FROTH-HOPPERS. APHID^E, OR PLANT-LICE. 189 



of which they subsist in all their stages ; and some of them are 

 employed by certain species of Ants, for the same purposes as the 

 Aphides ( 694 and 719). The Aphrophora spumaria is one of 



the best known British 

 species; its larva and 

 pupa, resembling the 

 perfect insect in almost 

 every respect save the 

 absence of wings, are 



FIG. 415. APHROPHORA SPUMARIA ; a, imago; found beneath a frothy 



exudation, especially 



upon willow-trees; and the exudation is sometimes so abun- 

 dant, from the large number of these animals, that persons 

 walking beneath are wetted by the continual dropping of the 

 fluid. A species nearly allied to this, inhabiting Madagascar, 

 discharges a clear instead of a frothy fluid ; and this in such 

 quantities, that it falls to the ground in the middle of the day, 

 when the heat is the greatest, in a continual shower. 



719. Section II. DIMERA. This section entirely consists of 

 minute insects ; of which the most remarkable family is that of 

 APHID.E, or Plant- Lice. These live in great numbers upon the 

 surface of plants of almost every description, and suck the 

 juices, by means of their proboscis, from the young shoots, 

 leaves, stems, and even roots. They greatly weaken its vigour, 

 and often distort young shoots and leaves ; some species cause 

 little gall-like excrescences by the irritation they produce. From 

 two horn-like processes at the posterior part of their bodies, a 

 saccharine secretion exudes, of which Ants are very fond ( 694); 

 and it is either this fluid dropped on the adjacent leaves, or the 

 extravasated sap flowing from the wounds made by the insects, 

 which is known under the name of honey- dew. In many of the 

 species of this family, a large proportion of the individuals never 

 acquire wings ; in which case the Pupa is not to be distinguished 

 from the Larva or Imago ; whilst at certain parts of the year, 

 other individuals of the same species, and of both sexes, acquire 

 wings. The wingless Aphides, which may be seen in the 

 spring and early summer, are all females capable of producing 



