108 NATURAL HISTORY READER. 



their skin, the ants instantly carry it away, nor will they 

 let any dirt or rubbish remain among them or on them. 



8. But, the most amusing care of the ant is guarding 

 the aphides from the attacks of that little parasitic fly 

 whose operations Mr. Ilaliday has so well described. You 

 must have seen a sheep-dog run over the backs of a whole 

 flock of sheep, when closely crowded together, in order to 

 bring back some sinner that has gone astray ; so will the 

 ants, in the hot sunshine, run about over an establishment 

 of aphides, driving away the rascally parasite that is for- 

 ever hovering over to destroy them. 



9. The mode in which the ichneumon-flies operate on 

 the aphis is very remarkable. As may be inferred from 

 the size of the aphides, on which they are parasitic, they 

 are of very small dimensions, and one of these tiny creat- 

 ures, when standing on the back of an aphis which it is 

 about to wound, looks much like a rook perched on a 

 sheep's back. 



10. When the fatal egg has been introduced under the 

 skin of the aphis, the wounded insect, like the stricken 

 hart, separates itself from its fellows and passes to the 

 under-side of a leaf, and there fixes itself. Its body soon 

 begins to swell, and at last becomes quite globular and 

 horny, the change being caused by the death of the aphis 

 and the rapid growth of the parasite within it. The ich- 

 neumon passes rapidly through its changes, and in a short 

 time assumes the perfect form, always with its head next 

 the tail of its victim, pushes off the last two or three seg- 

 ments of the dead aphis, and makes its escape into the 

 world. The dead and empty skins of such hapless aphides 

 may be found plentifully toward the end of summer stick- 

 ing firmly to the leaf, and showing the round aperture 

 through which the destroying parasite has crept. 



11. Sometimes there is a sort of contest between the 

 aphis and the ichneumon-fly ; the former, however, hav- 



