1914| A Study of Dryophanta Erinacet. i 
the abdominal angle of the larva of Dryophanta erinacei. Here 
it often hatches. The larva breaks the shell near the base of 
the neck, (Fig. 37, Pl. IV.), and emerges, proceeding to attack 
the host in the abdominal region. If the Cynipid larva has 
just molted it is destroyed at once. If on the other hand, it 
escapes the attacks of the parasites during this period, they will 
live together until the next molt occurs, when the host is almost 
invariably killed and eaten. Only on rare occasions have the 
host and parasite been found living together in the same cavity 
until both have reached 1mm. in length. 
If two parasitic larve of the same or different species are 
found in one cavity in the early stages, the stronger alone 
survives, for | never have observed more than one adult emerge 
from a single cavity. Since no Chalcid eggs are found in the 
cavities inhabited by the inquilines, we may conclude that the 
Chalcids are parasitic primarily on Dryophanta erinacei, and 
secondarily on one another. 
The larva of Eurytoma studiosa and Eurytoma auriceps 
develop rapidly, and from the twenty-fourth of July to the first 
of August adults emerge, thus giving a summer brood. No 
adults of Decatoma flava emerge in the summer or autumn. 
After the parasites have destroyed the host, it is questionable 
whether they feed on the plant tissue, since the lining of the 
cavity they inhabit turns brown, becoming hard and brittle 
much earlier than is the case with the cavities occupied by. 
Dryophanta erinacei. 
It is impossible to determine absolutely the extent of para- 
sitism in these galls, yet we gain some idea from the following. 
During four weeks 1050 galls were examined, which showed 
sixty per cent of parasitism not including the internal parasites 
which had not emerged from the maker. 
Inquilines, their relation to Dryophanta erinacet, to the parasites, 
and to each other during the development of the gall. 
The relation of the inquilines of this gall both to the host 
and to the parasites is very interesting, since they are present 
not only as guests, but also as parasites. The parasitic charac- 
ter of certain species of Synergus has already been pointed out 
by Moller and Mann, but nowhere have I found any record of 
their singular action as observed in this gall. Synergus erinacei 
is not only parasitic on Dryophanta erinacei, and the parasites 
