INSECTS AlFECTIXG PARK AXD WOODLAND TREES 



241 



THE BATTLE OF THE WEAK 



OR 



INTERESTING FACTS ABOUT APHIDS 

 The Aphitlidae or plant lice comprise an exceedingl)- interesting group 

 and illustrate in a most admirable manner the means by which some of the 

 weaker forms of life are able to exist. The general characteristics of 

 aphids, or plant lice, are familiar to almost every person, since they are 

 exceedingly common on almost every plant, not excepting tliose grown in 

 houses. We all know that they are frail creatures, some with ami some 

 without wings, and so tender that it is extremely difficult to take one; up 

 without inflicting serious injury. These nearly helpless, practically defense- 

 less ft)rms are nevertheless represented in North America b_\- about 325 

 species, as given by Professor Hunter in a recent list. It is patent to all 

 that some of these species are occasionally enormously abundant, so that in 

 spite of their almost al)solute helplessness, there seems little danger of the 

 forms becoming extinct. 



Summarized life cycle. The life history of these interesting insects 

 may be briefly summarized as follows. Many of the species pass the winter 

 in what we know as the winter egg, which is usually deposited in crevices 

 of the bark or at the base of buds or branches, where it remains during the 

 winter. The \'oung hatch therefrom in some cases at least at about the 

 time the foliage begins to develop and in other instances not till well 

 toward midsummer, establish themselves at some favorable situation and 

 begin to draw nourishment trom the unfolding tissues. These young are 

 all females and in the language of science are known as " stem mothers." 

 They usually begin to produce young in a few days after hatching from 

 the tig'^ and these are also females and in turn produce others. 'I his 

 method of reproduction is what is known as agamic or asexual and difters 

 from the ordinary in that males have no part in the process. A number of 

 generations ma\' be produced in this wa\", the adults being wingless and 

 after a time, usuallv at the end of a certain numl)er of generations, winged 



