192 INSECTS INJURIOUS TO VEGETATION. 



the attacks of other insects, and carry them about in their mouths 

 to change their pasture ; and that they pay particular attention to 

 the eggs of the Hce, frequently moistening them with their tongues, 

 and in fine weather bringing them to the surface of the nest to 

 give them the advantage of the sun. On the other hand, the sweet 

 fluid supplied in abundance by these lice forms the chief nutri- 

 ment both of the ants and their young, which is sufficient to ac- 

 count for their sohcitude and care for thejr valuable herds. 



The peach-tree suffers very much from the attacks of plant- 

 lice, which live under the leaves, causing them by their punctures 

 to become thickened, to curl or form hollows beneath, and cor- 

 responding crispy and ^reddish swellings above, and finally to per- 

 ish and drop off prematurely. Whether our insect is the same as 

 the European Aphis of the peach-tree [Jlphis Persicce of Sulzer) 

 I cannot determine, for the want of a proper description of the 

 latter. The depredations of these lice is one of the causes, if not 

 the only cause of the peculiar malady affecting the peach-tree in 

 the early part of summer, and called the blight. 



The injuries occasioned by plant-lice are much greater than 

 would at first be expected from the small size and extreme weak- 

 ness of the insects ; but these make up by their numbers what they 

 want in strength individually, and thus become formidable enemies 

 to vegetation. By their punctures, and the quantity of sap which 

 they draw from the leaves, the functions of these important organs 

 are deranged or interrupted, the food of the plant, which is there 

 elaborated to nourish the stem and mature the fruit, is withdrawn, 

 before it can reach its proper destination, or is contaminated and 

 left in a state unfitted to supply the wants of vegetation. Plants 

 are differently afTected by these insects. Some wither and cease 

 to grow, their leaves and stems put on a sickly appearance, and 

 soon die from exhaustion. Others, though not killed, are greatly 

 impeded in their growth, and their tender parts, which are attack- 

 ed, become stunted, curled, or warped. The punctures of these 

 lice seem to poison some plants, and affect others in a most sin- 

 gular manner, producing warts or swellings, which are sometimes 

 feolid and sometimes hollow, and contain in their interior a swarm 

 of lice, the descendants of a single individual, whose punctures 

 were the original cause of the tumor. I have seen reddish tumors 



