38 Mr. F. Merrifield on the effects of artificial 



if at all, seen among fcliem such conspicuous blue 

 crescents as several of mine exhibit. The effect of 

 exposure to cold continued for a period of from 8 to 9 

 weeks (or for a shorter period if exposed when the pupa 

 is freshly formed) is more marked, generally in the 

 increase of darkness. Further experiments must be 

 tried on this insect, on which I am inclined to think the 

 treatment most likely to produce darkness would be 

 exposure for a considerable time from a very early pupal 

 period to a temperature of about 50°. 



I may add that I am well aware that my exhibits of 

 V. urticce would have been more effective had they been 

 limited to a few extreme examples, but I have been 

 desirous of imparting further knowledge than an exhibit 

 so limited could have conveyed. Some of the most 

 extreme specimens make a near approach to the var. 

 polnris of Northern Europe. 



Bomhyx quercus and var. callunce. — I have not been 

 able to complete my experiments on these, but have 

 obtained some results from temperature, and they are in 

 the same direction as those obtained as to other species. 

 To begin with the true quercus form, " Family A.'' Some 

 recent pupte and nearly full-fed larvae, all stated to be 

 from the same hedge at Windsor, supplied to me by 

 Mr. Edmonds in 1890, were placed at 80°, generally at 

 about a week after "spinning up," but some certainly at 

 a somewhat later stage. I produce seven that emerged 

 in from 29 to 40 days ; they are fair samples of the 

 seven, and are, as will be seen, very light coloured. 

 "Family B." A second lot of 18 were sent me during 

 last summer, also from Windsor. They were a par- 

 ticularly fine and healthy lot ; some of them could not 

 li.ave been very recently "spun up," judging from the 

 time when they began to emerge at the low temperature 

 of about 47°, at which they were placed. Fifteen males 

 emerged in from 39 to 71 days. The first was slightly 

 crippled, owing to the want of proper provision for its 

 reception. I produce the second at 40 days, and the 

 fifteenth at 71 days. Both are, I think, rather dark, but 

 the latest to emerge is substantially darker than the 

 other, especially in its light parts. The 12 intermediate 

 ones emerged in periods ranging from 40 to 70 days. 

 These vary slightly, not darkening regularly, but there 

 is on the whole a tendency, more particularly in the 



