27 
llth, the egg of the parasite having been laid too late to interfere with 
the development of the adult Orgyia, or perhaps the already greatly 
toughened skin- of the pupa was not penetrated by the ovipositor of the 
Chalcis. 
Owing to the failure to rear parasites from pupa? or larva? in which 
the adults were observed to oviposit, the length of the life round can 
only be surmised. It is unquestionably, however, very short. The 
tussock-moth caterpillars were transforming to pupa? rather rapidly 
at the end of the first week in September, and, as just noticed, the 
Chalcis flies were abundant at this time, and were actively engaged in 
ovipositing The first adult of the parasite was reared on September 17 
from a discolored pupa found September 13. The second one issued on 
the 18th from a discolored pupa taken on the 17th, and the third on the 
19th from a pupa taken on the 4th. The longest period under observa- 
tion in the fall of 1895 occurred in the case of certain cocoons taken on 
August 23, from which the majority of the Chalcis flies issued from the 
19th to the 25th September, and from which a very few belated indi- 
viduals issued as late as October 19. The probabilities are that at this 
time of the year the entire life round of the parasite occupies on an 
average from three to four weeks. A little later it is naturally length- 
ened. From the mass of cocoons taken September 10 the last Chalcis 
issued October 4. 
In issuing from the Orgyia pupa this Chalcis invariably gnaws a hole 
through the dorsum of the first and second thoracic segments. This 
hole is usually a little to one side of the median line. 
It is an easy matter to recognize the Orgyia pnpae which have been 
parasitized by this species. Not only is the large round hole near the 
head of the pupa characteristic of Chalcis ovata — that is to say, char- 
acteristic among the parasites of the tussock moth — but if the chrysa- 
lis be broken open the pupal exuvium of the Chalcis will always be 
found, and this is in itself so characteristic as to be recognized at a 
glance. The sheaths of the large hind femora and those of the corre- 
sponding tibia 1 and tarsi projecting straight out at nearly right angles 
from the femora distinguish this exuvium from that of any of the other 
parasites. It is well shown at fig. 12 e. Very many of these para- 
sitized pupa? of the Orgyia were examined. Never more than a single 
pupal exuvium of the Chalcis was found. If more than a single speci- 
men develops in a single Orgyia pupa, it has not been observed. This 
is rather strange, for it is seldom that the entire contents of the body of 
the pupa are devoured by this parasite, and in many female pupa? from 
which an adult Chalcis had emerged fully one half of the eggs were 
undisturbed and sound. 
No instances have been recorded in which this insect seemed to be 
hyperparasitic, but there was in the collection a swollen larval skin of 
an Orgyia caterpillar apparently parasitized by some other insect, from 
which had issued from the anterior ventral segment a specimen of this 
Chalcis, according to the label. The specimen was carefully dissected 
