204 IOWA ACADEMY OF SCIENCES. 



Color: Soiled white to light fuscous above; tip of vertex ivory white; 

 triangle with a black margin, line near the margin before- the ocelli; rec- 

 tangular spot on disk, an oblique spot at base of vertex, as in D. in£atus 

 well marked, brown. Pronotum soiled white with faint indications of 

 stripes; elytra sub-hyaline, soiled yellowish-white, oblique band reduced to 

 two spots, one on the clavud near the pronotum, the other between the first 

 and second sectors unequally divided by the white cross nervure; apical 

 and refiexed veinlets broadly white, darkly lined before as is also the outer 

 apical margin; tergum broadly black at base, lined near tip; outer pair of 

 lines approximate bahind. Below upper half of face sharply black, light 

 arcs more or less distinct; lower half sharply white; venter fuscous. 



Genitalia: Ultimate ventral segment of female about half as long as 

 broad, margin roundingly produced in the center, notched. Disk light, 

 produced part black, pygofers broad, short, brown, maculate with white. 

 Male valve broad, obtusely pointed; plates broad at base, concavely, attenu- 

 ately pointed, three times the length of the valve, equaling pygofers. 

 Described from numerous specimens. 



Larvce resembling those of albidus in form and sayi in color, but with 

 more definite stripes. Upper half of the face black. 



Vertex: Sides acutely angled, point obtusely rounded; body slender, 

 tapering, last abdominal segment, long, narrow. Color above, striped with 

 olive and white, a narrow median white line from tip of vertex to the tip of 

 abdomen slightly expanded on the last segment, a slightly wider light line 

 margining the vertex next the eye on either side and running t© the pos- 

 terior margin of the penultimate segment of the abdomen; a narrow white 

 margin on either side from behind the eyes to the last abdominal segment 



The pupae have a small round spot in the outer light line near the anter- 

 ior margin of the thorax and a larger oblique mark near the posterior 

 margin of the wing-pads; base of both rows of hairs on the abdomen 

 with small round white spots. Below: Face, upper halt black, lower half 

 sharply white, as in adult, the dark line continuing along the fermora and 

 connecting with them as in abidus larvEe. 



This species and the three following strongly resemble each 

 other. They are most accurately separated by the structure 

 of the genitalia, which have proved to be very constant in the 

 hundreds of specimens studied, as in fact they have for the 

 whole genus, though tested by the study of nearly 5,000 speci- 

 mens. It has been collected in abundance at Ames this season, 

 and one Colorado example received from Professor Gillette. 



It was taken for the first time, June 3rd, when it occurred as 

 full-grown larvae and adult males. By the middle of June the 

 larvsB had disappeared and the adults were numerous, continu- 

 ing so well into July. Small larv£e were found the third week 

 in July, and from then on they were numerous until the second 

 week in August, when they had become full grown and begun 

 to disappear. The adults appeared by the end of the first week 

 in August, becomiog abundant by the middle and continuing to 



