AUGUST 175 



peculiarity in reproduction. A single large egg is 

 formed in the ovary of the female, which, passing into 

 the oviduct, passes there through the larval stage, and 

 is finally dropped as a pupa or chrysalis. Unlike other 

 flies, therefore, these Hippoboscidce have no active 

 existence as maggots or caterpillars, reserving their 

 voracity for the perfect or imago stage, when they 

 make up diligently for lost time. Some of the family, 

 such as Hippobosca equina, the dreaded forest fly, and 

 Stenopteryx hirundinis, the parasite of the swallow, 

 are furnished with wings, and fly strongly ; others, like 

 Lipoptena cervi, which infests red deer, are hatched 

 with wings which they use until they have found a 

 host, when they bite them off or shed them, and devote 

 themselves exclusively to bloodsucking and reproduc- 

 tion. Others again, like Melophagus ovinus, the 

 common sheep-tick (which it may surprise some people 

 to be told is a real fly) are born wingless. Ticks are 

 troublesome and loathsome enough, but who shall 

 calculate the amount of irritation and suffering caused 

 to a swallow by the presence of two or three 

 Stenopterices among its feathers ? Why, in proportion 

 to the bird's size, each of these flies is as great as a 

 full-grown rabbit is to a man ! It is a kind of Nemesis, 

 to be sure, for swallows feed on flies; and here is a 

 fly, armour-coated, against which they are defenceless, 

 for it is too tough to be killed. These flies or kindred 

 species are known to infest various other birds, but 

 seem to be especially attracted to those of the swallow 

 family. The history of these parasites has been very 

 imperfectly elucidated hitherto, and offers a promising 



