THE GAD-FLIES. 377 



usually express their emotions of fear or anger, rush 

 wildly about the fields, bellowing loudly, and always 

 seeking to get into the water, as that position appears 

 to give them some protection from their tormentor. 



The Gad-fly of the Sheep (Cephalemyia Ovis) adopts 

 another mode of attack : its larva resides in the maxil- 

 lary and frontal sinuses of the sheep, and the fly accord- 

 ingly deposits its eggs in the nostrils of those animals, 

 from which the larvae creep up through the nose, and 

 thus find their way to their destination. The sheep 

 exhibit a full consciousness of the mischievous inten- 

 tions of their winged attendant, and as soon as she 

 makes her appearance, use every effort to prevent her 

 from effecting her purpose, shaking their heads vio- 

 lently and running about, or occasionally collecting 

 into a ring, with their heads close together and their 

 noses applied to the ground. The larvae of a nearly 

 allied species, supposed to be the C. picta, have occa- 

 sionally been found in the fallow deer, inhabiting a 

 pair of cavities which exist in that animal close to 

 the root of the tongue. 



The well-known Bots which often occur in such 

 abundance in the intestines of the horse and ass, 

 are the larvae of another species of this group, the 

 Gasterophilus Equi. In providing for the introduction 

 of her progeny into this rather difficult situation, the 

 Bot-fly exhibits a great amount of ingenuity, for she 

 even renders the horse himself instrumental in con- 

 veying his parasites to their destination. She deposits 

 her eggs upon the hairs of particular parts of his 

 body, always selecting such situations as are easily 

 reached by his tongue, so that in licking himself, the 

 moisture and warmth of his tongue soon produce the 

 evolution of the larvae, which then adhere to the 



