63 
British Islands includes two other species of Hippoboscidae, 
Stenopteryx hirundinis, Linn., and Oxypterum pallidum, Leach, found 
respectively on and in the nests of the house martin {Chelidon urbica, 
Linn.), and the swift {Cyp.selns apus, Linn.). 
It is doubtful whether an authentic instance exists in which any 
species of Hippoboscidai has sucked human blood under natural 
conditions, though the flies sometimes stray on to human beings 
when their hosts are interfered with. 
Genus 
HIPPOBOSCA, Linnaeus. 
Hippobosca equina, Linn.— The Forest Fly. 
Plate 31. 
The upper figure shows the resting position. 
As indicated by the English name, the principal home of this 
species in the British Islands is the New Forest, in Hampshire, where 
it may often be seen in clusters like bees, sometimes numbering many 
hundreds, on the ponies and cattle which run wild there. The flies 
chiefly congregate on parts where the skin is thinnest, beneath the 
tail, on the perinaeum, and on the inner surface of the thighs. The 
bite does not seem to cause pain, and animals bred in the Forest take 
no notice of the fly, but strange horses and especially donkeys are 
sometimes driven almost frantic by the irritation caused by a single 
Forest Fly crawling over them. The toothed claws enable the fly to 
cling so tightly to the hair that it is impossible for an animal to 
dislodge it by a brush from its tail, and the quick and somewhat 
crab-like movements of the insect, which when disturbed usually 
moves sideways, tickle the host and are exceedingly irritating to 
sensitive animals. 
Forest flies are to be found from the beginning of May until at least 
the second week in October. In addition to the New Forest the species 
