THE INSECT WORLD. 



147 



small, slender insects with the wing-covers narrow and slightly 

 thicker than the broad hind wings, which are the only effective 

 organs of flight. The thorax is broad and square, the head 

 usually short and very broad, in most cases somewhat crescent- 

 shaped, with prominent eyes occupying a large part of the sides. 

 If we examine the insects on the under side it appears as if the 

 beak or rostrum came out from the breast between the front legs, 

 so much is the head curved under. The antennae are very short 

 and bristle-like ; the legs are well developed, the hind pair espe- 

 cially being very long and powerful, set with spines on the tibiae, 



F"iG. 108. 



Development of a Jassid, Agallia sanguinolenla.—a, larva; h, pupa ; c, adult ; also head 

 of same from below. 



somewhat as in the grasshoppers, and like them the insects are 

 powerful leapers. This they are in all stages, but as adults they 

 are also ready fliers, and hence difficult to capture. Many of 

 them are common and, feeding on cultivated plants, are injurious. 

 As in other families, there is considerable difference in the life 

 history of the species ; but of most of those of economic impor- 

 tance it may be said that they pass the winter in the adult stage, 

 hiding in all sorts of rubbish or in crevices, wherever they find 

 opportunity. Some time in spring they leave their winter quar- 

 ters, attack the plants upon which they feed, and lay eggs. The 

 number of hibernating individuals is usually not very great, but 

 they lay a large number of eggs, and the young and future broods 

 become troublesome. One of the best- known species is that 



