1896.] 55 



them to dock (Eumes), the majority however shortly died, two under- 

 took an extra or additional moult, a post-ultimate moult, of these one 

 shortly died, but the other grew immensely, and was, as regards size, 

 rather a promiia or 2l fimbria than a comes. It also died, not so far as 

 I could judge from inherent necessity, but as any normal larva might, 

 and too frequently does, die. As I take much interest in the question 

 of moulting of larvae, I intended some day to repeat this experi- 

 ment, and last September a batch of eggs of comes having fallen into 

 my hands, I made the attempt. The result seems of sufficient interest 

 to report, and though it may be described as a failure, it suggests 

 various interesting points for investigation, when the conditions 

 necessary to success are ascertained. 



The aspect that chiefly interested me was the question as to the 

 definiteness of each larval instar ; so far as my observations had gone 

 this seemed to vary in different species. Orgyia antiqua appeared to 

 vary by one moult for no ascertainable cause. Arctia Caja appeared 

 capable of interpolating an indefinite number of moults, at a stage 

 about two instars before the last. Acronycta alni had dropped one 

 moult in order to make the change from the immature to the adult 

 plumage more sudden, retaining a possibility of reverting to its 

 possession, and then manifesting the last intermediate stage, but this 

 instance of comes was the only uumistakeable trace of another larval 

 instar being capable of following the one normally the last. 



In this experiment when the larvae reached the last instar, I 

 diminished the food supplies, so that instead of feeding up in twelve 

 or fifteen days, they had made but half growth after five or six 

 weeks, and then I placed them on abundant diet. 



In spite of this treatment, a certain number went normally into 

 pupa, others died in attempting to do so ; some few came to grief by 

 way of cannibalism, which was, however, much rarer than might have 

 been expected, and a very few made the effort towards a further larval 

 instar, that I have now to describe. 



These larvae assumed the ordinary appearance and attitude of 

 larvae about to moult, but only two actually succeeded in doing so, 

 two or three others partially succeeded, but the others failed to do so, 

 and their true condition could only be ascertained by artificially re- 

 moving the larval skin. 



In so far as regards the body generally, markings and so forth, 

 the larva was quite normal, but larger (and darker). The prolega 

 seemed normal as regards form and retractility, but in no instance 



