PARTHENOGENESIS. 



form of the head behind the eyes give the best specific 

 characters. 



The Cynipina are chiefly known from the Palse- 

 arctic and Nearctic zoological regions. Very pro- 

 bably they are found wherever oaks and roses abound. 

 They are abundant in the United States of America, 

 are known from Mexico (Gynips, Aulax, Synergus),B,nd 

 from Northern India. One genus (Eschatocerus, Mayr) 

 is recorded from the Banda Oriental, where it forms 

 galls on acacia. The genus Bhodophilus, Mayr, comes 

 from the Cape of Good Hope, galliug Rhus lucidum. 

 A few species are common to Europe and America, 

 e. g. Bhodites rosx, Aulax glechomse. 



Gynips is practically absent from the northern parts 

 of Europe, but is prevalent in the centre and south of 

 Europe. It is rare in the United States. 



Parthenogenesis and Alternation of Generation 



Until the time of Hartig the many anomalous 

 features in connection with the natural history of the 

 gall insects received but scant if any attention. 

 Hartig in 1843* became aware of the fact that cer- 

 tain species appeared to have no males, and in the 

 course of his experiments, bred no less than 9-10,000 

 examples of Dryophanta foli out of 28,000 galls, every 

 one being a female. Hartig surmised, from his ana- 

 tomical examination of the insects, that they were 

 hermaphrodite ; but his observations on this point 

 were speedily disproved by von Siebold.f 



A survey of the subject at that time led to the 

 generalisation that those species which appear in 

 spring or early summer were bisexual, while those 

 whose galls appeared in the autumn were without 

 exception agamic. On the supposition that this was 

 so, it followed that the spring gall-flies must lay eggs 



* Germ. Zeit., iii, 398. 

 f L. c, iv, 362-388. 



