Howard has called attention to some peculiarities in the pupation of Chalcididae.[[467]] Like the Cynipidae, they do not make a silken cocoon, but some of them that change to pupae inside the victims on which they were nourished have the power of forming oval cells in which to undergo their transformation, and they thus cause a peculiar inflation of the skin of their deceased victim, which after death still continues to serve as a protection to the destroyers. The statement made by Haliday, and repeated subsequently in various works, to the effect that Coryna spins a cocoon under the Aphis in which it has lived, is an error, the cocoon being really formed by Praon, a Braconid that is a parasite of the Aphis, and on which the Chalcid Pachycrepis (Coryna) lives as a hyperparasite. The pupae of some species differ from those of other Hymenoptera, in that the integument is hard, and the limbs are soldered to the body as in Lepidoptera. These forms pupate external to the victim.
Fritz Müller has recorded that the pupa of an unnamed species of Chalcid that attacks a Brazilian ant (Azteca instabilis Forel) is suspended on the wall of the cell the ant lives in by its posterior extremity, just like the chrysalis of a butterfly.
Notwithstanding the small size of Chalcididae, their remains have been detected in the tertiary strata of both Europe and North America.
Fam. IV. Ichneumonidae (Ichneumon-flies).
Wings with a well-developed series of nervures and cells; the space on the front wing separating the second posterior cell from the cubital cells is divided into two cells by a transverse veinlet. The abdomen is attached to the lower or posterior part of the median segment. Larvae parasitic in habits.
Fig. 360.—Lissonota setosa, ♀. Britain. Parasite of the goat-moth, etc. (After Ratzeburg.)
The Ichneumonidae form a family of enormous extent, containing nearly 6000 described species. The study of the family is but little advanced, owing to their parasitic habits and to this bewildering multiplicity in their specific forms. Most of the species, in the larval state, live inside the larvae of Lepidoptera, and they thus keep the myriads of caterpillars within bounds, the number of these destroyed by Ichneumons being prodigious. Some of the family are, however, external parasites, and some are known to attack Spiders and Insects of other Orders than Lepidoptera. Their antennae are not elbowed and are many-jointed, the joints being closely compacted, especially towards the extremity. This character readily distinguishes Ichneumonidae from the families we have previously considered. The ocelli are well developed even in the apterous forms, and are placed in a triangular position on the vertex. The pronotum is small in front; and extends backwards at the sides to the points of insertion of the front wings; it is fixed to the mesonotum. The wings (Fig. 367, A) have a more complex neuration than those of most of the other parasitic Hymenoptera, but are occasionally absent in one or both sexes of a species. The metathorax is very small, and the middle and hind legs are placed close together. The propodeum is very large, and is frequently covered with a highly-developed sculpture.
Fig. 361.—Anomalon circumflexum, larval development. (After Ratzeburg.) A, First instar; B, second instar; C, the larva in the third or encysted stage extracted from its cyst; D, the mature larva; E, pupa.