2^6 THE ENTOMOLOGIST. 



ON THE VARIATION OF INSECTS. 

 By T. D. a. Cockerell. 



(Continued from p. 178.) 



Class v.— Variation of Pup^ and Cocoons. 



It is now perfectly well established that many cocoons and 

 exposed pupse of Lepidoptera vary very considerably in colour, 

 mainly in the direction of resemblance to the tint of their 

 surroundings. Of these the following may be quoted as in- 

 stances : — ♦ 



Pupce. — Vanessa gonerilla, light and dark varieties (Entom, 

 xvi. 218) ; V. urtica, light and dark varieties were produced by 

 Mr. Jenner Weir by modifying the amount of light at the time 

 of pupating : those in the shade produced the darker forms. 

 Melitcea harrisH, Scudd., the typical pupa is white, marked and 

 spotted with black, or brown-black, and orange ; a variety is 

 almost without the black markings, but has the orange (W. H. 

 Edwards, Canad. Ent. 1877, 168). Lyccena comyntas, pupa from 

 larva fed on Desmodium marilandicum is emerald -green, with a 

 yellowish green abdomen, but the pupa from larva fed on clover 

 is sordid white, with the wing-cases apple-green : both forms 

 have also some markings (W. H. Edwards, Canad. Ent. 1876, 

 204). Papilio ajax, L., varies from dead-leaf brown to bright 

 green ; and P. asterias, Fab., from pale green to ochre -yellow 

 and ash-grey. It has been said that the green pupae of P. asterias 

 emerge sooner than the dull-coloured ones, but I do not know 

 whether this would hold good in a large number of cases. Last 

 year I had a green and a brownish pupa of this species, and the 

 green one gave a crippled butterfly on October 28th, while the 

 other remained over until this year. No doubt the heat of the 

 room brought the green one out thus early, but there was no 

 apparent reason why it should not similarly affect the brown 

 variety. 



Cocoons. — Samia cecropia, (a) on red currant, silk deep 

 reddish brown ; (b) on cherry, plum and rose, light brown, tending 

 to f^rey ; (c) on Spircea, SympJioricarpos and Prunus serotina, 

 tjreyish brown (T. Gr. Gentry, Canad. Ent. 1877, 49). The 

 experiments of Mr. E. B. Poulton to prove that the colours of 

 cocoons are really influenced by the colours of their surroundings 

 are very well known. Cocoons of Saturnia pavonia were dark 

 brown when the larvae were placed in a black bag, but white when 

 they had been freely exposed to light, with white surfaces in the 

 immediate neighbourhood. Larvae oi Eriogaste?' lanestris exposed 

 to white surroundings produced cream-coloured cocoons, while 

 some of the same batch spun dark brown cocoons among the 

 leaves of the food-plant. Larvse of H alias prasinana exposed to 



