234 
A short resume. 
Biologieal notes on some Danish species of Synergus. 
I. Andricus Sieboldii and A. Rhizomae. Parasitic on these 
II. 
lives Synergus incrassatus. When the galls are infested 
with the eggs of Synergus their development is stopped 
at the stage when they begin to become conical and 
most often they remain concealed under the bark, but 
occasionally, when the gall is of unusual size or when 
several galls are placed in a row the bark may burst 
after all; in the case last mentioned a number of low - 
dome shaped galls are seen. 
In these deformed galls are in the winter found a number 
of from one to twelve pupae of the parasite. In the in- 
dividual gall, however, is only found one sex, either male 
or female. The reason of this is, that the species is de- 
cidedly proterandrous, the males being developed 8—14 
days before the females. If they were now mixed in the 
same gall, the males in emerging and in leaving the 
gall would disturb the female pupae, which at this time 
would be still quite soft and immature. 
On Andricus trilineatus the parasites are Synergus hey- 
aneus Htg., S. rugulosus Htg. and Megastigmus dorsalis F. 
While the host is developing and leaving the galls in 
September and producing the galls of the agamous ge- 
neration: Andricus radicis, the parasites hibernate in the 
galls. The reason of this is, that they cannot live 
parasitic on the large A. radieis and that at this season 
there are no galls of the proper host, on which to de- 
posit their eggs. They must therefore remain in the 
galls till April or May, when they leave the galls and 
lay their eggs on the young galls of Andricus trilineatus, 
produced on young oak branches by Andricus radicis, 
which at this time is emerged. In other words, this 
species of Synergus skips the agamous generation of 
its host. 
