748 CLASS IV. INSECTA. 



down under the strongly convex, humpbacked thorax. Wings small,, 

 but the squama hides the halteres. The flies are often metallic and 

 brightly coloured. This is a small group with few species, but two 

 genera, represented by Ogcodes gibbosus and Acrocera globulus, are 

 British. The larvae are parasitic in spiders or in their egg-sacs. 



Fam. 24. Lonchopteridae. Slender, minute flies with lance-like wings 

 with feeble nervuration. A small family of very isolated structural 

 characters. The larvae live on the earth under leaves, etc. Lonchoptera, 

 the only genus, is widely distributed. 



Fam. 25. Mydaidae. Large flies, with yellow and red bands and 

 knobbed antennae. Wings with complex nervures, often pigmented. 

 This family is chiefly tropical but reaches Southern Europe, and the 

 American Mydas spreads into the S. United States. The flies are predatory,, 

 and the larvae live in decaying trees and probably prey on wood-boring 

 insects. 



Fam. 26. Asilidae. Large, strong, hairy flies. The proboscis forms a 

 short, stout, murderous beak. The thorax is narrowed in front and the 

 head appears broad. Feet well developed with large claws, pulvilli and 

 bristle-like empodia. The Robber- or Hawk-flies form an enormous 

 family with some 3,000 species. They are amongst the most rapacious 

 of insects, attacking equally wasps, bees, tiger-beetles, dragon-flies, etc. 

 Some of them closely resemble the Hymenoptera on which they prey. The 

 larvae live in the earth or in wood, and feed on Coleopterous larvae 

 and eggs of grass-hoppers, etc. Asilus. Laphria resembles a Vespa. 



Fam. 27. Apioceridae. Medium-sized black and white flies with 

 transparent wings. No empodium. A small family of two genera con- 

 fined to the eastern side of the Pacific and to Australia. They are allied 

 to the Asilidae. Apiocera. 



Fam. 28. Empidae. Smallish, slender, dingy flies, with little or no 

 hair except on the long legs. Predaceous, attacking and devouring 

 other flies. Proboscis long and slender. The ovipositors of the female 

 and the claspers of the male are often conspicuous. This is a family 

 of some eleven hundred species, nearly two hundred of which are British. 

 They frequent woods and dance vigorously up and down in the air,, 

 and some of them carry little webs of silk. The cylindrical larvae live 

 under leaves or in other decaying vegetation. 



Fam. 29. Dolichopidae. Slender, moderately sized or small flies with 

 blue or green or golden metallic sheen. Legs long. Proboscis short and 

 fleshy. A family of about the same size and with almost as many British 

 representatives as the preceding. The males are curiously and diversely 

 ornamented. The larvae live under bark, or amongst decaying plants. 

 The pupa is protected by a cocoon. 



Group 3. ASCHIZA. 



Antennae of not more than three segments, bearing an arista or bristle 

 which may be feathered, and is very rarely terminal. No frontal arched suture 

 over the base of the antennae. 



Fam. 30. Phoridae. Small flies with two very conspicuous dark 

 veins near the front edge of the wings, very convex thorax and two- jointed 

 antennae with a bristle. A small and isolated, but widely distributed, 

 family whose members haunt window panes. The larvae live on a variety 

 of decaying plants and attack also such animals as snails and chrysalids. 

 The pupa case is the last larval skin, hardened. Trineura. 



