2 8 The Scottish Naturalist. 



of Generations or Dimorphism occur in European Cynipidae?" 

 in which he argued theoretically against the existence of such an 

 alternation of generations ; but since then he has admitted that 

 he "attached too much importance to mere negative observa- 

 tions;" and is "very glad to say that I have this spring made 

 some observations on Neurotenis lenticidaris which confirm those 

 of Dr Adler" (Entom. Month. Mag., XV. p. 13, June 1878). 



In 'The Canadian Entomologist' for May 1878 (Vol. X. p. 

 85), Dr H. Hagen has reviewed the whole subject; and as the 

 magazine in which his paper appears is probably not seen by a 

 majority of our readers, we will reprint most of the article. We 

 may mention that several other entomologists have been suc- 

 cessful in repeating Dr Adler's experiments. 



Dr Hagen writes as follows : — 



" The natural history of the interesting gall-insects is still some- 

 what mysterious. A large number of observations have been made 

 here and in Europe by prominent entomologists ; nevertheless, 

 a careful study of the most detailed papers always gives the 

 impression that something is still wanting to explain the various 

 facts related by the authors. Among the Hymenopterous gall- 

 insects important progress was made in the discovery, by the late 

 B. Walsh, of the dimorphism of C. q. spongifica and C. q. acicii/ata, 

 the latter one a parthenogenetic species. But even here new 

 observations are wanted to fill some gaps in the history of those 

 species. Mr W. F. Basset, of Waterbury, Conn., draws my 

 attention to the fact that in a letter in the Proc. Entom. Soc. 

 Lond., April 1873, p. xv, he 'did state most emphatically his 

 belief that all one-gendered gall-flies were the alternate of a two- 

 gendered brood from galls of a different form.' 



" Two papers by Dr Adler, from Schleswig — ' Contributions 

 to the Natural History of the Cynipidae,' and ' On the Ovi- 

 positor and on Oviposition of Cynipidce,' in ' Berlin Entom. 

 Zeitschr.,' vol. xxi., 1877, Dec. — which have just arrived here, 

 are prominently remarkable. I believe the way so long sought 

 for is found, to understand the complicated relations not only of 

 the Hymenopterous gall-insects, but probably of all other gall- 

 insects, and perhaps, also, of some other insects not gall-pro- 

 ducing. These papers are equally remarkable botli vby the 

 manner of the experiments, the judicious conclusions drawn 

 from them, and the clear and plain description of what he has 

 observed. Dr Adler has raised the species through several 

 years. In Cynipidae the raising is less difficult, as the eggs are 



