Jr»SYCHE. 



THE INVERTED HYPOPYGIUM OF DASYLLIS AND LAPHRIA. 



BY RORERT E. SNODGRASS, PULLMAN, WASH. 



The Asilid genera Dasyllis and 

 Laphria present the curious anomoly of 

 having the hypopygium, i. e., the ninth 

 segment of the male, inverted. Figures 

 I and lo clearly show this condition in 

 D. grossii and D.flavicollis. 



The writer is indebted to Professor 

 J. M. Aldrich, of the University of Idaho, 

 for named material on which the fol- 

 lowing descriptions are based. 



The hypopygium consists of a large 

 ovate structure carried by its larger end 

 on a comparatively narrow neck formed 

 of the seventh and eightli abdominal 

 segments and their intervening mem- 

 branes (Fig. lo). Within the hypopy- 

 gium is a large cavity, the genital cham- 

 ber, opening posteriorly. It has a thick 

 swollen floor on which is carried the in- 

 tromittent organ, and thin dorsal and 

 lateral walls. The dorsal wall presents 

 a large median notch reaching forward 

 almost to the base of the hypopygium. 

 The lateral walls are similarly, but less 

 deeply, notched. 



The lower part of the hypopygium is 

 the ninth tergum (IX t.). It consists of 

 a large convex plate, oval to elongate- 

 ovate in ventral view, with the smaller 

 posterior end truncate. The posterior 



end may be also deeply notched as in 

 D. grossa (Fig. 4) or it may be but 

 slightly concave as in D. flavicollis and 

 Z. vultur. 



The upper and lateral parts of the 

 hypopygium consist of the ninth sternum 

 (IX s.). On account of the dorsal and 

 lateral notches of the hypopygium, the 

 sternum has tlie form of a basal semi- 

 circular plate with two large dorso-lateral 

 lobes projecting backward (Figs, i, 2, 4 

 and 10, IX s.) Each of these lobes 

 carries, within the genital chamber, two 

 pairs of large movably attached ap- 

 pendages ((7 and /'). One pair {a) is 

 lateral and is articulated to the dorsal 

 edge of the lateral notch of the hypopy- 

 gium (Figs. 1,5 and 10, a). Each of 

 these (Fig. 9) is laterally fiattei'ksd and 

 strongly curved dorsally, where it ends 

 in one or two heavy claws that project 

 out of the dorsal notch. The other pair 

 (/') is dorsal and is born by two lobes at 

 the anterior angles of tlie dorsal notch of 

 the hypopygium (Figs. 2 and 5,/'). These 

 appendages (Fig. 8) vary considerably 

 in shape. They are generally bent some- 

 what laterally. In some species they 

 are expanded basally, in others termin- 

 ally ; in some they are prong-like, in 



