SCAVENGERS KEPT BY SPIDERS. 213 



with a speckled brown spongy-looking mass, which, on close 

 examination, is seen to consist of tiny bits of withered leaves, 

 overgrown by a very small white fungus ; and should the 

 nest be disturbed, the ants are evidently most anxious to 

 carry every morsel of this " food " under shelter, and when 

 they migrate invariably take it with them. It is also certain 

 that they do not eat the leaves themselves, so one can only 

 conclude that they need them for the purposes of cultivation. 

 The refuse-particles, when exhausted as manure, are stowed 

 away in deserted chambers, and serve as food for the grubs 

 of beetles. 



Rose-beetle grubs are often found in the nest of the 

 wood-ant (Fig. 42), probably for the sake of the chips of 

 wood, fir-needles, &c., which they need 

 for their cocoons. 



Nor are ants the only creatures 

 which keep scavengers. Some of the 

 larger spiders allow certain small species 

 to live on the outskirts of their large, 



strong webs, and to. feed on such minute 



, . . Fig. 42. WORKER 



insects as are beneath their own notice, WOOD-ANT. 



and would otherwise not only be wasted, 

 but become a nuisance by choking up the web. Mr. Darwin 

 tells us that the booby and noddy of the desolate St. Paul's 

 Rocks, where nothing in the shape of a plant, not even a 

 lichen, grows, have their attendant scavengers, in the shape 

 of a woodlouse, a feather-feeding moth, and a beetle. 



Among the most important scavengers we must reckon 

 the flies, since there are very few which do not, at one time 

 or other of their existence, feed on decaying matter, animal 



