Fig. 573.—Body of larva of Lithocolletis. swollen and filled with cocoons of Copidosoma, enlarged.
While those chalcidid larvæ which feed internally on their host, as a rule, transform into naked, more or less coarctate pupæ, Howard states that the larvæ of Copidosoma, Bothriothorax, Homalotylus, and perhaps others, which are much crowded within their host, cause a marked inflation of the body of the latter (Figs. 573, 574). The nature of this cocoon-like cell, and how it is produced, is unknown. “Its structure shows it not to be silk, nor yet the last larval skin of the parasite, and whether it is an adventitious tissue of the host-larva or a secretion of the parasite, or is explicable upon other grounds, I cannot say.”
The silken cocoon of an aphidiid ichneumon has been found by Miss Murtfeldt, and also by Dr. Riley, under a rose aphid in which it had lived, and referred by Howard to the genus Praon (Fig. 575).
Sanitary conditions observed by the honey-bee larva, and admission of air within the cocoon.—Cheshire has observed that after the larva of the honey-bee has spun its cocoon or silken lining of its cell, it observes the following means of preserving cleanliness. The food given to the larva, especially during the latter part of the growing period, contains much pollen, the cases of the grains of which consist of cellulose, which is indigestible.
Fig. 574.—Coccinellid larva infested by Homalotylus obscurus, enlarged.
Fig. 575.—Cocoon of Praon under the body of a dead Aphis, enlarged.—This and Figs. 573 and 574 after Howard, from Insect Life.
Fig. 576.—Pupation of Proctotrupes in the body of a larva of a beetle, representing a case mentioned by Dr. Sharp, where the parasites have pupated on the outside of the host, a pair of each attached to nearly each segment of the body of their host.—After Sharp.