144 



EGGS 



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 



OlP^^ called the chorion ; (3) a layer of material 



added to the exterior of the egg from 

 glands, at or near the tinie 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 

 covered in whole or part with a complex 

 minute sculpture, of a symmetrical char- 

 acter, and in some cases this is very 

 highly developed, forming an ornamenta- 

 ; 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- 



FiG. 77. Upper or micro- 

 pylar aspect of egg of 

 Vanessa cardui. (After 

 Scudder. ) 



tion of much delicacy 



