344 The Ohio Naturalist. [Vol. XI, No. 7, 



attenuated and curved forward so as to reach the anterior margin 

 of the segment. The band on the fourth segment also touches its 

 anterior margin in the middle, while that on the third is more 

 remote from the anterior margin; the black interval between the 

 bands is twice as broad as the bands. The fourth and fifth seg- 

 ments have yellow posterior margins, the fifth usually with two 

 yellow spots on each side at the anterior margin. 



Male. "Similar to the female but abdominal cross bands 

 broader, the biconvexity on their hind side stronger, and the 

 sinus in the middle deeper; the gray spot on the cheeks under the 

 eye often larger, sometimes occupying a considerable portion of 

 the cheek; the brown ring on the hind tibiae usually expanded so 

 as to reach the tip of the tibiae. The eyes (contiguous) are more 

 distinctly pubescent, the front is beset with yellow pollen except a 

 narrow black space above the antennae." 



Explanation of Plates XVI and XVII. 

 Figures 1-S, Didea fiiscipes Loew. 



Fig. 1. Adult female x6. 



Fig. 2. Larva about six times natural size; a, anterior spiracle; h, caudal 



spiracles. 

 Fig. 3. Antero-ventral view of head and mouth-parts of larva, enlarged; 



a, upper jaw with a small pair of hooklets at the side; b, lower 



jaw; c and d, lateral hooklets; e, antenna;/, sense papillae. 

 Fig. 4. Right anterior spiracle much magnified. 

 Fig. 5. Posterior breathing organs enlarged; a, one of the radiating 



spiracles. 

 Fig. 6. Dorsal view of puparium a little more than five times natural size; 



a, caudal spiracles. 

 Fig. 7. Puparium from the side showing arrangement of spines and line of 



cleavage for escape of adult. 

 Fig. 8. Head of male in profile. 



Figures 9-16 Syrf^hus lorvus Loew. 



Fig. 9. Adult male natural size and enlarged. 



Fig. 10. Larva natural size and enlarged; a, anterior spiracle; b, posterior 



spiracles. 

 Fig. 11. Antero-ventral view of head and mouth-parts much enlarged; a 



and h, upper and lower jaw partially separated; c, outer pair of 



mouth-hooks; d and e, two inner pairs of mouth-hooklets; 



/, antenna; g, anterior spiracle; h, sense papillae. 

 Fig. 12. Anterior spiracle of larva highly magnified. 

 Fig. 13. Posterior breathing appendages much enlarged; a, one of the six 



caudal spiracles. 

 Fig. 14. Puparium from above natural size and enlarged; a, posterior 



spiracles. 

 Fig. 15. Puparium from side showing line of cleavage for escape of adult. 

 Fig. 16. Head of female in profile. 



