NOTES ON THE NEARCTIC NUSA (DIPTERA, ASILID^). 



W. L. McAtee. 



During a study of the species of Lapliria occurring north of 

 Mexico, enough was learned also of the species of Nusa inhabit- 

 ing that region to extend our knowledge of the group — informa- 

 tion that has never been summarized. Niisa may be recognized 

 as a genus, not on the principal character advanced in the 

 original description,* closure of first posterior cell, which is 

 sometimes true, sometimes not, but upon the grounds of 

 habitus,, and characteristic genitalia. Nearly all the species 

 have well developed pruinose markings on thorax, including 

 three pairs of lateral lunules and one to three longitudinal 

 vittse. The male forceps are short and one or both pairs of 

 claspers are exposed beyond apex of forceps, seeming a con- 

 tinuation of them. The male hypopygium is thus quite distinct 

 from the types exhibited by the nearctic genus to w^hich Nusa 

 is most closely allied, that is Laphria, in which the apex of the 

 forceps itself is expanded and variously modified, and nearly 

 or quite conceals the claspers. In some species of Nusa the 

 femora are swollen and tibiae curved; in others these characters 

 are not pronounced. 



Key to the Species. 



a. Only apex of abdomen yellowish to reddish. 



b. Length over 20 mm.; genitalia as in Figure 1 criienta n. sp. 



bb. Length less than 20 mm.; genitalia as in Figure 2 fulvicauda Say. 



aa. More of abdomen so colored. 



c. Sides of abdomen black, wings distinctly marked, genitalia as in Figure 3. 



sicaria n. sp. 



CO. Abdomen without black markings, wholly yellowish to reddish; genitalia 

 as in Fig. 4 abdominalis Brown. 



Nusa cruenta new species. 



A black species with seventh abdominal segment and hypopygium 

 reddish testaceous; exposed membranes of abdomen same color and 

 halteres somewhat paler. Thorax apparently entirely without pruinose 

 markings; though this may be due to methods of preparing this individ- 

 ual specimen. Bristles on facial prominence black, remaining pubes- 

 cence of head, coxae, and lower surfaces of legs, long, copious, grayish. 



* Walker, Francis. Insecta Saundersiana or characters of undescribed insects 

 in the collection of William Saunders, Esq., F. R. S., F. L. S., etc. Vol. I, Diptera, 

 1856, p. 105. 



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