PARASITES OF GIPSY-MOTH CATERPILLARS. 189 
On the other hand, studies with the parasites of native insects 
have revealed the existence of what may be called accidental or 
incidental parasites. These may be important parasites of one 
insect and of no importance whatever in connection with another, 
nearly allied. Sometimes this is due to the fact that the one species 
of host may excite in the mother parasite the desire to oviposit, which 
is not excited by the other, and occasionally, as has more than once 
been observed, the pres- 
ence of the favored host 
in the immediate vicinity 
will induce the parasite 
to oviposit in another 
species which under 
otherwise identical cir- 
cumstances would be en- 
tirely ignored. At other 
times an insect may 
be acceptable to the 
mother parasite, but for 
some reason unaccept- 
able to her progeny, so that only a very few out of the many eggs 
which are deposited will go through to maturity, and the species will 
be of necessity considered as rare and unimportant. 
The fact that there are included in every list of the parasites of a 
given host a few species which are thus to be considered as incidental 
or accidental lends force to the contention that among the recorded 
parasites of the gipsy moth are several at least which come into the 
same category. Just which these are is not altogether plain at this 
time. 
Fig. 28.—A panteles solitarius: Adult female and cocoon. En- 
larged. (Original.) 
APANTELES SOLITARIUS Ratz. 
Cocoons of a solitary species of Apanteles (fig. 28) which attacks 
the very young to half-grown caterpillars of the gipsy moth through- 
out the greater part if not the whole of Europe have occasionally been 
received in shipments in which the caterpillars were not all in the last 
or next to the last stage. In those shipments which consisted of cater- 
pillars in the third, fourth, and fifth stages at the time of collection, 
the cocoons of this species have been the most common. In no 
instance has a sufficient number been received to make possible any- 
thing like a satisfactory colony of this species, and in all scarcely more 
than 100 have been received since the beginning of the work. 
The parasite undoubtedly attacks the first-stage caterpillars as 
well as those of the later stages up to the fourth at least, and per- 
haps the fifth. The host probably molts at least once, subsequent 
to attack, and remains alive after the emergence of the parasite larva, 
