Dl \ I I M|'\!l 



nun. in width; I lie <>v;il eggs of the trtrnfn,i moth, mi the other : 

 :nin. 



'I'h. .-II. or i //<>rion. secreted around tin- ovum l>y edit of the 



ovarian follicle, may he smooth hut i- u < ulpl ured. fre<|in-nfly 



with riders which, as in lepidopten>u~ M the 



shell. The ornamentation ol" t he egg shell is often ex(juisile|y b 

 though the particular patterns dis|)layed are probably of no use, being 

 incidentally produced as Impressions from the cells which secrete the 

 chorion. Variations of form, si/e and pattern are frefjuent in eggs 

 of the same species, as appear- in Fig. 211. 



Always the chorion is penetrated l>y one or more openings, constitut- 

 ing the micro pylc, for the entrance of spermatozoa. 



A- a rule, the eggs when laid are accompanied by a fluid of some sort, 

 which is secreted usually by a cement gland or glands, opening into the 

 vagina. This fluid commonly serves to fasten the eggs to appropriate 

 objects, such as food plants, the skin of other insects, the hairs of 

 mammals, etc.; it may form a pedicel, or stalk, for the egg, as in 

 Chrysopa (Fig. 212); may surround the eggs as a gelatinous envelope, 

 as in caddis tlies, 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 individuals 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 Prionus laticollis had, respectively, 

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

 lowing numbers of eggs per female, from an examination of twenty egg- 

 masses of each species: 



MAXIMUM MINIMUM AVERAGE 



Thyridofrteryx ephemer&formis (bagworm) 1649 465 941 



M'dacosoma americana (tent caterpillar) 466 313 375-5 



Chi onas pis fur f ura (scurfy scale) 84 33 66.5 



Hatching. -Many larvae, caterpillars for example, simply eat their 

 out of the egg-shell. Some maggots rupture the shell by contor- 

 tions of the body. Some larvae have special organs for opening the 

 shell; thus the grub of the Colorado potato beetle has three pairs of 

 hatching spines on its body (Wheeler) and the larval flea has on its head 

 a temporary knife-like egg-opener (Packard). The process of hatching 

 > greatly according to the species, but has received very little 

 attention. 



