4 Mr. J. Blackwall on a Species of Ichneumon. 



but merely spun a few irregular lines to which they attached 

 themselves. 



It is a fact deserving of notice, that immature spiders in- 

 fested with the larva of this Ichneumon do not change their 

 skins. Were it not for this admirable provision of Providence, 

 the larva, cast off with the integuments in the act of moult- 

 ing, would inevitably perish, and the important purpose which 

 its remarkable ceconomy is so evidently intended to subserve, 

 namely, the keeping of these deadly enemies of the insect 

 tribes within due limits, would fail to be accomplished. 



Various circumstances concur to render it probable that 

 this species of Ichneumon deposits its eggs on spiders in the 

 autumn, attaching one only to the abdomen of each individual. 



Messrs. Kirby and Spence, in treating on the diseases of 

 insects in the fourth volume of their { Introduction to Entomo- 

 logy,' have given a brief account of observations made by De 

 Geer on the larva of a small Ichneumon discovered on a young 

 spider, whose ceconomy is similar to that of the parasite which 

 has engaged my attention*. 



Being desirous of ascertaining whether these insects were 

 of the same species or not, and having no opportunity of con- 

 sulting De Geer's celebrated work, I availed myself of the 

 assistance of Mr. Peter Barrow of Manchester, who obligingly 

 transcribed all that the Swedish entomologist had published 

 on the subject, and transmitted it to me in Wales. 



On perusing the description of the female Ichneumon bred 

 from the larva which formed the subject of his investigations f, 

 I found that it presented several decided points of difference 

 in colour from the species observed by me, from which it may 

 be distinguished at once by the two longitudinal yellowish 

 lines on its thorax. 



It scarcely admits of a doubt, that the whitish oval object 

 noticed by Baron Walckenaer on a specimen of Linyphia 

 montanaX, which seems to have induced no small degree of 

 surprise and perplexity in the mind of that accomplished 

 arachnologist, was the parasitic larva of a small species of 

 Ichneumon^. 



» Letter 44. p. 221. 



*f* MSmoires pour servir a l'Histoire des Insectes, torn. ii. p. 866. 



j Histoire Naturelle des Insectes Apteres, torn. i. p. 176. 



[§ In a letter recently received from the author he thus writes : " The 

 insect is not uncommon in this neighbourhood (Oakland); indeed, the Ich- 

 neumonidce abound throughout the district. Two other species belonging 

 to this family, which deposit their eggs in those of spiders, have come under 

 my observation ; one is very small and black ; the other is small, though 

 larger than the former: and the female, which is apterous, is of an orange- 

 red colour, with a black head, and a zone of the same hue encircling the ab- 

 domen." — Ed.] 



