2 Hewitt, Cytological Aspect of Parthenogenesis in Insects. 



very little at present, by the careful study of par- 

 thenogenesis in all its aspects. 



Parthenogenesis occurs in the majority of the orders 

 of Insects, and in this group we can recognise all the 

 types of the phenomenon, as they are known from a 

 study of the general or somatic changes which take place. 



To obviate the necessity of explaining at length in 

 each case the type of parthenogenesis which occurs in 

 that particular family which we may be considering, it 

 will be convenient if they are arranged in the following 

 tabular form, which is a slight modification of Henne- 

 guy's (45) classification : — 



1. TycliopartJienogencsis (Henneguy). 



This includes those cases of Parthenogenesis which 

 are accidental and of exceptional occurrence, 

 such as are found in the Lepidoptera and 

 Coleoptera. 



2. HomopLirthenogenesis (Henneguy). 



Under this term which replaces Hatschek's term 

 Isoparthenogenesis, all cases of normal 

 Parthenogenesis are included. They may be 

 further divided into 



{a) Thelyotoky. 



Parthenogenesis in which only females are produced. 

 This occurs in some species of Tenthredinidae. 



{b) Arrhenotoky. 



Parthenogenesis in which only males are produced. 

 This occurs in the Hymenoptera Sociales and 

 some species of Tenthredinidae. (The workers 

 of some Ants, Bees, and Wasps may produce 

 parthenogenetic eggs, though this is only 

 occasional, but in all cases they produce males). 



