58 REMARKS ON THE ATTACKING OF PUP.E. 



general organization, but possessing the number of segments — thirteen — wliich 

 is typical of the class of Insects." 



Edinlurgh, Febnuiry 2nd., 1852. 



EEMARKS ON THE 



ATTACKING OF PUP^ BY ICHNEUMON FLIES. 



« 



BY JOHN GRAY, ESQ. 



In No. 9 of "The Naturalist/' we observe a query from a correspondent, 

 whether the pupae of insects were pierced by the Ichneumon, and what proof 

 could be adduced in support of any such assertion? 



This has, we believe, been long a matter of dispute amongst entomologists; 

 and till recently we were ourselves often puzzled about it. It is well enough 

 known that caterpillars, when preyed upon by Ichneumons, in some cases, 

 really undergo the chrysalis change, before the creatures kill them. This is 

 not unfrequently the case when a caterpillar has been attacked when nearly 

 full grown; the larvae of the Ichneumon, by a very wonderful degree of instinct, 

 refraining from injuring any of the vital organs, till they themselves are nearly 

 full fed. Hence the fact of Ichneumons emerging from a chrysalis where their 

 presence had not been previously suspec^ted; having, indeed, been fed within 

 the body of the caterpillar for a short time, and then completing their 

 metamorphoses after it assumed the pupa state. That sujh is the case is now 

 pretty well ascertained from the recorded experience of several naturalists; but 

 here any further elucidation of the question, which we propose to deal with, 

 stops; at least we are not aware of any practical observations having yet 

 been made. It is also, we believe, well known, and this must be borne in 

 mind, that the pupae of caterpillars so attacked invariably die not long after 

 their change into the chrysalis state. It is evident that they must do so, for 

 as soon as the parasitic larvae have devoured the internal organs, life must 

 become extinct. From these observations it is quite clear that any facts bearing 

 on the question at issue, can only be gleaned from watching the progress of 

 the development of the chrysalis, aftei' it has been collected in the pupa state. 



About two years ago we collected a considerable number of the pupae of 

 moths, by digging around the roots of various shrubs and hedges; one of these 

 we found exposed above the surface of the ground, where it had evidently 

 been turned up some time before by the scratching of barn-door fowls at a 

 farm-house, in the immediate vicinity. On taking it up we at first suspected 

 that it might be injured, but were soon reassured by the lively wriggling of 

 the abdominal segments, and its otherwise healthy appearance. We placed it 

 in our breeding cage, and on examining it some days afterwards, we found it 

 still apparently healthy. As no moth made its appearance, however, during 

 the whole summer, we then criticised it a third time, but with a very diifcrent 

 result, for on taking it up, we found the pupa case had become quite thin 



