INTRODUCTION 27 



in fungi ; the Tabanidce or gad flies, many of them annoy- 

 ing and even harmful to stock in fact they are proved 

 carriers of disease in animals ; and the robber flies or Asilidce, 

 almost bee-like insects which earn their livelihood by killing 

 other insects, often much larger than themselves. 



Of the CyclorrapJia, we may mention the Syrphwkv or 

 hover flies, common objects as they remain, apparently 

 motionless, though in reality with rapidly vibrating wings, 

 over some favoured flower which they are visiting for the 

 sake of its pollen or nectar : some of the aquatic larvae of this 

 family have curiously long breathing tubes, hence their name 

 of rat-tailed larvae. The best-known member of the family 

 Sepnidtv is the cheese skipper, whilst the families Oscinidce 

 and Trypetidcv supply many enemies of the farmer and 

 gardener. The CEstridce or bot flies comprise species 

 attacking man and animals ; the Tachinidce are all parasitic 

 in the larval stage on other insects, particularly lepidopter- 

 ous caterpillars ; the Sarcophagidce or flesh flies and the 

 Antltomyidcv live on carrion and vegetable matter respec- 

 tively : to the latter family belongs the lesser house fly. 

 The Miiscidce is the most important family of all ; it is sub- 

 divided into blood -sucking and non-blood-sucking flies. To 

 the latter division belong the house fly, the blow fly, the 

 green-bottle fly, the screw- worm fly, the Congo floor maggot, 

 and the Tumbu fly ; among the blood -suck ing flies of the 

 family the most notorious are the tsetse fly and the stable 

 fly. Other important dipterous families are the tick flies 

 or Hippoboscidce, of which the best known is the sheep 

 tick ; all the members of the family are parasitic on mammals 

 or birds, whilst the parasitic flies of the bats all belong to 

 the family Nycteribiidcc. 



(h) Thysanoptera (tassel wings), thrips, etc., with four 

 very narrow wings fringed with hairs. Their mouths, 

 though weak, are adapted for biting. 



(i) Rhynchota (beaked insects), bugs, scale insects, etc., 

 with four wings, of which the upper pair may be leathery 



