318 ARTICULATA: INSECTA. 



bovis, Fabr.) lays her eggs on the backs of the cattle, and 

 the larvae penetrate the skin and live there in open sores. 

 Another species (Ceplialomyia, ovis, Linn.) lays her eggs 

 in the nostrils of sheep, and the larvae crawl into the cavi- 

 ties of the head, and in many cases produce death. 



But by far the largest group of all the Diptera is that 

 which Latreille called the Muscidae, which includes about 

 one-third of all the members of this sub-order, and which 

 are known under the popular names of House-flies, Flesh- 

 flies, Blow-flies, Cheese-flies, etc.* Meigen has already, a 

 long time ago, described 1,700 species of these flies as be- 

 longing to Europe, and there is probably even a greater 

 number in this country. These flies have a wonderful 

 power of reproduction. Some species, as the Flesh-flies, 

 are viviparous. Reaumur found 2,000 larvae in a single 

 specimen of this sort. 



Among the Diptera there are some anomalous forms. 

 One of these is seen in the Fleas or Pulicidae, which are 

 wingless flies with hard, compressed bodies, with two sim- 

 ple eyes instead of compound eyes, a sucker-like arrange- 

 ment of mouth-parts, and hind legs specially adapted for 

 leaping. By many writers the Fleas are regarded as con- 

 stituting a distinct order called the APHANIPTERA, from 

 the Greek aphanizo to hide, &.r\d.pteron a wing. 



Other anomalous forms are seen in the Horse-ticks 

 (IIippobosea\ Sheep-ticks (Mellophaga), Bird-ticks (Orni- 

 tJionnjici), etc. These have a horny, flattened body, flat 

 head, large eyes, rudimentary antenna?, and a proboscis 

 formed by the labruin and maxillae. They are parasites, 

 and differ from all other insects in their mode of develop- 

 ment. Each female produces only one or two larvae, and 

 when first hatched the larva is not divided into rings, but 



* Tor a full account of the House-Fly, see Packard " On the Transforma- 

 tions of the Hoiisc-Fly." 



