245 
from a single host, which bore 13 eggs, four parasites. In addition 
to these Tachinas also 6 Ichneumon flies were bred from cater- 
pillars with 7achina-eggs. In all the 150 caterpillars bore 767 
eggs, and the number of bred flies was 144, so that only about. 
a fonrth of the parasites succeeded in accomplishing their develop- 
ment. The size of the flies was of course very variable, differing 
between 5 mm. and 13 mm.; in the cases where several flies 
emerged from the same host, their size was not equally reduced, 
one or two of them not differing in size from that of flies which 
had developed solitary, the remainder being undersized.  Allmost 
all of the maggots pupated within the skin of the dead hosts. 
Tachina impotens Rond. 
The larva is parasitic in the caterpillars of Orgyia antigqva L., 
which were found on a thorn-hedge in the neighbourhood of Copen- 
hagen. The eggs were deposited only on the fullgrown caterpillars 
and with few exceptions on the underside of the body, in the 
furrows between the thoracic segments or between the head and 
the first segment. The fly was not common, and the caterpillars 
were nearly all provided with only a single egg each — one only 
being found with two. Consequent to the maturity of the cater- 
pillars a great number of them pupated before the parasite had 
penetrated into their body and thus escaped being killed by the 
maggots; owing to this fact many of them, into which the Tachina 
maggots had penetrated, pupated, before they were killed. Of 34 
caterpillars 21 pupated before the Tachina-eggs were mature, and 
13 after the penetration; of the lastnamed 9 pupated before they 
were killed and only 4 were killed by the parasites before the 
pupation. The fullgrown Tachina-maggot leaves the remains before 
pupating and pupates in the hosts cocoon. The infested caterpillars 
were collected in the months of August—September, and all the 
flies emerged in October. 
