The life history and case-making behavior of Phylloicus ornatus (Banks) from two spring-fed first-order streams in the Edwards Plateau bioregion of Texas were studied from January 1998 to November 1999. Field sampling of larvae, pupae, and adults, and laboratory rearings indicated a multivoltine cycle. Eggs averaged 0.32 mm diameter and have distinctive, ridged chorionic sculpturing. First instars differ from late instars in having fewer labral setae and a unique spur-like claw on each lateral hump. Larval development was asynchronous, with second through fifth instars and pupae present most months. First instars were present April through July, October, and November. Case-making of first instars, and case reconstruction of later instars extracted from their cases, was documented by videotape. The chronological aspects of case-building behavior of first and later instars are documented. Case-building was compared with that of two other species in other families. The near-identical sequences suggest that case-making behavior in all three species represents a recapitulation of evolutionary events leading to larval case-making in Spicipalpia and Integripalpia.