THE FALL WEB-WORM. 



255 



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 position 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 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 possible, however, that some specimens may 

 hibernate in their cocoons, since numbers of them have as yet (December 20, 1886) 



Fig. 94. — 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, 

 being withdrawn ; c, one of its mandibles are seen within the head of a 

 mounted specimen; d, cocoon; e, joint of antenna — all enlarged: natural 

 size of a and d in hair-line. After Riley. 



not revealed any insects. The winged Apanteles leaves the cocoon by a perfectly 

 round oritice iu 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 early in October, and busily en- 

 gaged in inserting their ovipositors through the tough cocoon into their victim 

 within. It seems as if the cocoons formed early in the season were on an average a 

 little .smaller than those formed later. 



The cocoons of this Apanteles are of a uniform white color, but exceptioually a dis- 

 tinctly yellowish cocoon is found. From these yellow cocoons nothing has so far 

 been bred, but since, as we have elsewhere shown,* the color of the cocoon may vary 

 in the same species, it is probable that the variation here referred to is not specific. 



Not quite one-half of 1 per cent, produced parasites of various kinds. 



Limneria pallipes Provancher. — In addition to the two Hymenopterous parasites 

 treated of, a third one has been very numerous, and has done much good in reducing 

 the numbers of caterpillars. This, an Ichneumonid and a much larger insect, does 

 not form an exposed cocoon like that of the other parasites described. Yet a little 



Notes on North American Microgasters, p. 7 (author's edition). 



