DEVELOPMENT l6l 



to fasten the eggs to appropriate objects, such as food plant-. 

 the skin of other insects, the hairs of mammals, etc. ; it may 

 form a pedicel, or stalk, for the egg, as in Chrysopa ( I ; ig. 

 209) ; may surround the eggs as a gelatinous envelope, as in 

 caddis flies, dragon flies, etc. ; or may form a capsule enclosing 

 the eggs, as in the cockroach. 



The number of eggs laid by one female differs greatly in 

 different species and varies considerably in different individ- 

 uals of the same species. Some of the fossorial wasps and 

 bees lay only a dozen or so and some grasshoppers two or three 

 dozen, while a queen honey bee may lay a million. Two 

 females of the beetle Priomis laticollis had, respectively, 332 

 and 597 eggs in the abdomen (Mann). A. A. Girault gives 

 the following numbers of eggs per female, from an examina- 

 tion of twenty egg-masses of each species : 



Maximum. Minimum. Average. 



Thyridopteryx ephemeraformis 1076 753 941 



Clisiocampa americana 466 313 375-5 



Chionaspis furfura 84 33 66.5 



Hatching. Many larvae, caterpillars for example, simply 

 eat their way out of the egg-shell. Some maggots rupture 

 the shell by contortions of the body. Some larvae have spe- 

 cial organs for opening the shell ; thus the grub of the Colo- 

 rado potato beetle has three pairs of hatching spines on its 

 body (Wheeler) and the larval flea has on its head a tempo- 

 rary knife-like egg-opener (Packard). The process of hatch- 

 ing varies greatly according to the species, but has received 

 very little attention. 



Larva. Although larvae, generally speaking, differ from 

 one another much less than their imagines do, they are easily 

 referable to their orders and usually present specific differ- 

 ences. Larvae that display individual adaptive characters of 

 a positive kind (Lepidoptera, for example) are easy to place. 

 but larv.T with negative adaptive characters (many Diptera 

 and Hymenoptera) are often hard to identify. 



