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NATURAL HISTORY. 



Account of the Ga(I.Fli/,from various 

 Authors. 



Jl he genus oestrus or gad-fly is 

 remarkable, like that of ichneu- 

 mon, for the singular residence of 

 its larvae, viz. beneath the skin, or 

 in different parts of the bodies of 

 quadrupeds. 



The principal European species 

 is the oestrus bovis or ox gad-fly. 

 This is about the size of a common 

 bee, and is of a pale yellowish brown 

 colour, with the thorax marked by 

 four longitudinal dusky streaks, and 

 the abdomen by a black bar across 

 the middle, the tip being covered 

 with tawney or orange-coloured 

 hairs: the wings are pale brown, 

 and unspotted. 



The female of this species, when 

 ready to deposit her eggs, fastens 

 on the back of a heifer or cow, and 

 piercing the skin witli the tube, si- 

 tuatcd at the tip of the abdomen, 

 deposits an egg in the puncture : she 

 then proceeds to another spot at 

 some distance from the former, re- 

 peating the same operation, atinter- 

 tals, on many parts of the animal's 

 back. This operation is not per- 

 formed without severe pain to the 

 animal on which it is practised ; and 

 it is for this rcq,sun that c»ttlc arc 



observed to be seized with such vio- 

 lent horror, when apprehensive of 

 the approaches of the female oes- 

 trus ; flying with uncontrollable ra- 

 pidity, and endeavouring to escape 

 their tormentor by taking refuge in 

 the nearest pond ; it being observed 

 that this insect rarely attacks cattly 

 when standing in water. 



In the punctures of the skin thus 

 formed by the gad-fly, the several 

 eggs hatch, and the larvae, by their 

 motion and suction, cause so many 

 small swellings or abscesses beneath, 

 the skin, which growing gradually 

 larger, become externally visible, 

 exhibiting so many tubercles an inch 

 or more in diameter, with an open- 

 ing at the top of each, through 

 which may be observed the larva, 

 imbedded in a purulent fluid: its 

 appearance is that of an oval mag- 

 got, of a yellowish white colour 

 while young, but growing gradually 

 darker as it advances in age, till at 

 the time of its full growth it is en, 

 tircly brown. It is chiefly in the 

 months of August and September 

 that the eggs are laid, and the larvaj 

 remain through the cnsuir)g winter 

 and (ill the latter part of the next 

 June, before they are ready to un- 

 dergo their change into chrysalis. 

 At this pcsiod they forco themselves 



out 



