ANT COMMUNITIES 



appears soon after the 1 leaves expand, and is found 

 throughout the season. I have seen American for- 

 est trees attacked by aphids, from which the honey- 

 dew was flung out in such quantities that it sounded like 

 the patter of rain-drops as it fell upon the dry leaves and 

 grass beneath the infested branches. The whole surface 

 of the ground underneath was covered with the liquid 

 sweet, and thousands of ants, bees, wasps, and various 

 other insects had assembled to the forest feast. 



The reproductive processes of aphids are extremely 

 complicated and remarkable, and have been the subject 

 of much careful study and experiment. At certain sea- 

 sons of the year, usually late in the summer or early 

 autumn, individuals of both sexes are produced, and the 

 females lay eggs which in some species hatch immedi- 

 ately. In others they remain over the winter. Sexed 

 aphids were formerly supposed to be the winged form, 

 but late discoveries show that there is not necessarily 

 any connection between the wings and the true sexual 

 organs, the wings being simply an adaptation for migra- 

 tion from one plant to another. 



The form hatching from the egg is known as "the 

 stem-mother," and in the course of a few days begins 

 the peculiar process of reproduction known as parthe- 

 nogenesis, or agamic reproduction, bringing forth her 

 young alive and in rapid succession. This process has 

 been likened to the multiplication of certain kinds of 

 plants by slipping and budding. The offspring of the 

 stem-mother begin to produce viviparously in the course 

 of a few days, and in this way the multiplication of in- 

 dividuals proceeds at a most extraordinary rate, extend- 

 ing to several generations. 



In the pear-tree psylla, for example, the hibernating 



246 



