126 The Life-History of Insects 



Larval Reproduction. — But though the repro- 

 ductive function is eminently characteristic of the 

 perfect state, the pupa of a Midge has been observed 

 to lay eggs, and it occasionally happens that the 

 ovaries become mature during larval life, so that eggs 

 are produced which, without fertilisation, develop 

 within the body of the grub (8o), young larvae 

 being born in an active condition of a larval mother. 

 This very remarkable form of virgin reproduction 

 (known as pedogenesis) has been observed in certain 

 Gall-midges {Cecidomyia). A yet more astonishing 

 form of premature generation has lately been noticed 

 in a minute insect (Chalcid) parasitic in small cater- 

 pillars. The egg of the chalcid (laid in the egg of 

 the moth) gives rise after segmentation not to a single 

 embryo, but, by a process of division, to fifty or 

 a hundred embryos, which develop as their host, 

 the caterpillar, develops. The reproductive function, 

 normally confined to the adult, but thrown back in 

 the Gall-midges occasionally to the developed larva, 

 is in the case of this tiny Chalcid performed by the 

 young embryo (8l). 



Our short survey of the life-history of insects has 

 shown us the endless variety that can be traced in 

 the methods of their growth from the egg to the 

 perfect form. In the course of the descriptions, 

 attention has occasionally been drawn to what seem 

 plain indications of the steps by which some of these 

 various methods of growth have been brought about. 

 In the simpler and more primitive insects, the young 

 closely resemble the adults ; while among insects 

 which pass through a metamorphosis, those with a 

 passive pupal stage are more highly developed than 

 those which move and feed throughout their lives. 

 We may gather from these facts that metamorphosis 



