INSECTS 



381 



in the immature condition for an extraordinary length of time 

 (see p. 225). These insects possess a strong ovipositor, and in 

 this case it is used to bore a 

 hole in a twig within which the 

 eggs are laid. 



In most of the Scale-Insects 

 iyCoccidcB) the wingless females 

 are covered by a sort of shield 

 (fig. 901), formed by the har- 

 dening- of a fluid which exudes 

 from the body, and in the con- 

 struction of which the cast skins 

 of the insect are also worked 

 up. The shape and texture of 

 these "scales" varies greatly 

 according to the species. In 

 most cases the female remains 

 in the same spot, with her sharp 

 beak driven into the plant on 

 which she lives, for the purpose 

 of sucking its juices. She lays 

 numerous eggs, often dying and 

 shrivelling up immediately af- 

 terwards, and these hatch out 

 under the shelter of her body. The nymphs which emerge lead 

 an active life for a time, but ultimately fix themselves by means 

 of their beaks. Those which become 

 females assume the adult shape by a 

 series of gradual changes, but the males 

 pass through a quiescent pupal stage, 

 ultimately becoming, at least in some 

 cases, active insects in which the fore- 

 wings are present, while the hind-wings 

 are reduced to vestiges, and the mouth- 

 parts entirely absent. 



Aphides or Plant- Lice {Aphides, fig-. 



-^ \ ^ ' & Fig. 901.— Apple Scale-Insect {Mytil- 



Q02), often known as "grreen fly", are <"/«;>'"«<'""»!, enlarged, a, Maie. 



. ' . ^ . , . r •!• • B, Female, c, Nymph. 



mmute msects 01 astomshmg lertility, m 



which the life-history is complex. During the warm part of the 



year, when food is abundant, there is a continuous succession of 



Fig. goo. —Home of Mole-Cricket {Gryllotalpa ca>J!/>cs- 

 tris), in vertical section, a, Eggs in incubating chamber; 

 b, young Cricket in "nursery"; r, adult. 



