Aspects of ecology are described for the Yucatán colubrid snake Conophis lineatus concolor, as inferred from examinations of museum specimens and a review of published literature records. Adult males of this distinctive subspecies are larger than females (> 890 mm versus < 760 mm SVL) and at the same body size males also have longer tails, although sexual dimorphism in other proportional features of morphology is negligible. Food habits are diverse; of 29 prey items identified to main taxonomic group, the most important in terms of relative composition (l_x) were lizards (0.394) and arthropods (0.391), followed by squamate eggs (0.061) and thereafter in equal measure by frogs, snakes, and mammals (0.044). More than 90% of the arthropods were engorged cattle ticks, Boophilus microplus, and several snakes had fed exclusively on this prey type. An ontogenetic increase was evident in the proportion of larger prey consumed, although samples were inadequate to allow an assessment of the relationship between prey size and the observed sexual difference in snake body size. Clutch size varied from 5-8, and females appear to have an extended reproductive cycle with oviposition timed to the wet season.