746 CLASS IV. INSECTA. 



and pastures, where they sometimes swarm. The number of species is 

 very great. Tipula, Phalacrocera, Cylindrotoma are amongst the British 

 genera. 



Fam. 10. Bibionidae. Fairly large flies, weak on the wing. Antennae 

 short and stout. The male has very large eyes, and there are three 

 ocelli. The larvae are almost caterpillar-like, with a distinct, chitinous 

 head and sometimes with a number of spines on the body. They live 

 frequently on decaying vegetable matter. Bibio often occurs in large 

 numbers in England in the early spring and summer. Scatopse is said to 

 breed in drains, etc. In some species there is a marked sexual difference, 

 the females being red or yellow, the males black. 



Fam. 11. Simuliidae. Small flies with a " humped " thorax. Broad 

 wings, short legs, antennae with no hairs. No ocelli. These flies, all in- 

 cluded in the one cosmopolitan genus Simulium, are known as sand- 

 midges or buffalo-flies. The eyes are enormous in the males. The females, 

 which often occur in large swarms, eagerly suck blood, and so voracious 

 are they that poultry, cattle and even man have been known to succumb 

 to their combined attacks. The larvae are aquatic and live in running 

 water : they spin pupa-cases under water from which the images emerge 

 and float to the surface, each surrounded by a bubble of air. 



Fam. 12. Rhyphidae. A discal cell present in the wings, which are 

 broad and rounded. The species of this family of two or three widely 

 distributed genera resemble miniature Tipulids. The larvae live in 

 decaying plants, cow-dung and foul water. Bhyphus fenestralis frequents 

 window-panes. 



Group 2. BRACHYCERA. 



Antennae variable, usually with three distinct segments, rarely with more 

 than seven : either an arista is present, or the flagellum terminates in a slender, 

 indistinctly segmented, appendage. Palpi one- or two-jointed. Larvae 

 usually maggots with retracted head. 



Fam. 13. Stratiomyidae. Stout flies with three-segmented antennae 

 with a terminal portion of obscure segments frequently bearing an arista. 

 Tibiae not spined. Wings smallish with nervures better developed 

 anteriorly than posteriorly. A large, varied and rather ill-defined family 

 of about one thousand described species, some fifty of which are British. 

 The body is often marked with yellow and green or metallic tints, and is 

 not hairy. The larvae are aquatic or live in damp earth or moss. The 

 pupa is formed inside the last larval skin, and floats in water or is sub- 

 terranean. Stratiomys is sometimes called the soldier-fly. 



Fam. 14. Leptidae. The Snipe-flies are slender with spotted or velvety 

 bodies. Antennae with three joints ending in a bristle. Large wings. 

 They move slowly and are easily caught. They prey on small insects, and 

 the larvae which are often subterranean are also predaceous. The pupae 

 are protected by earthern cells. Atherix. 



Fam. 15. Xylophagidae. Antennae longer than in Leptidae and with 

 a complex third joint. These flies are slender and live on the sap of plants. 

 Their larvae live under bark and suck the juices of other insects. Rha- 

 chicerufi. 



Fam. 16. Coenomyiidae. Thick, heavy flies. Larvae living in 

 burrows in the earth, generally near decayed logs. Only one genus 

 Coenomyia, which is found on both sides of the Atlantic. 



