1915] Van Duzee — Dipterous Genus Thrypticus 85 



Most of the species of this genus are difficult to separate except 

 by the hypopygium and its appendages, and great care should be 

 taken to place the specimen so as to get a direct side view of these 

 organs, or the perspective w ill give a very wrong idea of their 

 form. 



In mounting them it is always best to extend the hypopygium, 

 which can be done easily with a pin. 



Some allowance must be made for shrinkage and also for varia- 

 tion in color, but I do not think the variation is great. This paper 

 is based on the study of about fifty specimens. 



TABLE OF NORTH AMERICAN SPECIES. 



1. Femora green (Fig. 2) fraterculus Wh. 



Femora yellow 2 



2. Venter and part of the dorsum of the abdomen yellow 3 



Abdomen without yellow except sometimes on the venter 4 



3. Venter, whole of sixth abdominal segment, antennse and base of hypopygium 



yellow (Fig. 8) cupuliferus Aid. 



Venter, first two abdominal segments, antennse and base of hypopygium 

 yellow (Fig. 1) abdominalis Say. 



4. Hypopygium ovipositor-like, bent under the abdomen singularis Aid. 



Hypopygium normal 5 



5. Fourth vein bent backward to meet the cross-vein, forming a distinct angle 



at this point minor Aid. 



Fourth vein only gently bent at the cross- vein 6 



6. Antennse yellow 7 



Antennae black 8 



7. Capsule of hypopygium truncate at tip (Fig. 3) vietus n. sp. 



Capsule pointed at tip (Fig. 5) muhlenbergice J, & C. 



8. Hypopygial lamella sessile, rounded at tip (Fig. 9) tectus sp. nov. 



Lamella somewhat petiolate 9 



9. Lamella nearly round (Fig. 6) vAllistoni Wh. 



Lamella large, somewhat oval, about twice as long as wide 10 



10. Thorax green with violet reflections and a golden spot before the scutellum 



(Fig. 4) aurinotatus sp. nov. 



Thorax green or purple with the posterior depression green 11 



11. Thoracic dorsum purple, hypopygium rather pointed, lamella pointed 



pusillus Aid. 

 Dorsum of thorax green, hypopygium rounded at tip (Fig. 7) . . comosus sp. nov. 



Thrypticus abdominalis Say. 



Chrysotus abdominalis Say., Jour. Acad. Sci. Philadelphia, VL p. 169. 



Male: Length 2 mm. Eyes nearly touching below the antennae; face green (purple 

 in one specimen); front purple; mouth parts yellow or yellowish brown; antennse 

 and arista yellowish brown; bristles of the head and thorax yellowish. Thorax 



