150 
j. bront£ gatenby. 
Silvestri (2) has contributed some important papers on the 
subject, but these have appeared in an Italian agricultural 
journal only taken by a small number of the scientific 
libraries of this country. Considering the vast number of 
parasitic Hymenoptera which exist, and their diversity and 
remarkable instincts, a rich field, only now being explored, 
is opened to zoologists. But it is a field full of difficulties, 
for the Trichogrammids, to mention one group alone, are, as 
Perkins (4) , has said, among the smallest of known insects. 
In several other groups of parasitic Hymenoptera there are 
to be found numbers of forms whose life history and habits 
are of absorbing interest. The pure observer finds problems 
and instincts of wonderful diversity, and the embryologist is 
impressed with the remarkable adaptations for the modus 
vivendi which these forms follow. 
The remarkable oogenesis of some of these parasites has 
been the subject of some interesting papers by R. Hegner (3). 
The parasite, a part of whose embryology I have described 
in this paper, is a member of that important family the 
Chalcididae, a numerous and highly interesting assemblage of 
minute Hymenoptera. These insects are of great importance 
to the economic entomologist, because among them one finds 
forms which aid the agriculturist, and which often injure. 
Trichogramma might be said to aid. 
It is a pleasant duty to express my thanks to Mr. Goodrich 
for his kind interest in this work, and for advice and criticism, 
which has been of great value. 
The Host 1 (Donacia simplex, Fab.). 
Donacia simplex is quite common around Oxford in the 
early summer. Commander Walker informs me that he has 
occasionally taken this species at Oxford in winter. In the 
early summer one can always find the beetles on the water- 
1 Kindly identified by Mr. H. Britten, Assistant of the Hope Depart- 
ment, Oxford Museum. 
