DIPTERA. 749 



Fain. .'51. Platypezidae. Small flies, with three-segmented antennae 

 and a terminal bristle ; the first two segments are short, the last is longer. 

 The tar*i of the hind legs are very broad. No empoclium. A small 

 family of little, blackish flies which frequent shady places. The larvae 

 have a flattened shape and their edges bear bristles. They live between 

 the " gills " of mushrooms and toad-stools. Opetia, Platycnema, Platy 

 peza and Callomyia are the four genera with British species. 



Fani. 32. Pipunculidae. Small flies with very short antennae with 

 a non-terminal bristle. The head is very large, nearly spherical, and 

 composed almost entirely of the enormous, almost contiguous, eyes. A 

 small family with three British genera and perhaps twelve species. The 

 larvae live parasitically within the bodies of Homopterous Hemiptera 

 When about to undergo transformation, they emerge from their hosts, 

 and pupate within the last larval skin, usually in the ground, occasionally 

 exposed on leaves. Pipunculus. 



Fam. 33. Conopidae. Abdomen pedunculated like a wasp's and often 

 yellow-banded. The head is large and swollen. Few or no bristles on 

 the dorsal surface. Not a very large family, some members of which, 

 e.g. Conops, pass their larval life inside the abdomen of Bumble-bees. 

 Wasps, etc. 



Fam. 34. Syrphidae. Stoutish flies with fleshy, retractile proboscis, 

 recognizable by the presence of an extra longitudinal nervure, the " vena 

 spuria," between the third and fourth. Head and eyes large. The 

 family is large and cosmopolitan. The Hover-flies vary much in colour 

 and many of them resemble Hymenoptera ; they frequent flowers and may 

 often be seen hovering in the sunlight. The habits of the larvae vary. Those 

 of Syrph us devour plant lice. Volucella larvae live in bee- and wasp-nests, 

 eating the grubs of their host. Others feed on decaying vegetable matter 

 or wood. The rat-tailed maggot of Eristalis lives in foul water, or 

 possibly even in carcases. The curious mollusc-like larvae of Microdon 

 lives in ants' nests. 



Group 4. SCHIZOPHORA. 



Three joints to the antennae and an arista, or bristle not borne ter- 

 minally. An arched 'frontal suture overlies the base of the antennae as a rule. 



This group includes both a large number of families of very small flies 

 which are but little known, and also the most typical of all flies e.g. the 

 Muscidae. The former collection, known as the Muscidae acalyptratae, 

 are divided into a number of families of varying valency, and they 

 eminently require revision. They are called " acalyptrate " because the 

 squama is either absent, or when present does not cover the halter. They 

 will be barely mentioned here. 



Fam. 35. Doryceridae. The larva of Dorycera burrows in the leaves of 

 aquatic plants. 



Fam. 36. Tetanoceridae. The larvae are said to have but eight seg- 

 ments. 



Fam. 37. Sciomyzidae. Brown or greyish unattractive flies which 

 haunt high grasses and bushes. 



Fam. 38. Celyphldae. In Celyphus the enlarged highly polished 

 scutellum overhangs and hides the abdomen, which is much reduced, 

 and also the wings. 



Fam. 39. Sepsidae. Small, polished, flies breeding in dung or 



