THE GRASSHOPPER 



345 



at least for a number of generations, in two Lepidoptera and one beetle, 

 in some coccus insects and aphids, and in certain saw-flies and gall- 

 wasps. It occurs casually in the silk-moth, in some grouse, locusts, and 

 several other Lepidoptera, seasonally in aphids, in larval life in some 

 flies [Miastor ( ), Chironomus ( )] 



and partially or "voluntarily" when the queen-bee lays eggs which be- 

 come drones. 



PAEDOGENESIS 



Among certain tiny flies hardly one millimeter in length and known 

 as midges (Fig. 226) there are pupae which produce eggs without fertili- 



Fig. 226. Order Hymenoptera. D. 



A, gall-fly, Rhodiles rosoe, female. B, galls produced by a bug. (A, from the 

 Cambridge Natural History; B, from Davenport, after Kerner). 



C. Order Diptera. Hessian fly, Cecidomyia destructor (one of the midges). 

 a, larva. 6, pupa. (From Davenport, after Standard Natural History). 



D. Young paedogenetic larvae of Miastorca genus of the family Cecidomyiidae 

 in the body of the mother larva. (After Pagenstecher). 



zation. The larvae of the gall-gnat, the related members of this family, 

 and related Chironomidae likewise do this so that here we have a case 

 of a granddaughter commencing to grow and develop not only without 

 fertilization, but before the mother and grandmother themselves become 

 full-fledged imagoes or adult insects. 



The larvae in such cases are hatched within the parent larva and 

 "in some cases escape by the rupture of the body." 



Such development of one, two, or three generations within the im- 

 mature animal is called paedogenesis ( ). 



POLYEMBRYONY 



In 1904 P. Marchal described an interesting observation. He found 



that in two small parasitic Hymenoptera ( ), a 



Chalcid ( ) Encyrtus ( ) 

 which lay eggs in the developing eggs of the small moth Hyponomeuta 



( ) and a Proctotrypid ( ) 



Polygnotus which infests a gall-midge Cecidomyid ( ) 



