CHAPTER VII. 



Family HIPPOBOSCID.E. 



PLATE XIII., FIGS. 98-100. 



Apart from structural characters, the strange-looking flies 

 belonging to this family differ from all those previously dealt with 

 in two peculiarly important respects, namely in their mode of life 

 and method of reproduction. Instead of flying about freely like 

 other blood-sucking flies, and as a general rule only settling on 

 a Vertebrate in order to feed, the Hippoboscidae are permanent 

 parasites of mammals and birds, seldom leaving their hosts under 

 normal conditions *; stray specimens which occasionally alight on 

 human beings usually at once endeavour to hide themselves in the 

 hair or beard. Secondly, instead of laying eggs, the female 

 Hippoboscid produces at intervals a single full-grown larva, which 

 assumes the pupal state immediately after extrusion. 



In appearance the Hippoboscidae (which vary in length from a little 

 over 3 mm. in the case of a small Lipoptena, to 11.5 mm. in that 

 of a female Hippobosca camelina, Leach, with abdomen distended 

 by its offspring) are flat-bodied, horny-looking flies, with long wings 

 in the known African forms, and powerful legs. While the head as 

 well as the thorax is flattened and shining, the abdomen is sac-like, 

 devoid of the ordinary indications of segmentation, and of a leathery 

 aspect ; this however does not affect the general appearance, 

 since the abdomen is usually entirely or partially concealed by the 

 wings, which when not in use lie closed flat one over the other like 

 the blades of a pair of scissors, as in the Tsetse-flies, and in this 

 position project a considerable distance beyond the end of the body 

 (see Plate XIII., figs. 98, 99). The general coloration of head and 



* In the case of Stenopteryx hirundinis, Linn., and Oxypterum pallidum, Leach, 

 which in the Palaearctic Region are parasitic respectively on the House Martin 

 (Chelidon urbica, Linn.) and the Swift (Cypselus apus, Linn.), the flies are found in 

 the nests as well as on the birds themselves. 



M 2 



