54 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 
and did equally good service in preventing a further increase of the 
caterpillars. .Jt appeared somewhat earlier in the season, and killed 
only half-grown caterpillars. From the numerous old and empty co- 
coons in early summer it was plainly seen that a first brood had been 
quite numerous, and that from these cocoons mainly Apanteles had been 
bred, and not, as during the autumn, mostly secondary parasites. The 
white silky cocoon is formed almost under the middle of a half-.grown 
caterpillar, and is fastened securely to the object its host happened to 
rest upon, and but slightly to the host itself, which is readily carried to 
the ground by wind and rain, and can therefore only be found in posi- 
tion in the more sheltered places, such as cracks and fissures of the 
bark of trees. But one Apanteles is found in a caterpillar, so that each 
Fic. 25.—An Apanteles: a, female.fly; b, outline of head of larva in posi- 
tion to show the chitinized parts of the mouth, the mandibles not visible, be- 
ing withdrawn; c¢, one of its mandibles as seen within the head of amounted 
specimen; d, cocoon; e, joint of antenna—all enlarged; natural size of a and 
d in hair-line. 
white cocoon indicates, like a tombstone, the death of a victim. In some 
places, and notably upon the trunks of poplars, these cocoons were so 
numerous as to attract attention; it seemed as if the trunk had been 
sprinkled with whitewash. But notwithstanding such vast numbers, but 
two specimens of the architects of these neat cocoons were raised; all the 
rest had been parasitized by secondary parasites. It is barely possi- 
ble, however, that some specimens may hibernate in their cocoons, since 
numbers of them have as yet (December 20, 1886) not revealed any in- 
sects. The winged Apanteles leaves the cocoon by a perfectly round 
orifice in the front, by cutting off a little lid, which falls to the ground. 
Its parasites, however, leave by small holes cut through the sides. 
These secondary parasites were very common late in September and 
