PLANT-LICE. 



good indication of the presence of the psylla. . . . The 

 adult is about one-tenth inch long, of a reddish crimson 

 color with brownish-black markings, bronzy eyes and dark 

 wing-veins. . . . The egg is about one-eighteenth inch 

 long, hardly perceptible without a lens, and orange- 

 yellow in color. It is pear-shaped with the small end drawn 

 out into a long thread" (Sanderson). 



APHIDID^E 



t 



In his memoir on insects affecting park and woodland 

 trees Dr. Felt has a section which he entitles "The Battle 

 of the Weak or Interesting Facts about Aphids." The 

 title is striking and true. These creatures (Plate XXIV) 

 are called Plant-lice, Green Flies, Blight (from the damage 

 they do) and other things also. They are among the most 

 injurious, the most interesting, and the most puzzling of 

 insects. It would be difficult to improve on some of the 

 many general accounts of their life cycle; as Dr. Felt has 

 just been mentioned, his summary may be quoted : " 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 young hatch therefrom in some 

 cases at least at about the time the foliage begins to 

 develop and in other instances not till well toward mid- 

 summer, establish themselves at some favorable situation 

 and begin to draw nourishment from the unfolding tissues. 

 These young are all females and in the language of science 

 are known a,s 'stem mothers.' They usually begin to 

 produce young in a few days after hatching from the egg 

 and these are also females and in turn produce others. 

 This method of reproduction is what is known as agamic 

 or asexual and differs from the ordinary in that males have 

 no part in the process. A number of generations may be 

 produced in this way, the adults being wingless, and after 

 a time, usually at the end of a certain number of genera- 

 tions, winged females develop. These latter forsake the 

 original, usually by this time crowded, food-plant and 

 either fly to similar ones in the neighborhood or, as in the 

 case of some species, betake themselves to entirely different 



87 



