BULLETIN OF THE BROOKLYN ENT. 80C. 27 



The uses of Cocoons. 



Some time since, in a French Ent. magazine an article appeared, 

 criticising the opinion which had been before advanced that co- 

 coons served to keep the pupae in comparative warmth. 

 The writer took the gronnd that cocoons were for the purpose of 

 protection, the insect in making them, mimicking dead leaves etc. 



And he denied their use for warmth, as experiments had proved 

 there was no practical difference in the temperature of the air 

 within and without the docoon. 



This articlo has led to some thought upon the subject, and we 

 are led to believe the following uses are obtained in the cocoons of 

 insects. 



1. It is probable that there is a slight addition to the tempe- 

 rature of the inside of the cocoon by the living body within it. 

 Though of course, the quantity amounts practically to nothing, as 

 proved by the experiments. 



2. "We do not believe in the mimicry theory. Mimicry does 

 not explain everything otherwise inexplicable. All cocoons are 

 not by any means the color of dead leaves ; and very few have 

 that appearance save by exposure to the weather. Very many are 

 surrounded with dead leaves which serve to conceal, but the leaves 

 seem to be chosen as a convenient basis for the framework of the 

 cocoon and not for concealment. Small branches seem to bt 

 chosen even more freely, where they answer the same purpose. 



3. Cocoons are without doubt of use in tempering rapid 

 changes in temperature. We have roses, for example, which we 

 protect in winter with a straw covering. This is not for heat, but 

 to prevent death by the freezing and thawing of our early spring. 



We think the cocoon answers the same purpose. Our experience 

 shows, that a long winter of steady cold is much less destructive 

 to pupae than a changeable winter though on the average a warm 

 one. 



4. Cocoons are without doubt of use in preventing the loss of 

 moisture by the pupa. The pupa of the Cecropia or Polyphemus 

 moths, exposed to the atmosphere without its natural covering will 

 as a rule dry up or produce an imago which will not have moisture 

 enough in its tissues to properly expand its wings. This we have 

 seen in numerous examples. 



