Walker : On Ichneumonidje. 



79 



NotHng daunted, tlie insect returned to the charge, and having 

 selected a suitable spot, pierced the miserable caterpillar, which gave a 

 series of violent twitches as the remorseless insect expelled the fatal 

 germs. Several times in succession was the operation repeated, and 

 sometimes the ovipositor was allowed to remain in the wound for 

 several seconds. The parasite then flew off, brushed and cleaned 

 itself, and seemed thoroughly satisfied with its work. Every female 

 ichneumon that I placed in the box did likewise, until the unfortunate 

 caja was perfectly riddled with holes. 



Though it will be necessary to return separately to each stage of an 

 ichneumon's existence, it will perhaps be as well to trace the life-history 

 of this species, as far as my personal observations will permit. The 

 grub, when ready to change into the pupal state, is -|- of an inch long, 

 and is reddish coloured. Unlike some ichneumons of other species, 

 they do not spin their cocoons gregariously, but affix them in a pro- 

 miscuous manner, very seldom to the hairs of the larva. Forty-seven 

 grubs of the parasite emerged from one larva, and when I dissected the 

 victim, twenty-two more were discovered within. Another specimen, 

 which shared the fate of its predecessor, was, when opened, found to 

 be full of a putrid fluid, thick, and of a dirty brown colour ; even the 

 viscera were devoured. 



The imagines made their appearance about eighteen or twenty days 

 after the entrance of their larvae into the pupal state. ^ A few words 

 regarding the eggs of these interesting insects. So far, I have con- 

 fined my remarks to those IcJineiunomdce, which oviposit within the 

 body of the larva. We now arrive at another class, those that deposit 

 their ova on the outside of the larva. In this division, under which 

 may be classed the genus OpJiion, each egg is attached to a peduncle or 

 foot-stalk, which, in its turn, is firmly secured to the body of the cater- 

 pillar, so firmly indeed, that it is not in any way affected by the re- 

 peated moultings of the larva. When the eggs hatch, the young larvae 

 do not desert the empty egg shells, but attach themselves within them 

 by their anal extremity, and by the aid of their mandibles, rob the 

 caterpillar of its vital fluids.® I will just notice two other methods 

 of oviposition, in which the ovum of the ichneumon is neither de- 

 posited within nor without the caterpiUer, but in one class is secured 

 to the egg of the moth, and in the other actually placed within it.® 

 There are very few insects, indeed, absolutely safe from the attacks of 



See my communication in the Young Naturalist," Vol. 1, p. 30L 

 ® Westw. Class of insects. Vol. 2. p, 145. 

 © Ibid. Vol. 2. p. 144. 



