418 



— Thorax deep black, not contrasting sharply with base of abdomen, 



the latter with the segments at least partly black or brown 8 



6. Legs yellow, without black markings ; fore tarsi with long hairs, 



basal joint about a fifth longer than fore tibiae 13. nigricans. 



— Legs whitish, fore femora, except the bases and apices, black; fore 



tarsi without long hairs 7 



7. Basal joint of fore tarsi rarely 1.5 times as long as fore tibiffi 



(57 : 38) ; fore and mid coxae and basal two-thirds of fore femora 

 black, remainder of legs whitish yellow 14. fallax. 



— Basal joint of fore tarsi about one fifth longer than fore tibiae 



(78 : 66) ; mid and hind coxae browned, apical half of fore femora, 

 the extreme apices of mid and hind femora, bases and apices of 

 all tibige, and apices of tarsal joints blackened, remainder of legs 

 whitish yellow 15. pedellus. 



8. Fore tarsi with long hairs on their posterior surfaces, the length of 



which greatly exceeds the diameter of the joints which bear 

 them 9 



— Fore tarsi without long hairs 13 



9. Basal joint of fore tarsi not more than a sixth longer than fore 



tibiffi 10 



— Basal joint of fore tarsi at least a fourth longer than fore tibijB. .12 



10. Second joint of fore tarsi shorter than third 16. harhipes. 



— Second joint of fore tarsi longer than third 11 



11. Legs yellow ; basal joint of fore tarsi very slightly longer than fore 



tibige (75:70); hypopygium similar to that of decor us (PL 

 XXXIII, Fig. 11 ) 17. quadripunctatus. 



— Legs fuscous; basal joint of fore tarsi about a seventh longer than 



fore tibiae (80: 70) ; hypopygium as in Figure 6, Plate XXXVIII 

 18. utaliensis. 



12. Basal joint of fore tarsi more than a third longer than fore tibiae 



(92 : 68) ; large species, average length 7.5 mm. ; hypopygium as in 

 decorus (PL XXXIII, Fig. 11) 19. fasciveniris. 



— Basal joint of fore tarsi a fourth longer than fore tibife (45: 36) ; 



small species, average length 5 mm. ; hypopygium as in Figure 4, 

 Plate XXXVI 20. claripennis. 



13. Thorax glossy black or blackish brown, without or with only slight 



pruinescence between the vittae 14 



— Thorax with dense pruinescence between the vittae, sometimes the 



entire surface densely pruinescent, or mesonotum opaque 15 



14. Halteres black; basal joint of fore tarsi a fifth longer than fore 



tibiae (24 : 20) ; hypopygium as in Figure 10, Plate XXXIII 



21. nig roJialter alls. 



— Halteres yellow; basal joint of fore tarsi barely longer than fore 



tibiae (24: 23) ; hypopygium as in Figure 15, Plate XXXIII 



22. subcequalis. 



