395 



Leaf of the Currant-bush, bulged out by the Aphis ribil. 



which we have seen, occurs on the leaves of the elm, 

 and is caused by the Aphis ulmi. The edge of an 

 elm-leaf inhabited by those aphides is rolled up in 

 an elegant convoluted form, very much like a spiral 

 shell ; and in the embowered chamber thus formed, 

 the insects are secure from rain, wind, and, partially, 

 from the depredations of carnivorous insects. One 

 of their greatest enemies, the lady-bird (Coccinella), 

 seldom ventures, as we have remarked, into concealed 

 corners, except in cold weather, and contrives to 

 find food enough among the aphides whteh feed 

 openly and unprotected, such as the zebra aphides of 

 the alder (Aphides sambuci). The grubs, however, 

 of the lady-bird, and also those of the aphidivorous 

 flies (Syrp/ii), may be found prying into the most 

 secret recesses of a leaf to prey upon the inhabitants, 



