INDIRECT BENEFITS DERIVED FROM INSECTS. 265 



largest ; and the individuals of one species clothe them- 

 selves, like Hercules, with the spoils of their hapless 

 victims. 



Next in importance to these come the aphidivorous 

 flies (many species of Sijrphlda;)^ whose grubs are armed 

 with a singular mandible, furnished like a trident with 

 three points, with which they transfix their prey. They 

 may often be seen laid at their ease under a leaf or upon 

 a twig, environed by such hosts of Aphides, that they 

 can devour hundreds without changing their station ; 

 and their silly helpless prey, who are provided with no 

 means of defence, so far from thinking of escaping, fre- 

 quently walk over the back of their enemy, and put 

 themselves in his way. When disposed to feed, he fixes 

 himself by his tail, and, being blind, gropes about on 

 every side, as the Cyclops did for Ulysses and his com- 

 panions, till he touches one, which he immediately trans- 

 fixes with his trident, elevates into the air, that he may 

 not be disturbed by its struggles, and soon devours. 

 The havoc which these grubs make amongst the Aphides 

 is astonishing. It was but last week that I observed the 

 top of every young shoot of the currant-trees in my gar- 

 den curled up by myriads of these insects. On examin- 

 ing them this day, not an individual remained ; but be- 

 neath each leaf are three or four full-fed larvae of aphi- 

 divorous flies, surrounded with heaps of the skins of the 

 slain, the trophies of their successful warfare; and the 

 young shoots, whose progress had been entirely checked 

 by the abstraction of sap, are again expanding vigor- 

 ously. 



But even these serviceable insects must yield the palm 

 to the lady-bird or lady-cow {Coccindla), the favourite 



