252 THE ENTOMOLOGIST. 



"As is well known, Chelonia caja is one of the most 

 variable of species. Variation amongst insects is a question 

 not less interesting than evolution, and by what circum- 

 stances it is produced has not yet been satisfactorily ascer- 

 tained. Without pretending to have solved the problem, I 

 will briefly relate the result of some experiments I have 

 made with this species, of which I have had six thousand 

 under my care. I had an idea, in common with other ento- 

 mologists, that the food of the larva might influence the 

 colour of the perfect insect. 1 therefore made separate trials 

 with walnut, horse-chestnut, sumach, box, celandine, carrot, 

 and lettuce ; and some I have reared in complete darkness. 

 It will be easily understood why I chose food so diverse. 

 With the walnut, chestnut, and sumach, — trees having a 

 bitter-sweet flavour, — I hoped to produce melanite varieties ; 

 with the box, carrot and celandine, yellow varieties ; with 

 the lettuce, light varieties; and from those kept in total 

 darkness 1 hoped to obtain complete albinism. 



" These, however, are the results of my experiments : — The 

 walnut, chestnut and sumach killed many larvae; a few, 

 however, reached the perfect state, but they were mis-shapen, 

 half-abortive and crippled; in fact, only worthy of figuring 

 in a museum of curiosities. The box was eaten for a few 

 days, but the larvae would then eat no more ; and as 1 did 

 not change the food they all died of starvation. The 

 celandine was eaten greedily; the greater part of the larvas 

 formed chrysalids, but all perished in the cocoon except one, 

 which not having suflScienl strength to develop emerged a 

 cripple, without indicating any kind of variety. As for the 

 carrot, I found nothing worthy of recording. The lettuce 

 only produced pale, dull, discoloured specimens. Those 

 brought up in total darkness all perished in the third change. 

 Such is the account of my experience : food-plants so diverse 

 as to give fair expectation of good varieties produced none 

 worth record. The few varieties which are in my cabinet 

 were all from larvae bred on the usual food-plants, viz. 

 dandelion, chickvveed, dock, groundsel, plantain, &c. 1 have, 

 however, remarked that it was always during slorms, when 

 the air was charged with electricity, that the varieties 

 emerged. Is it possible that electricity is a chief agent in the 

 variation of Lepidoptera } " 



