156 THE ENTOMOLOGIST. 



the opinion, which might be held, that light influences the for- 

 mation of colour in the wings of butterflies through the pupal 

 integuments. 



The experiments were carried out ten years ago, and their 

 purely negative result made a description of them appear to me 

 superfluous. I describe them solely that this question may be 

 set at rest ; and I do so, although I now see that Dr. Standfuss 

 has undertaken and published similar experiments, in which the 

 result was likewise negative.* 



Experiments ivith Vanessa cardui, 1884. — A female of V. 

 cardui, captured in the open near Freiburg, laid numerous very 

 small green eggs on a thistle on May 27th, 1884 ; they were all 

 laid singly on the under side of the leaves and on the stem, but 

 often several (up to nine) scattered on the same leaf. 



The emergence of the larvae took place between June 4th and 

 Gth, with exclusion of the light under a black bell-glass. The 

 larvae which had emerged were then divided into three groups, 

 the first of which remained in darkness, the second was reared 

 under blue light, and the third under yellow light. 



All of the third group escaped through an opening, and had 

 to be replaced by five larvae from the first group on June 19th ; 

 and, as these died in the yellow light, they were again replaced 

 on June 21st by some of the first group. 



The larvae of all three groups then developed equally well. 

 All the larvae of the second group pupated on July 3rd, all but 

 one of the third group on July 4th. The larvae reared in dark- 

 ness did not pupate until July 8th. However, this cannot be 

 attributed to the light without further proof ; it was rather only 

 a result of worse, i. e. slower, nutrition. The box, in which this 

 group was reared, was, indeed, only closed by its lid, and not 

 with a glass plate, as in the second and third experiments. To 

 be sure, a thick cloth lay over this, but still the evaporation was 

 great, and caused the food-plant to dry rapidly. The renewing 

 of the food-plant, too, always brings about a kind of fast, as 

 the larvae are very sluggish, and do not readily crawl of their 

 own accord from the withering leaf, although a fresh one lies 

 close by, or even just over it. They then, indeed, spin both 

 together, but they eat the withered one again notwithstanding. 

 They are not adapted to a change of food, but to remaining 

 stationary on the same plant. The butterflies emerged — 



3rd Group, under 

 yellow light. 



On July 11th, 5 



two of which were 



crippled. 



-'' Standfuss, Handbuch fiir Sammler europaischer Grosschmetterlinge. 

 Guben, 1891, p. 119. 



1st Group, in the 

 dark. 



On July 13th, 2 

 „ 15th, 2 



2nd Group, under 

 blue light. 



On July 9th, 1 

 „ 10th, 4 



