex, especially the apical endophallic valves and the cingulum. Also the size varies somewhat in the different subspecies (see tables of measurements), specimens of X. d. angulatus, for example, being in general of a smaller size than those of the other subspecies.

The species X. discoideus as a whole can be characterized as follows (differences among subspecies will be given below when referring to each of them). Pronotal crest high, especially on metazona. Transverse sulci of pronotum very well marked and deep: in side view some of the lobes into which they divide the pronotal crest are not entirely contiguous and show narrow gaps between them. The posterior part of the crest at least is usually crenulated (though this character is subject to some intra-subspecific variation). Hind femora very strong, with their median dorsal and ventral carinae strongly serrulated.

Xyleus discoideus (Serville 1831)

Taxonomy.—This species is treated here as polytypical. X. angulatus, X. rosulentus and X. mexicanus, considered in the past as separate species, differ from it, but very slightly, and so does X. venezuelae, here described. All these are treated here as subspecies of X. discoideus.

Distribution.—(Figs 37, 38, 39, 40, 41, 46). Considering this species as a whole, it is distributed along the Atlantic coast of South America (X. d. discoideus, X. d. angulatus) and also in Venezuela (X. d. venezuelae), Colombia (X. d. rosulentus) and Central America to Southeast Mexico (X. d. rosulentus, X. d. mexicanus). It seems probable that X. d. venezuelae extends into parts of Guyana (formerly British Guiana). South of the Amazon, the species occupies mainly the Atlantic coast, though in some places it reaches far inland.

1. Xyleus discoideus discoideus (Serville 1831) (Figs 3, 4, 5, 6, 7, 13, 37, 46, Table 3)

Taxonomy.—Tropinotus discoideus was briefly described by Serville (1831: 273), and redescribed later (1839: 619) in a somewhat more extended form. Both descriptions are inadequate in the light of present knowledge. Most characters given in them are common to most subspecies of what is here referred to as the Discoideus Species Group, and some even to the whole genus Xyleus. In his first description Serville refers to male and female specimens. In the second one only a female is mentioned.

The species Tropinotus discoideus, being that first described in what is now the genus Xyleus, must be considered as the type-species of this genus and is indicated as such by Rehn (1907: 170, genus Tropinotus) and later by Kirby (1910: 360, genus Diedronotus). Its type specimen, believed to be lost, was recently found in PARIS by Dr. Amedegnato, who has kindly compared it with specimens from the State of Rio de Janeiro and found it to be conspecific with them. Being the type-species of the genus, it seems very important to know to which species this name should be applied. Another reason for trying to identify this species, is the fact that it has been the most frequently mentioned in the literature among those of its genus. Many of these mentions will probably be due to misidentifications.

Its type locality, given by Serville as “Brésil”, is not very helpful for this purpose. It seems, however, that for a specimen collected before 1831, some place in coastal Brasil is more probable than one inland. Also, Serville's indication of his type-specimen having denticulations on the posterior part of its pronotal crest, points to a specimen from the northern part of the known range of the species (see below). Rio de Janeiro, being an accessible place at that time, seems very probable as the type-locality.

It is curious to notice that such an ill-defined species was taken in subsequent literature as the main reference for defining other members of the genus, which are compared with it in their descriptions. Out of 23 descriptions of other species, 12 refer to discoideus for comparison, pointing to similarities or differences with it to characterize the species under description. Also, the authors who refer to this species assign to it a very large geographical range that includes Colombia, British Guiana, different places in east Brasil, such as Bahia, Rio de Janeiro and Porto Alegre, Uruguay, all of the provinces of Argentina from Misiones and Jujuy in the North to Buenos Aires in the South, and also southeast Bolivia and eastern Paraguay. In the light of the present revision, this suggests that all the taxa we consider in this work to be subspecies of X. discoideus and very probably other species as well, have been in the past identified as X. discoideus.

Distribution.—(Fig. 37). According to the localities of collection of the specimens examined (see Appendix I) this species ranges along the Atlantic coast from southern Bahia State in Brasil to Uruguay and probably also the extreme north of the Province of Buenos Aires in Argentina. It extends inland to the west as far as Goias and Minas Gerais in Brasil, eastern Paraguay, southeastern Bolivia and the Argentinian provinces of Formosa and Chaco (eastern parts), Misiones, Corrientes and Entre Rios. This subspecies thus reaches to the west as far as the 60° meridian, more than 2000 km inland from its easternmost record on the Atlantic coast.

Habitat.—I have observed this species in nature in Uruguay and in many localities in Brasil. It lives in places with trees, and prefers plant formations with rather scattered trees, in the case of woods, their edge or clearings. Is one of the few species that has managed to survive in parks and large gardens in cities and towns. I have never found it in prairie or open fields. The type of habitat described for this subspecies seems similar to that of other species I have collected, such as X. modestus and X. insignis.

Identification.—Figures 3 - 7 and 13, together with what has been said on the coloration of the species group, will be enough for the identification of the species. It must be noticed (Fig. 5) that the pronotum as seen from above has the lateral angles of the metazona always rounded, never sharply angulated as in angulatus or venezuelae. Also its geographical distribution as stated above is important for its identification, other species sympatric with it can hardly be mistaken for the present subspecies of X. discoideus. The pattern of the dark markings on the tegmina is characteristic of X. discoideus in general, and shared with the other subspecies. Number of spines in hind tibiae: 10 to 11, rarely 9.

2. Xyleus discoideus angulatus (Stål 1873135) new status (Figs 5, 8, 9, 13, Table 4)

Taxonomy.—In much of the literature, this species has been mistaken for X. modestus and less frequently for other species. Whenever it is mentioned for regions different from northeast Brasil, it is certainly due to misidentifications.

Distribution.—(Fig. 38). Northeastern Brasil, including the states of Rio Grande do Norte, Ceara (southern part), Paraiba, Pernambuco, Alagoas (probably Sergipe) and Bahia. It is there a very common and abundant species. From an ecological point of view, it is worthy of notice that it is found in very different biogeographical provinces, including parts of Caatinga, Cerrado and Atlantica of Cabrera & Willink (1973). Its limit with X. d. discoideus lies around parallel 16° S in southern Bahia, near the coast, coinciding approximately with the course of the Rio Jequitinhonha.

Identification.—Figures 5, 6, 8, 9 and 13 depict the most important features for the identification of this subspecies. The shape of the pronotum as seen from above, with the sharply angulated sides of the metazona, is characteristic. The shape of the cingulum (Fig. 13) and of the apical endophallic valves (Fig. 6) is also important for identification. Number of spines on hind tibiae: 9 to 10.

3. Xyleus discoideus venezuelae n. ssp. (Figs 5, 6, 10, 13, 39, 46, Table 5)

Taxonomy.—The only bibliographical reference to this species is probably the one by Guagliumi (1962: 449) that lists it as Tropinotus angulatus (attacking sugarcane) in Venezuela. Among the subspecies of X. discoideus, it seems near to X. d. angulatus, but the characters mentioned below mark the difference.

Distribution.—(Figs 39, 46). Specimens examined come from a large part of Venezuela north of parallel 7° and west of meridian 63°.

Identification.—The characters for the identification of this subspecies are in Figs 5, 6, 10, and 13. Its prothorax as seen from above (Fig. 5) has the metazona angulate laterally, like X. d. angulatus. In its phallic complex, the cingulum (Fig. 13) and apical endophallic valves (Fig. 6) have characteristic shapes that allow its identification. Number of spines on hind tibiae: 10 to 11.

4. Xyleus discoideus rosulentus (Stål 1878138) new status (Figs 5, 6, 11, 13, 40, 46, Table 6)

Taxonomy.—Described by Stål as a separate species, but in the light of the present revision it seems more adequate to consider it a subspecies of X. discoideus.

Distribution.—(Figs 40, 46). Easternmost Costa Rica, Panamá and Colombia as far east as meridian 73° W. Its limit with X. discoideus venezuelae described below, cannot be ascertained from the materal now at hand, but seems to lie somewhere near the border of Colombia and Venezuela. In Colombia it reaches south as far as parallel 4° N.

Identification.—(Fig. 11). Its pronotum as seen from above shows the lateral angles of the metazona completely rounded (Fig. 5), without any traces of the angulation found in other subspecies. Characters of its cingulum (Fig. 13) and apical endophallic valves (Fig. 6) allow its easy identification. Spines on hind tibiae: 10 to 11.

5. Xyleus discoideus mexicanus (Bruner 1906) new status (Figs 5, 6, 12, 13, 41, 46, Table 7)

Taxonomy.—As in the case of X. rosulentus, it was described (by L. Bruner) as a separate species. I think it more adequate to treat this as a subspecies of X. discoideus, its differences with its typical subspecies being slight.

Distribution.—(Figs 41, 46). Southeast Mexico, Central America to and including parts of Costa Rica. It is replaced east and south by X. d. rosulentus.

Identification.—(Fig. 12). In dorsal view, its pronotum (Fig. 5) shows lateral angles almost rounded, but marked with small lateral points. Best characters for identification are in the phallic complex, especially in the cingulum (Fig. 13) and apical endophallic valves (Fig. 6). Number of spines on hind tibiae: 10 to 13.

Laevipes Species Group

By the structure of its phallic complex, the Laevipes group seems closely related to the Discoideus and includes X. laevipes, X. modestus, X. andinus, X. goias and X. regularis. It is rather heterogeneous, and is made mainly with the purpose of helping in the identification of the species of the genus. Apical endophallic valves (Fig. 15) are of the same general type as in the Discoideus group: short, massive and transversally grooved. Those of X. regularis are the most divergent within the group. The cingulum in all species is fairly similar (Fig. 13) and of the same general structure as in the Discoideus Group. In their external characters, the species in this group are more divergent. X. modestus and X. andinus have their pronotal crest higher, crenulated on its posterior part, with more marked transverse sulci. Also the color-pattern of their tegmina, with a series of dark markings of which the proximal one reaches the costal area, is very similar to the one found in species of the Discoideus Group. X. laevipes, X. regularis and X. goias have their pronotal crest smooth, without any crenulations or denticulations. This crest is relatively high in X. laevipes, lower in X. regularis and X. goias. Colors and color-patterns in the last 3 species are very different (see below).

6. Xyleus laevipes (Stål 1878138) (Figs 13, 14, 15, 16, 42, 46, Table 8)

Taxonomy.—This species has a very characteristic aspect and coloration, that makes it the easiest one within the genus to identify accurately. Its color is always predominantly lime-green; I have seen no specimens of the brown, chestnut or russet colors prevalent in other species. Its prairie and grassland habitat is also very characteristic. Old specimens in collections are sometimes of a buff-yellow color, but this is due to discoloration of the original lime-green color: green colors frequently do not keep well in collection specimens. Also characteristic of this species is a series of (usually 8) subquadrate fuscous spots along the M and Rs areas of the tegmen. These spots are sharply defined, and do not extend into the costal and precostal areas, nor into the cubital area. As said with reference to the genus, this species' chromosomic formula (22-22-XY-XX), is different from that of the other 8 species studied (Mesa et al. 1983).

Distribution.—(Figs 42, 46). Common in southern Brasil (State of Sao Paulo and south), eastern Paraguay, northern and central Argentina south to La Plata, and the whole of Uruguay.

Habitat.—Bruner (1900: 56) says this species lives in open grassland (other species of the genus Xyleus are usually found among shrubs or in wooded areas). I have collected it often, always in open fields with vegetation prevalently of grasses. In Uruguay it is abundant in the northwest, becoming scarcer to the south and east.

Identification.— (Fig. 16). Colors and color-pattern as described above make this species easily identifiable. Its phallic complex also has some characters peculiar to this species. While the apical endophallic valves (Fig. 15) are of the same general type as those in X. modestus and X. andinus, its cingulum (Fig. 13) in dorsal view is different from others in the genus in having the median V-shaped posterior incision reduced to a shallow undulation (compare Fig. 13b with most others in the plate). Number of spines on hind tibiae: 12 to 16.

7. Xyleus modestus (Giglio-Tos 1894) (Figs 14, 15, 17, 44, 46, Table 9)

Taxonomy.— This is probably the species of Xyleus that has been most frequently misidentified. Giglio-Tos (1894: 16) when describing it, states it is very similar to X. angulatus, and lists a series of differences with this species (which he had never seen). His type of X. modestus was a badly shriveled and discolored specimen that had been in alcohol. The only specimens in Giglio-Tos' collection identified as Tropidonotus angulatus are those mentioned in Giglio-Tos 1894: 16, from Argentina and Paraguay, which are certainly X. modestus. When listing the differences between modestus and angulatus, he was obviously comparing his damaged type of X. modestus with the fresh specimens of the same species collected by Borelli, that he believed to be X. angulatus. These 2 forms are externally very similar, but their phallic complex is clearly different. X. discoideus angulatus is endemic to northeast Brasil, while X. modestus inhabits a large territory including parts of Brasil, Argentina, Paraguay and Bolivia. Both ranges are widely separated by a large area where neither species has been found.

Bruner (1900: 56) described specimens of this species as Tropidonotus schulzi, a name frequently used for it in subsequent literature. But he also identified as T. angulatus many specimens collected in the same area. Examination of the voucher specimens show that he came to use this name (angulatus) for most specimens of X. modestus collected in the area. In fact, the name X. modestus has been less used for this species than either X. schulzi or X. angulatus.

Distribution.—(Figs 44, 46). This species is common throughout a large territory in inland South America, that includes at least the states of Rondonia, Mato Grosso and Mato Grosso do Sul in Brasil, most of Paraguay, the lowlands of Eastern Bolivia and northern Argentina south to Cordoba and Corrientes.

Identification.—(Fig. 17). X. modestus has colors and color patterning similar to that of X. discoideus. It is sympatric with X. discoideus discoideus in most of its territory, except in the Atlantic coast where X. modestus has not been found. Most specimens of X. d. discoideus have their pronotum as seen from above, with the sides of the metazona rather rounded, while in X. modestus (Fig. 14b) they are angulate, as in X. d. angulatus, a species with which X. d. discoideus appears not to be sympatric in any part of its territory. Dissection of the phallic complex will clear any doubts, the apical endophallic valves in the 2 species in question being completely different (compare Fig. 15b and Fig. 6b). Number of spines on hind tibiae: 10 to 11.

8. Xyleus andinus n. sp. (Figs 13, 14, 15, 18, 43, 46, Table 10)

Taxonomy.— This is another species with colors and color-pattern not distinguishable from those of X. discoideus. All specimens examined have a pronotal crest that is high and crenulated in its metazonal part, but this is not uncommon in X. discoideus.

Distribution.— (Figs 43, 46). Collection localities of the specimens examined all lie within the eastern slope of the Andes, from parallel 6° in Perú (east of the town of Tarapoto) to parallel 18° in Bolivia (Santa Cruz de la Sierra).

Identification.—(Fig. 18). Individuals of this species are very similar in shape, colors and color-pattern to specimens of X. d. angulatus. However, they inhabit a territory which is entirely separated from that of X. d. angulatus. Together with the locality of collection, examination of their phallic complex may be necessary for an accurate identification: shape of the cingulum (Fig. 13) and of the apical endophallic valves (Fig. 15) being the most important characters. There are 10 to 11 spines on the hind tibiae.

9. Xyleus goias n. sp. (Figs 13, 14, 15, 19, 45, Table 11)

Taxonomy.— In its general aspect, colors and color-pattern, this species contrasts with species of the Discoideus group. In this sense it is similar to X. lineatus and X. pirapora which, by their phallic complex, each belong in quite different species-groups.

Distribution.—(Fig. 45). Known specimens are from south-central Brasil, in the states of Goias and Mato Grosso, except for one labeled Rio Anicohe, Amapá State. This locality seems incongruous even for the distribution of the whole genus, being in an area where no species of Xyleus have been found. It might be due to mislabeling of the specimen. I have found no river Anicohe either in the Carta do Brasil ao Milhonesimo (Instituto Brasileiro de Geografia e Estatistica, 1960) or in the corresponding gazeteer (Vanzolini & Papavero 1968). It may be a small river, not figured in the maps, or a mistake in the label.

Identification.— (Fig. 19). Differing from the species referred to above, which (with the exception of X laevipes) are predominantly of the colors brown, fuscous and umber, X. goias is, in its colors and color-pattern, similar to X. lineatus and X. pirapora treated below. Individuals of the present species may have a green coloration in the costal or anal areas of the tegmina, sometimes in both. Also, and this is a character shared with X. lineatus and X. pirapora, it has a light-colored (yellowish or dirty white) longitudinal band in the costal area, just below and along the subcostal vein. This light-colored band occupies in some individuals almost the whole of the costal area, in others it may be limited to part of the costal area just against the costal vein. This band is neatly marked towards the base of the tegmen and usually in the basal half, getting fainter or sometimes disappearing altogether towards the apical part of the tegmen. Individuals of this species also have a series of subquadrate dark markings or spots along the medial and Rs areas, similar to those described for X. laevipes. These spots may be clearly visible in some individuals, but in others the whole of the said areas is very dark-colored and the spots on them barely visible or, in some cases, not at all. As in X. laevipes, these dark spots are limited to the RM and Rs areas, and do not go into the C and Sc areas. Cingulum (Fig. 13) and apical endophallic valves (Fig.15) are helpful for identification. Number of spines on hind tibiae: 10 to 11.

10. Xyleus regularis (Bruner 1905). (Figs 13, 14, 15, 20, 45, Table 12)

Taxonomy.— Individuals of this species are in general aspect and coloration almost identical with those of X. guarani. The phallic complex in the present species is very different from that of X. guarani, and seems to reveal a closer relationship with modestus, andinus, laevipes and goias than with X. guarani. Within the Laevipes Species Group however, this species' phallic complex is clearly the most divergent from that of the other 4 species in the group.

Distribution.— (Fig. 45). The species is scarce. The limited series at hand indicates it is mostly sympatric with its sibling X. guarani, living in central western Brasil and eastern Paraguay.

Identification.— (Figs 14, 20). By their general aspect and coloration, individuals of this species are hardly distingushable from those of X. guarani. Males can be easily identified by examination of their phallic complex, cingulum (Fig. 13) and apical endophallic valves (Fig. 15), these being characteristic. I have not found a way to identify females with any certainty, and the sympatry of these 2 species makes it impossible to identify them by their association with the males. As in X. laevipes and X. guarani, one of the most prominent color-pattern features is a row of subquadrate dark markings (generally fuscous) on the M-Rs areas of its tegmina. These markings, usually 5 to 6 in males and 8 to 9 in females, are well-defined on the M area, becoming fainter on the Rs area, and gradually disappearing towards the tip of the tegmen. The general color of specimens is tawny to cinnamon, frequently being light shades of these colors. On these background colors, there are usually many small irregular dark markings (fuscous or umber). One female specimen has the anal (dorsal) area of its tegmina of a light olive-gray color; the lateral parts of its pronotal disk are also of this color, while the median part is fuscous. Number of spines on hind tibiae: 9 to 10.

Attenuatus Species Group

Includes 5 species: X. attenuatus, X. araguaia, X. gracilis, X. pirapora and X. laufferi. The first two are very closely related: they might be considered as subspecies, but differences in phallic complex, particularly in the cingulum (Fig. 27) and the apical endophallic valves (Fig. 22) seem to justify specific status. X. gracilis is, in its external characters, close to the above two, but its phallic complex is clearly different. X. pirapora is the most divergent, and its inclusion in this group may be based only on some similarities unrelated to phylogeny. X. laufferi, known by its unique female type, might be identical with X. attenuatus, X. gracilis or X. araguaia, but in the absence of a male, its true status cannot be ascertained at present.

Species of this group share some external characters. The pronotal crest is low, (particularly in the metazona) and smooth, generally devoid of any denticulations or crenulations, except in X. araguaia and in some specimens of X. attenuatus: here the metazonal part of the crest may have some low and inconspicuous crenulations. Transverse sulci of the pronotum are shallow, sometimes not very marked; hence the pronotal lobes are entirely contiguous. Hind femora are narrow in proportion to their length: their median dorsal and median ventral carinae have only very small and low denticulations; denticulations may be absent in some male specimens of X. gracilis.

Chromatic characters: specimens are predominantly brown (shades of brown, fuscous or umber) in all species. In some specimens in all species the costal area of tegmina may be green, but in most it is of as many different shades and hues of brown as the rest of the tegmen. The area of the tegmen just above R and M may present a series of dark (fuscous) spots (as shown in the habitus figures of X. attenuatus and X. araguaia) that never enter the costal area.

11. Xyleus attenuatus (Rehn 1909) (Figs 21, 22, 23, 27, 45, Table 13)

Taxonomy.— Most external characters are mentioned above in relation to the species-group. In all specimens of both sexes the lateral lobes of the pronotum show a series of roughly parallel longitudinal dark stripes, but this character is shared with X. gracilis, and can be seen also in the only female specimen of X. araguaia examined. With reference to the nomenclature of this species, see observations under X. laufferi.

Distribution.—(Fig. 45). This is an inland species, known from northern Bolivia and central-western Brasil (Rondonia, Mato Grosso, Goias, Minas Gerais), reaching near the Atlantic coast in Sergipe. The species is not abundant, and its distribution is probably more extensive than is here registered, as suggested by the Sergipe specimens.

Identification.— (Figs 21, 23). The phallic complex offers the best specific features, especially in the apical endophallic valves (Fig. 22) and the shape of the cingulum (Fig. 27). Number of spines on hind tibiae: 12 to 14.

12. Xyleus araguaia n. sp. (Figs 21, 22, 24, 27, 44, Table 14)

Taxonomy.— In its external features it is almost identical with X. attenuatus. The 3 known specimens are paler in color than most specimens of X. attenuatus.

Distribution.— (Fig. 44). Apparently an uncommon species, it is known only by the typeseries from the southeast of the State of Mato Grosso. This locality is 350 km southeast of Chapada dos Guimaraes and only 75 km northwest of Mineiros (Goias), but the species has not been collected in either of these places.

Identification.—(Figs 21, 24). Features of its phallic complex allow its easy identification (Fig. 22, apical endophallic valves; Fig. 27, cingulum). Number of spines on hind tibiae: 14.

13. Xyleus gracilis (Bruner 1905) (Figs 21, 22, 25, 27, 37, 46, Table 15)

Taxonomy.— Characters of this species have been given with respect to the species-group. Most specimens show dark longitudinal lines on the lateral lobes of the pronotum.

Distribution.—(Figs 37, 46). Very imperfectly known due to its being a rather uncommon species, X. gracilis occurs in central southern Brasil, from the states of Goias and Minas Gerais south to Rio Grande do Sul and the Argentinian province of Misiones.

Identification.— (Figs 21, 25). Its elongated form, low pronotal crest and narrow hind femora, are characters of this species, though some of them are shared with others in the group. Many specimens have the precostal and costal areas of the tegmina, and some also the anal areas, lime green. Others have these areas buff-colored. Below the Sc vein in the costal area, there is usually a narrow white longitudinal band that in most specimens is very conspicuous. Along the M and Rs areas most specimens have a fuscous band that in some individuals is continuous; in others it is fractioned into a series of separate fuscous spots. M and R veins usually show some whitish parts, separated by fuscous tracts. The pronotal disc in some specimens is of a uniform buff or cinnamon color; in other specimens a narrow medial area that includes the crest is fuscous, the lateral parts buff or sometimes of a dirty lime green. One female specimen in the series examined is quite melanic, covered with irregular fuscous markings on a buff background. Some specimens have a narrow line at the top of the pronotal crest and on the lateral carinae of the pronotum, of a much lighter shade than the rest of the pronotum. Some have also the first anal vein of a very light color, contrasting with that of the rest of the tegmen. In the hind wings, the base of the anal area is colored in shades of rose to ruby. The phallic complex offers as usual the best characters for the identification of this species: the shapes of the cingulum (Fig. 27) and of the apical endophallic valves (Fig. 22) are characteristic. Number of spines on hind tibiae: 15 to 18.

14. Xyleus pirapora n. sp. (Figs 21, 22, 26, 27, 45, Table 16)

Taxonomy.— As said with reference to the Attenuatus Species Group, X. pirapora seems the most divergent from the rest of the species in the group, and some similarities with the other species may not be related to a phyletic relationship.

Distribution.— (Fig. 45). The only known specimens are from the country surrounding the town of Pirapora, on the San Francisco River, in central Minas Gerais, Brasil.

Identification.—(Figs 21, 26). This is species with a rather low but arched pronotal crest. The whole insect is rather uniformly colored in shades of chestnut, with a conspicuous longitudinal band of a very light color (very light buff to dirty white) in the costal area of the tegmina, next to and along the Sc vein. Individuals of this species do not have dark longitudinal bands on the lateral lobes of the pronotum. Some have the central area of the pronotal disk colored in a much darker shade than the lateral areas, but in others the whole disk is uniformly colored. Best characters for identification are in the phallic complex, where cingulum (Fig. 27) and apical endophallic valves (Fig. 22) are characteristic. Number of spines on hind tibiae: 9 to 10.

15. Xyleus laufferi (Bolivar 1891) n. comb. (Fig. 43, Table 17)

Taxonomy: identification.— The species is known only from the female holotype, which is practically identical to females of X. attenuatus, X. gracilis and X. araguaia. Only by finding a male in the general area where the female type was collected could it be ascertained if this taxon is conspecific with any of these species. In this case, such a species will fall as a synonym of X. laufferi, this name having priority over the other 3. But the species in this group being so much alike (except in their phallic complex), it might well be that the X. laufferi male will prove to be different from any of the 3 species named above. Without the knowledge of the phallic complex of this species, even its placement in the present Species Group, based only in its external aspect, must be considered as tentative.

As to the possibility of one or the other species being identical with laufferi, geographical reasons would point to X. attenuatus as the most probable, its range lying more to the west, hence closer to Cumbase. On morphological grounds however, a very slight evidence points the other way: X. attenuatus has a lower number of external spines on its hind tibiae (12 to 14) while X. gracilis has 15 to 18 spines, and the type of X. laufferi has 19.

Distribution.— The only known specimen is labelled as from “Cumbase”, a locality on the eastern slope of the Peruvian Andes.

Insignis Species Group

Includes X. insignis, X. aimara, X. lineatus and X. guarani. These 4 species have in common a high pronotal crest, particularly in the metazona, and the sides of pronotum in dorsal view are rather angulate (Fig. 28). Other details of their external aspect, including color pattern, are different in each species as stated below, with reference to each species. The group is admittedly rather heterogeneous, and has been made mainly on the basis of the shape of the apical endophallic valves (Fig. 29), which are narrow, elongated and upwardly directed in their apical parts. The same general cingulum shape is shared by X. insignis and X. aimara, but differs from that of X. lineatus and X. guarani, which also differ in cingulum shape from each other (Fig 27).

16. Xyleus insignis (Giglio-Tos 1894) (Figs 27, 28, 29, 30, 44, 46, Table 18)

Taxonomy.— This is a most variable species in colors and color pattern. Females vary from uniformly lime green to the most diverse patterns of brown, fuscous and umber. These colors may be uniform or with numerous dark spots or markings on a lighter background color. Males are rarely green: most of the ones examined were colored in shades of brown, russet or fuscous.

Distribution.—(Figs 44, 46). A common and abundant species distributed in central western Brasil (Mato Grosso), eastern Bolivia, northern and central Argentina to Entre Rios.

Identification.—(Figs 28, 30). The safest way to identify this species is by examination of the phallic complex (Figs 27, 29). However, some general indications may help in identifiying females or undissected males. Uniformly lime-green males or females are of this species. This uniformly green coloration is much more common in females than in males. Many female collection specimens are uniformly light buff, but I do not know whether these represent green females discolored after death, or originally of this color. An interesting character found in individuals of this species is that the R-vein in the tegmina is frequently either entirely or in parts of a very light color (sometimes almost white); this is very noticeable on a generally much darker background, but is also seen in other species. What allows certain identification in males is their phallic complex: this cannot be mistaken for that of any other species in the genus. Both the cingulum and the apical endophallic valves (Figs 27, 29) are of the most characteristic form, different from those of any of the species mentioned to this point. The cingulum and the apical endophallic valves are somewhat similar to those found in X. aimara. The apical endophallic valves, with their narrow and elongated form, have a certain similarity too with those in X. lineatus and X. guarani; but the cingulum in the latter species is quite different from the one in X. insignis and X. aimara, and is rather of the form found in the species of the Discoideus and Laevipes Species Groups. Number of spines on hind tibiae: 10 to 11.

Note on the coloration of specimens: among 70 females from Mascasin, Prov. La Rioja, Argentina, 43 are green and 27 brown; for males from the same locality, 3 green, 19 brown.

17. Xyleus aimara n. sp. (Figs 27, 28, 29, 31, 44, Table 19)

Taxonomy.—The single male type of X. aimara seems hardly separable from males of species in the groups Insignis or Laevipes. Also, by examination of a single specimen, it would be difficult to define differences or similarities with other species that look like it in general aspect and coloration. Its phallic complex, on the other hand, is quite characteristic, as shown by Figs 27 (cingulum) and 29 (apical endophallic valves). As said above, the phallic complex in X. aimara shows a close relationship with X. insignis.

Distribution.— (Fig. 44). This species is not known except for the type-locality, a seemingly inhospitable tract of the Andean altiplano in the vicinity of the city of Sucre.

Identification.— (Figs 28, 31). The only safe way to identify this species in the light of what is known of it, seems by examination of its phallic complex (Figs 27, 29). Ten spines occur on each hind tibia.

18. Xyleus lineatus (Bruner 1906) n. comb. (Figs 27, 28, 29, 32, 45, Table 20)

Taxonomy.—This species is, in its external aspect, very similar to X. pirapora and X. goias. Judging from characters of their phallic complex however, these 3 species belong in different species-groups: while X. lineatus belongs in the Insignis Group, X. pirapora is a member of the Attenuatus Group, and X. goias of the Laevipes Group.

Distribution.—(Fig. 45). This is a rare species. The limited series now at hand indicates that it inhabits central western Brasil (Mato Grosso, Goias) south to Sao Paulo, and also eastern Paraguay and northwestern Argentina. The limited series now at hand has been found within this large territory.

Identification.— (Figs 28, 32). Specimens of this species have a conspicuous light-colored band occupying the whole of the costal area (between C and Sc) of the tegmina, but this character is shared with specimens of X. goias and X. pirapora. This light-colored line is usually of a very light cream color, sometimes almost white, the basis of its specific name of lineatus. Above this line, veins Sc and R are a very dark maroon or chestnut color, though the R vein has frequently some small whitish sections. The rest of the tegmen, as with usually the rest of the insect, is generally in shades of chestnut or hazel, but in some individuals there is a series of indistinct spots, slightly darker than the background along the R and Rs areas. In 3 of the specimens examined, the precostal and anal areas of the tegmen are of a dirty lime-green color. Accurate identification of the species can be done only by examination of its phallic complex, of which both the cingulum (Fig. 27) and the apical endophalic valves (Fig. 29) are quite characteristic. Number of spines on hind tibiae: 10 to 11.

19. Xyleus guarani (Rehn 1907) n. comb. (Figs 27, 28, 29, 33, 45, Table 21)

Taxonomy.— While X. guarani and X. regularis are almost identical in their external aspect and color pattern, their phallic complexes are quite different, to the point that these species are considered here as members of two different Species Groups: X. guarani being maybe the most divergent species of the Insignis Group, but related to it by narrow and elongated apical endophallic valves; X. regularis being the most divergent species of the Laevipes Group. Examination of both cingulum and apical endophallic valves does not reveal any affinity between these 2 species.

Distribution.— (Fig. 45). This is a rare species, known from western central Brasil (Goias, Mato Grosso), São Paulo and eastern Paraguay, sympatric with its sibling X. regularis.

Identification.—(Figs 28, 33). As said with respect to X. regularis, the external aspect of X. guarani (Fig. 33) does not allow the separation of these 2 species. Background is buff to clay color, on which are many irregular dark (fuscous or umber) markings. A few specimens have the anal (dorsal) area of the tegmina greenish (shades of lime green). Conspicuous in all specimens is a series of dark (umber) subquadrate markings on the M and Rs areas; these markings neatly defined on the M area, become fainter on the Rs area and gradually vanish towards the tip of the tegmen; their numbers are somewhat variable, but are usually 4 to 6 in males, 7 to 8 in females. Cingulum (Fig. 27) and apical endophallic valves (Fig. 29) are characteristic. Number of spines on hind tibiae: 9 to 10.

Incertae sedis

20. Xyleus camposi (Bolívar 1909) n. comb. (Figs 35, 40, Table 22)

Taxonomy.— I see no reason to consider this species as belonging to a genus different from Xyleus. It probably represents the only short-winged species of the genus. As to its affinities, both its general aspect and geographic origin suggest its belonging in the Discoideus Species Group.

Distribution.— The species is known from a few female specimens collected in Posorja, Ecuador, Prov. Guayas, at the northern edge of the Gulf of Guayaquil.

Identification.— A very distinctive species within the genus due to its being brevialate. Its general shape can be seen in Fig. 35. In dorsal view, the prothoracic metazona has its sides rounded as in rosulentus and mexicanus. The male of this species is unknown.

21. Xyleus tuberculatus (Palissot de Beauvois 1817) n. comb. Nomen dubium, nomen oblitum

The figure in Palissot de Beauvois' paper apparently represents a species of Xyleus, but the observable details do not allow assignation to a definite species. Its strongly maculated tegmina suggest a species of the Discoideus Species Group.