38 



wliicli condition tlioy are but little clLauged ; tlioso, however, 

 Avhicli are to become wiuged insects have the rudiments of 

 ■wings. 



Manj^ persons think -when they see a certain haziness in the 

 atmosphere, which tliey call blight, that it is caused by immense 

 multitudes of these insects, urging, in proof of their theory, 

 the very sudden appearance at times of niAa'iads of Aphides. No 

 doubt plants which were a few days before, as far as could be 

 seen, qiute free from them, may be found covered with tliese 

 insects, but on examination nearly all the Aphides will be 

 found to be wingless, and cjuite incapable of flight. The real 

 causes of plauts being so suddenly covered liy these insects are 

 that a great number of eggs hatch about the same time, and 

 that reproduction is effected in a wonderfully rapid manner. 



During the summer nearly all the Aphides are viviparous, 

 wingless females ; very few males are to be found. About six 

 daj-s, and sometimes in less time, after they are hatched from 

 the eggs, these females, having paired, give birth to young, who 

 in about the same time become the parents of another genera- 

 tion. A viviparous female of the common Eose Aphis, Siphon- 

 oi^hora rospo, which I was watching under a microscope, gave 

 birth to two yonng ones within half an hour. This is, however, 

 I believe, an uniisuall}' rapid rate. Mr. Buckton, in his work 

 on Aphides, says he has known eight to be bom from one 

 female in six hours, and has calculated that the living progeny 

 of a Rose Aphis, supposing each Aphis lived 20 days and pro- 

 duced 20 young, at the eud of 100 days would be 3,200,000, and 

 at the end of 200 days 10,240,000,000,000 a number we cannot 

 in any way realize. Professor Huxlej' has stated that if all the 

 members of the tenth generation alone survived, and assuming 

 that an Aphis weighs 1 -100th of a grain, they, the tenth genera- 

 tion, wovild weigh more than 500 millions of stout men, or more 

 than the population of China. When we consider these figui-es 

 we can understand why our plants are sometimes so rapidly 

 covered with these insects, and why our hoj^s and other crops at 

 times suffer so severely from their attacks ; and we should be 

 indeed thankful that owing to tlieir natural enemies, which are 

 very numerous, we are not more troubled with these pests. 

 Another very curious fact about Aphides is that a female having 

 paired, not only is she rendered fertile, but also her jn'Ogeny for 

 many succeeding generations. 



The Aphides, whether in the pei-fect or immature states, live on 

 the juices of plants, Avhich they obtain with the assistance of a 

 proboscis, or rostrum, ^\•hich is composed of three joints. When 

 not in use it lies on the breast or underside of the insect, between 

 its legs. In some species it is larger than the insect, and what 

 at first sight appears to be a tail, on closer examination turns 



