BT R. J. TlLLYAlil). 225 



towards the imaginal stage to Ije of any use. In this way the 

 most promising cocoons (i.e., the largest) were all wasted. 



By this time both Chri/iiopa A and Chrysopa B were spinning 

 up, so I turned my attention to the larger of the two (A). Here 

 an additional difficulty presented itself in the smallness and 

 greater delicacy of the cocoon, and the activity of the pupa 

 Avithin it. The cocoon could not be cut open with fine scissors, 

 owing to the fact that the pupa would keep wriggling round so 

 as to face the cut, and thus sooner or later the delicate wing- 

 cases became damaged, either by pressure or by the lower point 

 of the scissors. I next tried to open a cocoon by means of a fine 

 sharp needle, and was delighted to find that this could be done 

 without damaging the wings of the pupa, if certain rules were 

 adhered to. Firstly, owing to the method of 

 spinning the cocoon, it appeared that the silken 

 envelope does not tear unevenly in all directions, 

 but can be made to split exactly along any parallel 

 of latitude (taking the ends of the Icmgest axis as 

 the poles) if the point of the needle is exerted in 

 that direction. Secondly, if the point selected to ,„ 



, . 1 .1 ifXt-fig. 1." 



start on is at about the level of the lid of the cocoon 

 when opened by the pupa itself naturally, the split comes \ er\' 

 readily, and the point of the needle is not likely to touch the 

 wings of the Avrigglesome pujia. This position is about the same 

 as that selected when "topping" a boiled egg at breakfast, and 

 is shown in Text-fig. 1 . 



Having solved the problem of how to open the cocoon without 

 damaging the pupal wings, the next difficulty wa;^ to extract the 

 })upa, which, as soon as the lid of the cocoon was lifted, became 

 very actiAe, and kept wriggling round from sifle to side, so as 

 always to face the point of the needle. I found the best plan 

 was to continue the cut until the lid could be either taken com- 

 pletely off, or turned over backwards, so as to expose the head of 

 the pupa. If now the pupa, as it generally did, resolutely re- 



* Cocoon of L'hr>/-^opa xiijiuifa Walk., cofiectlj- opened: ( - (i). 



