86 THE APHIDES OF GUERNSEY. 



accorded. In the second place the general naturalist has 

 found much to engage his earnest attention, whether he 

 regards the varied life history of the different species of 

 Aphides, their curious habitations, the injuries they inflict on 

 vegetation, or the defences they make against the host of 

 insect foes which attack them on all sides — attacks which 

 keep within hmits an extraordinary fecundity, which other- 

 wise might bring famine into the districts they infest. A 

 single insect may be the mother of many billions of young 

 during her life-time." 



Professor Huxley makes the following curious calculation : 

 " Assuming that an Aphis weighs as little as one-thousandth 

 of a grain, and it requires a man to be very stout to weigh more 

 than two million grains, he shows that the tenth brood of 

 Aphides alone, without adding the products of all the 

 generations which precede the tenth, if all the members 

 survive the perils to which they are exposed, contains more 

 ponderable substance than 5U0 millions of stout men ; that is 

 more than the whole population of China." 



Fortunately for us the Aphides have many enemies 

 among the insect tribes. Numerous minute species belonging 

 to the Hi/mcnojitera exert their powerful influence in keeping- 

 down this redundance of Aphis life. Their huwa; are footless 

 grubs, which develop from eggs laid by the Avinged females, 

 generally singly, but sometimes five or more within the bodies 

 of the Aphides. These grubs live on the food assimilated by 

 the Aphides, and do not, until the last moment, attack their 

 vital organs. 



One species, Allo/wia erythroccpliala^ almost saves the 

 water-lily from destruction, by its attacks on Hhopalosiphui/i 

 717/mphcece, which sometimes kills the plants over large surfaces 

 of the Thames and other sheets of water. Mr. Smee stated 

 that hundreds of acres of this beautiful plant were destroyed 

 by this Aphis at Hampton Court. 



Many of the larger Htjmenojitouf belonging to the family 

 of the Crobonidce provision their cells with A])hides to provide 

 food for their young. 



The different species of beetles popularly known as 

 lady-birds are chief among the enemies and checks to 

 the Aphides, their food consisting almost exclusively of these 

 insects. Whilst feeding, the Aphis is seized by the lady-bird 

 near the back and the contents quickly sucked out of the 

 abdomen, one minute being required for the process. Mr. 

 Buckton observes that " we may express some hope, in 

 sympathy with the Aphis, that the automatic theory of 



