24 



THE SUSPENSION HABIT IN YOUNG 

 CATERPILLARS. 



LLEWELLYN LLOYD. 



Speaking of Ichneumon-flies in the Cambridge Natural History, 

 Dr. Sharp says : — ' It is very difficult to observe the act of 

 oviposition ; the Ichneumon-flies usually decline to notice 

 caterpillars with which they are placed in confinement. Occa- 

 sionally, we may, by a happy chance, observe the act in insects 

 at large, and from the records of observers, it may be deduced 

 with tolerable certainty that the sense of sight takes no part 

 in the operation.' 



Dm-ing last August I was watching an Ichneumon-fly 

 hunting caterpillars in a Leeds garden. It found a small 

 caterpillar suspended from the edge of a leaf. Without seeming 

 to hesitate it flew to the leaf and bit through the thread causing 

 the caterpillar to fall on to a leaf below. It flew straight down, 

 seized it, and drove in its ovipositor three times. It would 

 have been absolutely impossible for the fly to do this while the 

 caterpillar, which was the smaller of the two, was in suspension. 



I failed to secure the Ichneumon, and so do not care to 

 hazard a guess as to what species it was. In the first place, it 

 seems certain that sight was a most important factor in the 

 series of actions. It may have found the larva by a sense of 

 smell, but how could it have found and cut the thread without 

 the sense of sight coming into play ? 



Secondly, we can hardly imagine that all Ichneumons would 

 be intelligent enough to cut loose suspended larvae. Granted 

 this, the habit of suspension must be of great use as a protection 

 for larvae against these parasites. Ratzeburg considers that 

 Ichneumons only attack caterpillars in a deficient * state of 

 health, but I have reason to believe that they also attack 

 young forms. The suspension habit is especially developed 

 in young caterpillars. 



We are pleased to see from the ' Annual Report of the Natural History 

 Society of Northumberland, Durham and Newcastle-upon-Tyne,' that the 

 Society has received a legacy of ;/|6ooo. This will materially assist it in 

 its work. 



* We should think it more likely that they avoid unhealthy larvae. — 

 G.T.P. 



