404 INSECT ARCHITECTURE. 



fit for boring through the hides of cattle. " When- 

 ever I have succeeded," he adds, " in seeing these 

 insects at work, they have usually shown that they 

 proceeded quite differently from what I had imagined; 

 but unfortunately I have never been able to see one 

 of them pierce the hide of a cov/ under my eyes."* 



Mr Bracey Clark, taking another view of the 

 matter, is decidedly of opinion that the fly does not 

 pierce the skin of cattle with its ovipositor at all, but 

 merely glues its eggs to the hairs, while the grubs, 

 when hatched, eat their way under the skin. If this 

 be the fact, as is not improbable, the three curved 

 pieces of the ovipositor, instead of acting, as Ri'aumur 

 imagined, like a centre-bit, will only serve to prevent 

 the eggs from falling till they are firmly glued to the 

 hair, the opening formed by the two shorter points 

 permitting this to be effected. This account of the 

 matter is rendered more plausible, from Reaumur's 

 statement that the deposition of the egg is not at- 

 tended by much pain, unless, as he adds, some 

 very sensible nervous fibres have been wounded. 

 According to this view, we must not estimate the 

 pain produced by the thickness of the instrument; 

 for the sting of a wasp or a bee, although very con- 

 siderably smaller than the ovipositor of the ox-fly, 

 causes a very pungent pain. It is, in the latter case, 

 the poison infused by the sting, rather than the 

 wound, which occasions the pain; and Vallisnieri is 

 of opinion that the ox-fly emits some acrid matter 

 along with her eggs, but there is no proof of this 

 beyond conjecture. 



It ought to be remarked, however, that cattle have 

 very thick hides, which are so far from being acutely 

 sensitive of pain, that in countries where they are put 

 to draw ploughs and v.aggons, they find a whip 



*= Mem. iv. 538. 



