66 ILLIXOIS BIOLOGICAL MONOGRAPHS [236 



EXPLANATION OF PLATE 



Cephalic aspect of the Head 



Fig. 19. Di.va clavata. 



Fig. 20. Tabanus gigantcus, female. 



Fig. 21. Tabanus gigantcus, male. 



Fig. 22. Proiuachus vertebratus. 



Fig. 23. Eristalis tenax, female. 



Fig. 24. Eristalis tenax, dorsal end of the tormae. 



Fig. 25. Eristalis tenax, male. 



Fig. 26. Psorophora ciliata, male. 



Fig. 27. Stratiomyia apicula, male. 



Fig. 28. Stratiomyia apicula, female. 



Fig. 29. Exoprosopa fasciata. 



Fig. 30. Mydas clavatus. 



Fig. 31. Aphiochacta agarici. 



Fig. 32. Platypeza velutina. 



•Fig. 2i. Psilocephala haciuorrhoidalis, male. 



Fig. 34. Lcptis vertebrata, female. 



Fig. 35. Lcptis vertebrata, male. 



Fig. 36. Psilocephala hacmorrhoidalis, female. 



Fig. 37. Lonchoptcra lutea, female. 



Fig. 38. PipuncuUts ciiigulatus, female. 



