316 Mr. 'Pou.Mon' 8 farther experiments upon 



15. Experiments in 1889 upon the larvte and 

 COCOONS OF Hemerophylla abruptaria. 



A captured female laid the eggs from which were 

 obtained the larvae employed in the following experi- 

 ments. The great majority of the eggs hatched June 5, 

 a single larva appearing on the 4th. They were fed 

 together until June 17, when the experiment was begun. 



Experiment I. 

 Dark Surrounclings. 



June 17. — 20 larviu of an average 

 length of 7*4 mm., and most of them 

 12 days old, were introduced ; many 

 very dark twigs (of Qucrcua cerrix, 

 &c.) being intermixed with the food- 

 plant. 



June 30. — Larvit; compared. 

 There was a most remarkable differ- 

 ence between them, these being very 

 dark, almost black. The effect had 

 thus become marked in 13 days or 

 under. The larviu were of an average 

 length of 15-0 mm. 



July 14. — All the 26 were alive, 

 and very uniformly dark. Their 

 size was about the same as those of 

 Experiment 11. 



July 25. — 2 larviTG had spun up. 

 The 24 remaining larvffi were com- 

 pared for the last time with those 

 of II. The difference was wonderful, 

 and there was no exception on either 

 side. 



July 2G. — 1 larva had spun up. 



Experiment II. 

 Green Surroundings. 



June 17. — 25 similar larva? sur- 

 rounded by leaves and green shoots 

 of lilac. Leaves of similar age and 

 from the same plant were supplied 

 to I. Up to this date the 51 larvjc 

 had been fed under the conditions 

 of II., viz., among leaves and shoots, 

 without the intermixture of any dark 

 sticks. 



June 30. — The darkest of these 

 larva; were probably lighter than 

 the lightest of the others. 



July 14. — The largest larva^ were 

 31-0 mm. long, and were nearly 

 full-grown. The most usual length 

 was 25-0 ram., some 3 or 4 being 

 much shorter (about 18-0 mm.). All 

 25 were alive. The colour was ex- 

 tremely uniform, being a pale brown 

 with a greenish tinge in the lightest 

 individuals. 



July 25. — 24 larvre still feeding, 

 and compared. Both lots were 

 photographed at this date. 



July 26. — 6 of the largest larvre 

 were put under the conditions of I., 

 but there was no change. 



These larvae are thus seen to be extremely sensitive. 



I was kindly helped by Mr. G. J. Burch in photo- 

 graphing the larviu. Isochromatic plates were used, 

 and the most favourable results were obtained when 

 the larvae were exposed for 30 seconds to the light 

 from a small magic lantern (with a paraffin lamp), after 



