1 44 EGGS CHAP. 



produced one at a time, and are born in the pupal stage of their 

 development, the earlier larval state being undergone in the 

 body of the parent : thus a single large egg is laid, which is 

 really a pupa. 



The eggs are usually of rather large size in comparison with 

 the parent, and are produced in numbers varying according to 

 the species from a few 15 or even less in some fossorial 

 Hymenoptera to many thousands in the social Insects : some- 

 where between 50 and 100 may perhaps be taken as an 

 average number for one female to produce. The whole number 

 is frequently deposited with rapidity, and the parent then dies 

 at once. Some of the migratory locusts are known to deposit 

 batches of eggs after considerable intervals of time and change 

 of locality. The social Insects present extraordinary anomalies 

 as to the production of the eggs and the prolongation of the life 

 of the female parent, who is in such cases called a queen. 



The living matter contained in the egg of an Insect is 

 protected by three external coats : (1) a delicate interior oolemm ; 

 (2) a stronger, usually shell-like, covering 

 called the chorioii ; (3) a layer of material 

 added to the exterior of the egg from 

 glands, at or near the time when it is 

 deposited, and of very various character, 

 sometimes forming a coat on each egg 

 and sometimes a common covering or 

 capsule for a number of eggs. The egg- 

 shell proper, or chorion, is frequently 

 FIG. 77. -Upper or micro- covered in whole or part with a complex 

 pylar aspect of egg of minute sculpture, of a symmetrical char- 



Vanessa cardui. (After j , i 



Scudder ) acter, and in some cases this is very 



highly developed, forming an ornamenta- 

 tion of much delicacy ; hence some Insects' eggs are objects of 

 admirable appearance, though the microscope is of course necessary 

 'to reveal their charms. One of the families of butterflies, the 

 Lycaenidae, is remarkable for the complex forms displayed by the 

 ornamentation of the chorion (see Fig. 78, B). 



The egg-shell at one pole of the egg is perforated by one or 

 more minute orifices for the admission to the interior of the 

 spermatozoon, and it is the rule that the shell hereabouts is 

 symmetrically sculptured (see Fig. 77), even when it is unorna- 



