310 MEDICAL ENTOMOLOGY 



THE ACALYPTERAE 

 FAMILY SEPSIDAE 



Small ant-like flies of a black or amber colour. Head globular in 

 shape; proboscis and antennae short. Abdomen slender and narrowed 

 at the base ; male genitalia prominent. Subcostal or auxiliary vein dis- 

 tinct or united to the first vein ; anal and basal cells distinct. 



The Sepsidae are commonly seen in the tropics on dung of all kinds ; 

 at first sight they may be mistaken for winged ants on account of their 

 characteristic shape, the abdomen being narrowed at the base. In 

 India they are extremely common on cow dung and may often be seen 

 in swarms dancing and flitting about on its surface ; their irridescent 

 wings and the quaint attitudes they assume make them very striking 

 objects. Their larvae can, as a rule, be recovered in large numbers from 

 the dung on which the flies are feeding, and may be recognized by the 

 presence of two prominent spines at the posterior end. If disturbed they 

 have the habit of inserting their mouth parts into notches on the last 

 segment, and by suddenly releasing them propel themselves four or five 

 inches. 



In Madras two species of Sepsis are infected with flagellates, one with 

 a herpetomonas and, crithidia, and the other with the crithidia alone ; in 

 the Soudan, Roubaud has found another species infected with a herpeto- 

 monas. It is interesting, in view of recent controversies, to note the 

 presence of a true crithidia in a purely dung-feeding insect. 



FAMILY CORDYLURIDAE 



Medium-sized grey to black flies. Head globular ; both sexes dichoptic. 

 Wings large; auxiliary vein always distinct, basal cells large and 

 complete. Squamae small, with the upper one concealing the lower. 

 Abdomen with more than four visible segments. 



Cordylurids are common about decaying vegetable and animal matter, 

 and especially near foul water ; many of the species of Scatophaga may be 

 seen on cow dung. The species are of practical interest in that they 

 may be infected with flagellates of the genus Herpetomonas. The 

 Cordyluridae may be distinguished from the Anthomyidae, many of which 

 have the same habits, by noting that the squamae are always small in 

 the former and the male eyes are widely separated ; in the latter the 

 squamae are large and the male eyes are much closer together. 



