108 OUTLINES OF ENTOMOLOGY. 



bodied and gregarious, and most numerous in the wingless forms. 

 The eyes are usually quite large and of a dark color, and the antennae 

 of many species long and thread-like; the beak is two-jointed, and in 

 some cases as long or longer than the body ; legs, in the leaf-feeding 

 species, rather long and slender, but in the root-feeding and gall-inhab- 

 iting forms short and stout; wings thin and transparent, with dark 

 veins on the anterior margin. Near the tip of the abdomen, on the 

 back, many species have a pair of little tubes through which exudes a 

 sweet fluid, sometimes in such quantities as to thickly besprinkle the 

 plants infested. This is then termed "honey dew," although the genu- 

 ine "honey dew" is an excretion from the leaves of certain plants 

 during dry, hot weather. Ants, as is well known, are extremely fond 

 of "aphis nectar," and induce the insects to yield it in large quantities 

 by caressing them with their antenna?, for which reason they are called 

 the "ants' cows." Other species of aphides excrete from a part or the 

 whole of the surface of the body a wbitish powder or " bloom," or 

 numerous filaments of fine, cottony matter, in which they become com- 

 pletely enveloped. The reproductive processes of aphides are very 

 complicated and remarkable, and have been the subject of much care- 

 ful study and experiment. Our knowledge in regard to them may be 

 briefly summarized as follows : At certain seasons of the year — usually 

 late in summer or early autumn — individuals of both sexes are pro- 

 duced, and the females lay eggs, which in some species hatch immedi- 

 ately, in others remain dormant over winter. The sexed aphides were 

 formerly supposed to be^ the winged form, but later discovery shows 

 that there is not necessarily any connection between the possession of 

 wings and of true sexual organs, the wings being simply an adaptation 

 for migration from one locality or plant to another. The form hatching 

 from the egg is denominated the "stem mother," and in the course of a 

 few days begins a peculiar process of reproduction, called partheno- 

 genesis or agamis reproduction, bringing forth her young alive and in 

 very rapid succession. This process has been likened to the multipli- 

 cation of certain kinds of plants by slipping and budding. The off- 

 spring of the "stem mother " begin, in their turn, to produce vivipa- 

 rously in the course of a few days, and in this way the multiplication of 

 individuals proceeds at a most extraordinary rate. Fortunately for the 

 safety of vegetation, plant lice have a variety of natural enemies. They 

 may also be destroyed by alkaline applications, tobacco smoke or in- 

 fusion, or kerosene emulsions. Poisons such as Paris green or London 

 purple do not have much effect upon them, as they do not eat leaves, 

 but puncture them and extract the sap from beneath the cuticle. 



