ii 4 THE STUDY OF INSECTS 



grape-vines, drawing nourishment from the tender shoots and midribs of 

 the leaves during its young stages. 



Family Chermid^e 



The Jumping Plant-lice 



The jumping plant-lice are comparatively small insects; our more 

 common species measuring only from one-twelfth to one-sixth inch in 

 length, and it is rare that we find any twice that size. 

 When examined with a lens they appear like tiny cicadas 

 (Fig. 192). Their hind legs are formed for jumping; their 

 antennae are ten-jointed or rarely nine- or eleven-jointed. 

 They are very active creatures, jumping and taking flight 

 when disturbed. 



The Chermidse subsist entirely upon the juices of 

 plants, and some of them cause serious injuries. Many 

 species form galls; one of the larger of these infests the 

 leaves of hackberry. 



The most destructive member of this family in the 



-The near- United States is the pear-tree psyllia, Psyllia pyricola. 



^Psyiiia, greatly This is a minute species, measuring only one-twelfth inch 



in length to the tip of the folded wings (Fig. 192). 

 The eggs are laid early in the spring in the creases of the bark and in 

 the leaf-scars of the smaller branches. The young nymphs migrate to 

 the axils of the leaf petioles and the stems of the forming fruit; later 

 they spread to the under side of the leaves. They secrete large quan- 

 tities of honey-dew, upon which a blackish fungus grows. There are at 

 least four generations each year. Badly infested trees shed their leaves 

 and young fruit in midsummer. In some cases orchards have been so 

 badly injured by this pest that they have been cut down by their owners. 



Family Aphidid^j 

 The Plant-lice or Aphids 



The plant-lice or aphids are well-known insects; they infest nearly 

 all kinds of vegetation in all parts of the country. Our most common 

 examples are minute, soft-bodied, green insects, 

 with long legs and antenna?, which appear on various 

 plants in the house and in the field. Usually, at 

 least, in each species there are both winged and 

 wingless forms (Fig. 193). There are many species 

 of aphids, nearly all of which are of small size ; some 

 measure less than -^ of an inch in length; and our fig. i 93 . — a group of aphids. 

 largest species, only \ or \ of an inch. 



The body is usually more or less pear-shaped. The winged forms 

 have two pairs of delicate, transparent wings. These are furnished with 

 a few simple or branched veins. The first pair of wings is larger than the 

 other, and the two wings of each side are usually connected by a com- 

 pound hooklet or several hamuli. The beak is three-jointed, and varies 

 greatly in length; sometimes it is longer than the body. The compound 





