﻿188 THE ENTOMOLOGIST. 



get the full bene tit of the damp atmosj^here which is so neces- 

 sary to most species just before emergence. When in addition 

 to this it is realized that the removal of the pupfe, if carefully 

 done, does +,hem no harm, and adds to the percentage of emer- 

 gences, there seems no tangible reason left for leaving pupiB 

 in situ. 



I do not by all this mean that every cocoon should be opened 

 and the pupa removed. As long as the cocoons are fairly sub- 

 stantial, there is no object to be gained by doing more than 

 separating the cocoons one from the other, and removing the 

 loose outer web if there is one. Indeed, from the difficulty of 

 doing so without injury, it is unwise to attempt to remove pupae 

 from very tough cocoons, such as those made by the Dicranura. 

 The old adage that the exception proves the rule was never 

 better exemplified than in the treatment of Lepidoptera ; and in 

 connection with this question of the removal of pupae or cocoons, 

 there are some species whose pupse must be left in the situation 

 chosen by the larvae. The species in which this is so necessary 

 are generally those in which the pupa pushes itself partly out of 

 its hiding-place just before the perfect insect is due to emerge, 

 as, for example, in the Sesias. Then, again, many of the butter- 

 flies, and some species who spin above ground, require the pupae 

 to be suspended in some way, owing to the fact that their imagines 

 prefer to hang from the pupa cases or cocoons while drying their 

 wings. Care must be taken, in the removing of pupas of burying 

 larvae and those which spin up on the surface of the ground, 

 that they are properly formed and hard. Different species vary 

 greatly in the time that elapses between going down and form- 

 ing the pupa. With the generality of burying larvae about a 

 fortnight or three weeks is ample ; but there are several species 

 which rest as larvae for a long time. The most notable of these 

 are the Xanthias and Xnnthnleuca eroceago, which do not change 

 to pupae till about a month before the imago is due to appear. To 

 interfere with such species during the period of rest is generally 

 fatal. 



When dealing with larvae whose period of rest is unknown, 

 the receptacle in which they have gone down should be left un- 

 touched for a fortnight, then the compost in one corner should 

 be gently removed till one of the insects is found ; if it is a 

 thoroughly hard pupa, the lot may be turned out with safety ; 

 if, on the other hand, it is still a larva, leave it, slightly exposed 

 if possible, so that it can be inspected every few days. In this 

 way the period of rest can be found out, and, at any rate, the 

 breeder does not endanger the whole brood. The chief thing in 

 keeping bare pupae over any length of time is to prevent them 

 coming into contact with anything that will block up their 

 spiracles. They should never be allowed to lie on, or in, any 

 dusty material such as dry earth. Bare pupae and cocoons can 



