1918.] 13 



thus cut, the fulcrum jaw is released and takes a fresh point d'crppul a 

 little further hack and the process is repeated. It seems immaterial which 

 jaw takes which function, as I saw first one and then the other used for 

 cutting. 



This came about by an accident that sometimes happens. As a 

 rule, the circle cutting off the lid is fairly good and the end of the 

 cutting meets almost exactly the point at which it began. But this is 

 not always so, and in two or three instances a failure so to meet led the 

 insect to make other tentatiye incisions, in some of which it operated 

 towards the right, in others to the left. It may be asked how I knew 

 what the jaw in the interior of the cocoon was doing. I ascertained this 

 first b}" inference, as the end of one mandible only appeared externally, 

 and it pressed on doing all the cutting, the other jaw being unaccounted 

 for. But towards the end of the process I was able to mise the lid 

 sufficiently to see the modus operandi from the interior. This did not 

 prevent the fly from continuing the process as if undisturbed. Never- 

 theless, in several cases, a beginning to cut the lid was stopped, I could 

 only suppose from my moving the cocoon. When the process was well 

 advanced, the moving of the cocoon to examine the process in action did 

 not lead to an}^ cessation in the operation. The whole process Avhen all 

 goes well takes very few minutes. In one case, however, the fid had been 

 spun rather solidly against a curve of the twig against which the cocoon 

 was fixed, and so the lid did not lift off, and this led to long delay in 

 getting out ; finall}^ the lid was partly cut, partly forced loose from the 

 twig. I met, in this instance, w^ith a curious feature : I forced up 

 the lid sufficiently for the insect to emerge, but it refused to do so, 

 but continued to work at the lid attachment. I experimented in two 

 other instances, offering, by forcing up the not quite separated lid, an 

 easy means of egress, but the inmates would have none of it, but kept 

 on cutting, at once emerging when this was completed. This instinct 

 to comj^lete their task in the proper way gave me a very satisfactory 

 opportunity of seeing the method of working from the inside. 



lieigate. 



Bee. 3;y/, 1917. 



On the introiiudion of Insect Aliens to the British Islands. — Durino- a 

 perusal of the December issue ol' this jMagaziiie"* my attention was arre>ted 

 by some remarks by Mr. E. E. Green on the capture of certain exotic butter- 

 Hies ill the south of Eno-land, conjectured by him to have been deliberately 



» Eut. Mo. Mag. liii, 1917, p. 278. 



