4548 Insects. 



watch the course of events last autumn, but, though the ichneumons 

 were neither entirely absent nor yet inactive, the proportion of their 

 victims to those which escaped seemed very small indeed. During 

 this season, however, the number of "fly blown" caterpillars must, I 

 conceive, have been ten times that of 1853, even although the aggregate 

 amount of both sound and unsound may have been less; from which 

 circumstance I am disposed to anticipate the great mitigation, if not 

 the total cessation, of the plague in 1855. 



Among countless nests of ichneumons already changed to the 

 chrysalis state, I searched long before I could discover an example of 

 the little maggots in the act of emerging from the body of the cater- 

 pillar, but eventually succeeded very fully. By that time the cater- 

 pillar is in a torpid condition (but not dead, since it moves if 

 touched), remaining quite still while the parasites gradually extricate 

 themselves with a wriggling motion, sometimes in such a quantity 

 that it is impossible to count, without removing, them. I have seen 

 a mass which I should estimate at two dozen at least. Their next 

 change must occur very rapidly, for in one instance I examined a 

 brood, of which only one was distinctly visible, and that was busily 

 engaged in spinning the silky web wherein it was to be enveloped. 

 On my return, in about twenty minutes, I looked again, when the 

 little creature had completely concealed itself. A very large propor- 

 tion of the ichneumon-cases have now for some time been empty, but 

 what may be the general rule with regard to the perfect insect coming 

 forth must be left to entomologists. The flies I have seen were very 

 small. 



In the first volume of the ' Zoologist' (Zool. 326), I have related some 

 illustrations I had noticed of the prevalence and sudden disappear- 

 ance of certain insects, which disappearance, in one case, I was able 

 to trace to its probable cause. The phenomena now described are of 

 the same class, being among the innumerable proofs we possess of the 

 care wherewith a wise and beneficent Providence maintains " the ba- 

 lance of power" in its creation; and showing that, although vermin 

 of various degrees and kinds are occasionally sent in vast multitudes 

 for our chastisement or our trial, provision is also mercifully made for 

 the alleviation and final removal of the infliction. 



In the course of the observations detailed above I remarked a few 

 particulars, which may be appended to this account. Among the 

 victims of the ichneumon flies I have not known one green cater- 

 pillar, though they are sometimes offensively plentiful upon the cab- 

 bage tribe. They may suffer, but I have never seen any which had 



