62 
Family 
hippoboscidae. 
The strange-looking flies composing this Family are parasitic 
upon mammals and birds, and are probably descended from 
ancestors belonging to the Muscidae, which underwent modification 
in bodily structure as a consequence of the adoption of a parasitic 
mode of life. The body in all cases is flattened and horny ; the feet 
are provided with accessory claws to enable the insect to cling to 
the hair or feathers of the host ; and while some of the forms, such 
as the Forest Fly (Plate 31), and Ornithomyia avicularia, Linn. 
(Plate 32) are fully-winged, others show a progressive reduction in 
this respect until in the " Sheep Tick " (Melophagus ovinus, Linn., 
Plate 34), the wings are wanting altogether. But even in fully- 
winged forms, since the flies are true parasites, the wings, as a rule, 
are made use of merely in order to reach the host, or, in the case of 
the males, in order to find an individual of the opposite sex, and 
thereafter it is only in exceptional circumstances, such as the death 
of the host, or too active pursuit by the human hand, or when taking 
a short flight from one animal to another, that these flies are ever 
seen upon the wing. The proboscis in the Hippoboscidae is curved, 
extremely slender, and protrusible, but is composed of the same 
parts as that of the blood-sucking Muscidae. In appearance it 
presents a decided resemblance to the proboscis of the Tsetse-flies, 
and it also acts in the same way as the latter, its tip being armed 
with sharp chitinOus teeth which enable the organ to pierce the skin 
of the host. Another point of resemblance to the Tsetse-flies is to be 
found in the mode of reproduction, which is a further development 
of the process seen in the flies referred to, and has caused the 
Hippoboscidae and certain other families of parasitic Diptera 
belonging to the same group to receive the name Pupipara. In these 
forms, namely, the pregnant female does not lay eggs, but produces 
at each birth a full-grown larva, which assumes the pupal state 
immediately after extrusion. 
In addition to those figured in Plates 31 to 34, the fauna of the 
