486 



7. Small species, 1.5 mm.-l.75 mm 4. flavellus. 



— Larger species, 3-3.5 mm 5. confusus. 



8. Scape of antenna? black, base of flagellum yellow, the remainder pale 



brown; thoracic vittae, lower half of pleurae, the scutellum, and 

 postnotum greenish black, contrasting strikingly with the whitish 

 green abdomen 6. pusio. 



— Scape of antennae yellow ; thoracic vittas pale ferruginous or indis- 



tinguishal)le ; thorax and abdomen yellow or greenish yellow 



7. tenuis. 



9. Thorax entirely black, wholly or partly glossy ; legs entirely pale 



yellow 10 



— Thorax yellow or greenish, the spaces l^etween the vittffi always 



noticeably paler than the vittae ; or legs brownisli 12 



10. Small species, 2.5-3 mm. in length ; abdomen pale green ; basal 



joint of fore tarsi more than one half longer than fore tibia?; 

 hypopygium as in Figure 8, Plate XXXVI 8. viridiventris. 



— Larger species, more than 4 mm. in length ; al)domen black, with or 



without pale posterior margins to the segments; basal joint of fore 

 tarsi less than a fourth longer than fore tibiie 11 



11. Abdomen usually with yellow posterior margins to the segments; 



apical portion of lateral arm of hypopygium black or l)lackish 

 brown and not as long as basal portion 9. ohcdiens. 



— Abdomen entirely black except the apical portion of lateral arm of 



hypopygium, which is yellow and noticeably longer than basal por- 

 tion 10. flavicauda. 



12. Basal joint of fore tarsi less than one half longer than fore tibia?. . . 



13 



— Basal joint of fore tarsi more than one half longer than fore tibia? 



15 



13. Basal joint of fore tarsi nearly one half longer than fore tibiae 



(48: 33) ." 11. jyolitus. 



— Basal joint of fore tarsi at most one fourth longer than fore tibis 



14 



14. Thorax yellowish, vitta? brown ; abdomen green ; proportions of fore 



tibia and basal joint of fore tarsi, 20 : 25 12. miiticus. 



— Thorax brown, vitta? glossy black; abdomen black; proportions of 



fore tibia and basal joint of fore tarsi, 35 : 42 13. similatus. 



15. Small species, averaging 2 mm. in length ; distance from base of 



first vein to cross vein about half as long as distance from cross 

 vein to apex of wing (20 : 41) 14. exiguus. 



— Larger species, averaging 3 mm. ; distance from base of first vein to 



cross vein distinctly more than half as long as distance from 

 cross vein to apex (35 : 50) 15. diihius. 



16. Thorax and abdomen black 17 



— Thorax and abdomen yellow or greenish, the former sometimes with 



dark vittae .' 20 



