224 Lilian J. Gould's eiperimfints 



July 15th. — The fourth ecdysis took place. Two larva 

 were quite light, four fairly dark brown. 



July 27th. — One larva was spinning up on the roof. 

 One died — a light one. Five larva) were left, one light 

 and four dark ones. 



Aug. 1st. —Another larva was spinning up on the roof. 



Aug. 3rd,— The first larva pupated. Another larva 

 died ; this was a dark one 



Aug 6th. — The last two larvae died ; both dark ones. 



Aug. 7th. — The second larva pupated. 



Total result of the foregoing experiment : — 



Colour. No. of larviTR. 

 Clear light brown, light dorsal lines ... ... 2 



Darker i)rown, dark dorsal lines ... ... 1 



Dark brown, dark dorsal lines ... ... 3 



Total 6 



The lightest of these larvae were nearly, but not quite, 

 as light as the extreme one in cylinder 3, and the darkest 

 about matched the darkly marked two in cylinder 3. 

 None were so dark as the dark larva figured (from 

 cylinder 7) with dark surroundings. The change of 

 colour was perceptible a stage earlier than any others. 

 The food was Salix intellina. 



Cylinder 10.— June 27th. — I placed six larvae in the 

 second stage in cylinder 10. 



July 4th. — The second ecdysis occurred. The colour 

 until now had been uniform dusky brown, like the others. 

 From this time the larva3 began to get lighter. 



July 8th. — For this set also I was intending to use 

 tissue-paper, and on this day applied green, doubled 

 tissue-paper round the cylinder and over the roof, on 

 which larvae were resting, and placed the cylinder in a 

 strong light. 



July 9th.— I removed the tissue-paper on Mr. Poulton's 

 advice. The length of the largest larvae, fully stretched, 

 at this time was 6 cm., that of the smallest nearly 3 cm. 



July 12. — The third ecdysis took place. The larva) 

 were all as nearly as possible of the same shade of 

 brown, a shade intermediate between the darkest and 

 lightest in cylinder 8. The dorsal lines in all were 

 distinct, but none very dark. 



July 19th. — The fourth ecdysis occurred. The length 

 of the largest larva, fully stretched, was 7 era., that of 



