THE KNTOMOLOGIST. 139 



from the cocoon, to the aperture previously prepared for the 

 escape of the molli.] Tliis event takes place in June, when 

 the pupa pushes its way out until it projects half-way : here 

 it appears to rest for a few minutes, and then, if the sun 

 shines, it seems to jump from its chrysalis-case, shake itself, 

 and, if a male, flies away ; but if a female it often obtains a 

 male before its wings are dry : on fine mornings the moths 

 emerge from the pupa between 7 and 9 a.m.; in cloudy 

 weather a little later : it will thus be seen that this species 

 takes at least two years to complete its metamorphosis, and 

 from experiments now partially carried out I incline to think 

 they sometimes remain still longer in the larva state. The 

 figure given in Westwood and Humphrey's ' British Moths 

 and their Transformations,' vol. i. pi. vii. fig. 15, from Lewin's 

 plate, Coll. Lin. Soc, represents a physical impossibility, and 

 would lead one to suppose that Sesia bembeciformis laid in 

 pupa without a cocoon : in the first place, the passage for the 

 exit of the pupa, which always projects from the aperture 

 before the perfect insect bursts from it, is depicted not half 

 the size of the pupa inside, — hence escape wotild be impos- 

 sible ; and secondly, the pupa, or rather a pupa, for it is cer- 

 tainly not that of a Sesia, is represented naked, whilst our 

 insect invariably constructs a tough cocoon of strong white 

 silk, which is covered on the outside by the frass or sawdust 

 already mentioned, thus giving to the cocoon a brown appear- 

 ance outside. From experiments made upon trees in my 

 garden, I found them all in a decaying state eight years from 

 the time I placed the eggs of this insect on them ; but by 

 cutting fairly into the tree wherever frass was thrown out, 

 and extracting the larvae, I so far recovered one tree, Salix 

 viminalis, that it now serves me to feed those larvae in my 

 breeding-jars which require that kind of food ; and larvae 

 which 1 have introduced are now throwing out frass from 

 this tree as freely as if the eggs had been laid by the parent 

 on the bark. In order to assist the larvae to enter the wood 

 I bored, with a gimlet, a number of holes, into which they 

 entered with great readiness. Our poplars and willows (two 

 valuable trees for clogniakers, wheelwrights and wireworkers) 

 being so subject to injury from Sesia bembeciformis, we 

 ought to set boys, for about two weeks in summer, to gather 

 the pupa-cases as they project from the trees before the moth 



