the colours of certain Lepidoptera. 451 



even including the " ladder " by which it ascended the 

 side of the cylinder. To-day (Dec. 17) I opened it, and 

 found, as I expected, the unfortunate larva shrivelled up, 

 and an ichneumon cocoon lying beside it. Thus a dis- 

 tinct brown (by no means light brown) cocoon was spun 

 by a larva which had been subject to almost every kind 

 of disturbance — removed from a partially constructed 

 cocoon, bearing the external eggs of a parasite, and muti- 

 lated. 



In this case I think it is probable that the instant 

 change in the colour of the silk, noticeable in the threads 

 of the "ladder," and the framework around and beneath, 

 no less than in the cocoon itself, is probably in some 

 way associated with the irritation to which the larva had 

 been subjected. The case suggests, although it does uot 

 prove, a source of the colouring matter other than that 

 provided by an extract from the food, contained in the 

 digestive tract ; that is, so far as this species is con- 

 cerned. It was also certain that in this particular case 

 the silk was not darkened by the larva at some later time. 



Another experiment of the same kind did not lead to the 

 same results. A larva had begun to spin a white cocoon 

 in a similar chip box. It had only constructed the 

 platform when it was removed and wrapped in many 

 folds of black net. Here it began to s])in a white cocoon, 

 but soon died without completing it. As regards this 

 case, it may be remarked that we have no evidence as 

 yet of the effect of black net or black paper upon normal 

 larvae of this species, although we should suppose that 

 dark cocoons would be produced. 



I think that these experiments, few as are the indi- 

 viduals made use of, prove the existence of some power 

 of colour-adjustment in this genus; for such experiments 

 as were conducted were specially arranged to avoid the 

 sources of error present in the earlier ones. 



Then, too, Mr. Tutt's observations upon the allied H. 

 cldorana afford very strong confirmation ; for it is hard 

 to see how any disturbance of his larvie, sufficient to 

 account for the colour change, can have arisen. (See 

 ' The Entomologist's Kecord,' Jan. 15, 1892, pp. 9—12). 



Rumia cratcegata, 1892. — Two beaten larvae of this 

 species spun very light brown transi)arent-looking 

 cocoons in pieces of white tissue-paper in the cylinder 

 described above as exposed to light. Both larvae sought 



