416 THE PHYTOPHTHIRIA. 



colony takes up its residence. Others, principally 

 belonging to the genus Lachnus, in which the rostrum 

 is very long, live in crevices of the bark upon the 

 trunks of trees. Others, again, forming the genus 

 Rhizobius and its allies, live under the earth and 

 attack the roots of plants ; these never acquire wings. 



On each side of the extremity of the abdomen in 

 these insects, we find a small tubular process, from 

 which a sweet juice exudes, frequently in such abun- 

 dance as to drop from the insects upon the leaves of 

 the plants and even to the ground, where it is well 

 known under the name of Honey-dew. The nature 

 of this fluid, which often forces itself upon our notice 

 under these circumstances, was long a matter of 

 dispute, as it was supposed to be a morbid exudation 

 from the plants themselves. Some Hymenopterous 

 insects, especially the Ants, are very fond of this fluid, 

 and may constantly be found in search of it upon the 

 trees and shrubs frequented by Aphides. 



If we examine a colony of Aphides during the 

 summer, we generally find it to consist both of winged 

 and wingless individuals. Some of the latter, which 

 are of smaller size, are the young, but many of them 

 are perfectly mature and capable of reproduction. 

 But the mode in which this reproduction is effected, 

 is most singular, and, in fact, considering the extent 

 to which it goes, we can point to no similar instance 

 in the animal kingdom. The individuals found in 

 summer upon plants are all capable of producing 

 living young, which, after a few days of rapid growth, 

 during which they change their skins two or three 

 times, are again capable of giving birth to a living 

 progeny, although no male insect has made its appear- 

 ance, and this process goes on from the first appear- 



