THE KILLING AND PKESERVATION OF INSECTS. 8 



from a broken portion of the nut-shell. The species has also 

 been bred frequently from sweet-chestnuts, as well as from 

 walnuts, by Mr. W. West (Proc. South Lond. Ent. Soc, 1890, p. 

 48; Entom. xxviii. 345). 



It will be noted that the only two species of nuts from which, 

 as far as we know, C. pomonella has been reared, viz., walnuts and 

 chestnuts, have the seeds (i. e, nuts) completely enveloped in 

 lieshy husks : is it possible that this fact can account for foods so 

 widely .different, in other respects, from the apple being volun- 

 tarily selected ? or was pomonella, like so many of the other 

 species of Carpocapsa, originally a nut-feeder, and its predilection 

 lor apples a recently acquired taste? If the latter, and more 

 probable, should be the correct solution, we have little to fear 

 from the ravages of this species to our nut crops. 

 4, Lingards Eoad, Lewisham, December, 1895. 



THE KILLING AND PEESERVATION OF INSECTS. 

 By H. Guard Knaggs, M.D., F.L.S. 



In your November and December issues, two correspondents, 

 Messrs. Fountain and Stafford Chope (Entom. xxviii. 303, 332) 

 respectively attribute to me the opinion that grease is the result 

 ot decomposition, i.e. of '' ordinary decomposition" or putrefac- 

 tion. I am not aware of having ever made such a statement, and 

 do not believe that insects do putrefy under the usual conditions 

 ot being converted into specimens. Some time ago a friend 

 asked me if I could account for the Catocal^ going putrid, and 

 u'^ a '^ *®^^ ^^^^ ^^^ *^ prevent it. Not having heard of 

 this offensive characteristic, I was unable at the time to suggest a 

 remedy. As I could find no one who had met with a like 

 disagreeable experience, and as the question baunted me persis- 

 tently, I again paid my friend a visit, when we had a conversation 

 somewhat m this style : "In which species of Catocala did you 

 say you observed the objectionable property ?" " In promissa and 

 sponsa, " Was it a wet season when they were captured ?" " No 

 the reverse." '' Did you capture them yourself?" " No, they were 

 sent up to me from the New Forest." "In a relaxing box?" *'Yes." 

 I here you are: damp was the solution of the enigma, for under 

 ordinary circumstances the natural moisture of the insect would 

 pass off into the dry atmosphere of a well-ventilated room, and 

 desiccation would result. Putrefaction could hardly take place 

 unless an unusual amount of humidity were present, either inhe- 

 rent in the specimen, or in the surrounding atmosphere." 



As for grease itself being decomposed, there can be no doubt 

 but that soon after exposure to the air it becomes oxidised, and 

 rancidity ensues, with the formation, amongst other products, of 



332 



