74 



INSECTS. 



host, and reaching the ground bury themselves, and remain concealed until 

 they emerge as perfect insects from the pupal stage. The three species above 

 mentioned serve as types of the life-histories of the entire family, which contains 

 in addition a large number of genera and species infesting various kinds of 

 animals. Even man himself is not exempt from their attacks, and all kinds of 

 domestic cattle and beasts of burden, such as reindeer, camels, and elephants, are 



liable to be infested with them. 

 Two notices of the occurrence of 

 larvae in human beings were pub- 

 lished by John Howship in 1833. 

 In both cases the larvae, named 

 (Estrus humanus, were extracted 

 from tumours, the sufferer in 

 one case being a soldier in 

 Surinam, and in the other a 

 carpenter in Columbia. In 

 addition to the mammals men- 

 tioned, others, such as hares, 

 rabbits, mice, and voles, often 

 suffer from these parasites. Their 

 larvae have also been met with 

 in birds and frogs. Schneider, 



for instance, states that two larvae much resembling those of Hypoderma were 

 obtained from under the skin of the head of a young sparrow, where they had 

 produced two large hard tumours, and Krefft has given descriptions of specimens 

 belonging to the genus Batrachomyia that were found living parasitically upon 

 Australian frogs. The larvae were situated between the skin and the flesh behind 

 the drum of the ear, and could be squeezed out through apertures in the skin. 



LIFE-HISTORY OP SHEEP BOT-FLY. 



a, Adult fly ; b, Larva from tipper side ; c, Pupa from under 

 side (all enlarged). 



FOREST-FLIES, Family HIPPOBOSCID^E. 



This family brings us to the second section (Pupipara) of the Cyclorrohapha, 

 all the members of which are no less remarkable amongst flies for the strangeness 

 of their appearance than for their method of development. They are all short and 

 flat, with longish and powerful legs which enable them to run with great speed ; 

 some of them being entirely wingless, with the mouth-parts much reduced ; but in 

 the mode of their development they are absolutely unique in the entire order. In 

 the first place only a single young one at a time is produced, and this, instead of 

 being laid in the egg-stage, remains within the mother, nourished at her 

 expense by means analogous to those which obtain in the higher mammals. When 

 born, the young is either actually a pupa, or immediately assumes the pupa-state, 

 being motionless, without segmentation, and entirely protected by a horny shell, 

 which imparts to it the appearance of the seed of a vetch. The members of this 

 section, which are mostly parasitic on birds or mammals, are referable to three 

 families. Of these, the forest-flies are represented by several genera, all the members 

 of which are parasitic upon mammals or birds, and are frequently spoken of as 



