120 [May, 1900. 



laid in or on the bodies of the wasps' grubs as soon as the latter are 

 of sufficient strength to maintain the forthcoming larvsB, since Dr. 

 Chapman informs me be has found the parasite in grubs occupying 

 the earliest-made layer of the wasps' nest. That they are, however, 

 confined to no particular part of the nest may be surmised, since M. 

 Roujet, of Dijon, tells us that in a couple of nests four or five 

 thousand cells were occupied by the cocoons of the parasite, besides 

 a great number of larvae ; and Curtis says that clusters of from two 

 to four cells together occupied various situations in the nest. The 

 Spliegophaga, having emerged from its egg, subsists upon the adipose 

 tissues of the wasp-grub, until the latter is full-fed, and, having sealed 

 down its operculum, has assumed the pupal state ; the parasite then 

 devours the remainder of its host from below, thus being shielded from 

 external attacks, first by the operculum, and secondly by the skin of 

 the dead pupa. Dr. Chapman says (almost in M. Eoujet's words) : 

 " On removing the silken dome, there is the pupal head of the wasp, 

 but pale and ghost-like." — " Like a lump of transparent jelly," says 

 Donisthorpe.' — " On examination the external colour is found to be 

 correct and undisturbed, but instead of opaque-whitish or yellow, with 

 dark eye-marks, the interior is full of a mere watery fluid ; further 

 examination shows the greater part of the wasp's thorax to be present 

 in a similar condition, and the remainder of the wasp to be represented 

 by some material (? dermal tissues) pressed up close against this."* 



The Laeva, according to Andre (p. 508 and pi. xxxiv, fig. 8) is somewhat 

 elongated, slightly curved, pointed at both ends, and rather swollen in the middle ; 

 soft, fleshy and white. The head, which is narrower than the anus, is also white, 

 and shows only somewhat indistinct traces of labrum and mandibles. It is blind 

 and apodous, only possessing some transverse fleshy ridges on the back of the ab- 

 dominal segments, evidently intended as a means of locomotion around its cell, 

 since they are true dorsal prolegs. The length of the adult larva is 9 — 10 mm., and 

 its diameter in the centre about 3 mm. 



Curtis noticed that about one-third of the wasp's cell was filled 

 with exuviae, and a similar case obtains in the cocoons in my possession 

 from which SphegopTiagce have emerged. Having devoured the grub, 

 the parasite fortified itself by building a very strong cocoon at the 

 bottom of the cell, obviously calculated to resist the attacks of the 

 wasps when they come to prepare the latter for a new occupant, and 

 this precaution would be especially necessary to those likely to pass 



* What interested Dr. Chapman most was the way in which the parasite cleared out the 

 tissues of the pupal head and replaced them with fl\iid, without in the slightest degree disturbing 

 the form of the parts. This fluid is, howerer, gradually absorbed by the parasite, and the grub'.s 

 skin becomes quite dry and of au inconsideral)le size ; the former probably goes to sustain its 

 often long pupal existence. 



