346 



General Biology 



There are a few insects which give birth to living young. Such are 

 the parthenogenetic summer aphids, a few flies, the little bee parasites, 

 Strepsiptera, a few beetles and cockroaches. But by far the greater por- 

 tion lay eggs, the young then developing from these. 



When eggs develop which have not been fertilized, birth is said to 

 be by parthenogenesis ( ). This occurs normally, 



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 

 become drones. 



PAEDOGENESIS 



Among certain tiny flies, hardly one millimeter in length and known 

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



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 f Order Diptera. Hession fly, Cecidomyia destructor (one of the midges). 

 a, larva, b, 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.) 



fertilization. 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 ( ), 



