DIPTEKA OR TEUE FLIES. 231 



run about, pulling the hair, and cause mucli irritation by so 

 doing as well as by blood-sucking : it appears they also suck 

 up the sweat. Like aU Pupipara, the Forest Fly deposits 

 round puparia, which are notched at one end. There is but 

 one larva in the female, which lives there until the puparial skin 

 is formed, when the puparium is laid, the larva inside soon 

 turning to a pupa. In four weeks the fly emerges from this 

 black case. Animals soon get used to their presence, but a 

 strange horse will become most restive when they settle upon 

 it, especially when (as often happens) the belly is attacked. 

 Little can be done to keep them off, except sponging the horse 

 over with a paraffin sponge. 



Two other species are sometimes troublesome — namely, the 

 Fowl-fly {Ornithomyia avicularia) and the Bee-louse {Br aula 

 coeea) ; the former a winged species that attacks birds, the latter 

 a wingless reddish-brown insect parasitic on the hive-bee. 



Fleas (Pulicidae). 



Some fourteen species of fleas are found in Great Britain, all 

 partial parasites, living upon animals and birds. Fleas are 

 apterous Diptera which are perhaps more nearly related to the 

 Fungus Gnats (Mycetaphilidce) than to any other Diptera. 

 Pulicidae have a sucking and piercing mouth by which they 

 draw out the blood of their hosts. The body of the flea is 

 flattened from side to side, and the legs are well developed to 

 enable them to perform their hopping motions. Some have com- 

 pound eyes {Pulex avium and P. irritans), others have none (P. 

 ohtvsiceps, &c.) The eggs or "nits" are laid in dust and dirt, 

 and the larvae are pearly-white fourteen-segmented grubs, with 

 a large brown head, and pupate where they live, as small brown 

 chrysalids. The larvae are said to be fed by the mother. Some 

 feed on scurf, hairs, feathers, and other epidermal productions. 

 Many of the species can be easily identified by the number of 

 spines in the curious comb-like structure on the pro thorax. 



