in the Body ofVlialdna BSmbi/x Cdja, 253 



running and jumping about in all directions, but were col- 

 lected in the greatest number on that side of the cage nearest 

 to the light. Not having leisure to attend at the moment to the 

 securing, killing, and setting them, I closed the door of the 

 cage, and left the house for some hours : judge of my astonish- 

 ment and mortification, on returning, at not being able to dis- 

 cover a single individual. I shook out the whole of the moss, 

 fragment by fragment, but in vain, nor have I since been able 

 to guess what became of them. 1 however observed that 

 many of the pupae had very small and perfectly circular holes, 

 through which the little hymenopterous insects must have 

 made their egress ; the holes made in the pupae by the flies 

 being much larger, and jagged at the edges. The following 

 morning I was gratified by finding a new, but much less 

 abundant, supply of the Hymenoptera ; I instantly secured 

 some of them, and they appear to belong to the genus 

 Pteromalus Dal. 627. Curfis's Guide, I now proceeded to 

 open with the point of a penknife the remaining pupae of the 

 ^ombyx; the perforated ones contained nothing but the 

 exuviae or pupa cases of the Pteromali ; but among the others, 

 which were hard and stiff, and apparently dead, 1 found one 

 quite filled with the coarctate pupae of a Miusca. On apply- 

 ing the point of my knife to these, I found some contained 

 flies [Muscae], which, thus prematurely liberated, never came 

 to perfection ; but by far the majority of these flies or ikfuscae 

 were filled with Pteromali in the various stages of larva, 

 pupa, and imago. The Muscas, although imperfect, I ascer- 

 tained on comparison to be the ikfusca larvarum of Linne ; 

 a specific name, however, to which I suspect more than one 

 true species is referable. 



Here then was a parasite on a parasite, the Musca being 

 evidently the original parasite of the ^ombyx, and the Pte- 

 romalus as evidently parasitical on the ikfusca. A very inter- 

 esting question arises from this discovery. How could the 

 parent Pteromalus introduce its eggs into the larva of the 

 Musca; that larva being completely immersed in the interior 

 of one of our most hairy caterpillars, a situation apparently 

 so secure ? I fear we shall long want a practical solution of 

 the problem ; in the mean time, we must content ourselves 

 with a theoretical one. 



It is well known to all those who have paid much atten- 

 tion to the rearing of lepidopterous insects from the larva, 

 that they are subject to two distinct tribes of parasites, /ch- 

 neumones and ik/uscae. The females of the /chneumones are 

 furnished with a long sharply pointed oviduct, for the express 

 purpose of piercing the skin of the destined victim of their 



