CHAPTER 8 



Reproduction 



Reproduction in most insects is bisexual; the egg cell liberated by 

 the female will develop only after fusion with the spermatozoal cell 

 set free by the male. The physiology of reproduction deals with the 

 arrangements for the separation and ripening of these male and 

 female gametes, and with the mechanisms by which they are brought 

 together. The reproductive system consists of paired sexual glands, 

 the testes of the male and the ovaries of the female, paired gonoducts 

 of mesodermal origin into which the sexual products are discharged, 

 and a median duct lined with cuticle, derived by invagination from 

 the ventral body-wall, forming the vagina in the female and the 

 ejaculatory duct in the male. 



Male and female reproductive systems 



The testis of the male is made up of a series of tubular follicles of 

 varying number and arrangement. Each follicle contains a succession 

 of zones in which the sex cells are in different stages of development. 

 Each 'spermatogonium' arising in the 'germarium' at the apex of the 

 follicle divides repeatedly to form a cyst filled with 'spermatocytes' 

 covered with a mantle of somatic cells. The spermatocytes divide to 

 form 'prespermatids' and then 'spermatids' which, finally, in the lower 

 extremity of the follicle, become transformed into the elongated and 

 flagellated spermatozoa. The spermatozoa are usually discharged 

 through an intromittent penis or 'aedeagus' in adherent bundles or 

 packets mixed with the secretion of a pair of accessory glands. 



The ovary of the female is likewise composed of a series of tubular 

 follicles or 'ovarioles'. In these the oocytes arising in the germarium 

 do not multiply repeatedly as do the germ cells in the male but each 

 becomes enormously enlarged to form the egg cell or ovum. The 

 oocytes become enclosed in a mantle of 'follicular cells' ; they are 



