Entomology of the Illinois Rixier. 237 



fields in Champaiga county. The dates given are May 

 31 and June 4. Examples were placed in a breeding- 

 cage, and an imago of costalis was secured from them. 



The imago, known as the "green- head, "is very generallj' 

 common, and is quite a pest in some bottom-land prairies. 

 A few examples were noted along shore at Station D Aug. 

 20. The examples in our collection were taken on twenty- 

 two occasions, all between July 15 and Aug. 13 except 

 three dates, July 8 and Aug. 18 and 31, which would 

 make it probable that it is single brooded. The localities 

 are Carroll, Lake, Cook, and Ford counties at the north, 

 and Fulton, McLean, and Champaign counties in central 

 Illinois. The specimens were from a variety of situations, 

 usually in low herbage, often taken visiting flowers. 



Larva.— luQix^th. 20 mm., diameter 2.7 mm. Prothorax 

 with lateral shining areas about as long as the dorsal, 

 coarsely striate, a smooth spot near center of disk ; 

 dorsal and ventral areas of thorax smooth, a few 

 striae on those of metathorax, especially posteriorly; 

 remaining areas moderately striate, lateral areas of 

 abdomen a little more finely striate than the others; all 

 more or less shining. 



Dark annuli pale, narrow, longitudinal stripes scarcely 

 present; false feet with dull pubescent crests, their 

 sides rather finely striate; a narrow dark annulus at 

 base of respiratory tube, another around base of last 

 segment, enclosing anal prominence and giving off a 

 pair of lateral stripes, the lower one longer; no project- 

 ing spine seen. 



Pupa (from defective cast skin of male).— Length 20 

 mm., diameter 3 mm. Light fuscous brown, shining; 

 abdomen smoothly wrinkled, ^ lightly opaque ;prothoracic 

 spiracular tubercles slightly but nearly equally elevated, 

 free margin rounded at tip, rima not vertical, evenly 

 arcuate, slightly hooked in front. 



Abdominal spiracular tubercles small, subtriangular, 

 narrower behind, obliquely subconical, much shorter 



