experiments on some Lepidopteya. 141 



that which proceeds from the autumn pupa, is not the 

 same in colour or in markings. 



(b) Autumn pu2)a of ilhisti-Avia,; effect of forcing, d-c, 

 on vigour. — This converse experiment affords a striking 

 contrast as regards its effects on the vigour of the 

 insect. 



Of 36 pupfe so treated in the autumn of 1887 (Tables 

 XVI. and XVII.), only 12 emerged, and of these 7 were 

 cripples, and only 5 perfect, or nearly so ; and of these 

 5, 4 had been exposed some weeks after forcing to severe 

 cold out-of-doors for about 5 weeks before the forcing 

 was resumed. 



Of another lot of 63 belonging to a not very healthy 

 brood— for two-thirds of the larvae died — 18 were kept at 

 the moderate temperature of about 60°, and of these 

 only 4 emerged, 2 of them being cripples. The rest, 

 45 in number, were placed out-of-doors, and of these 32 

 emerged, only 3 of them being cripples. 



Of the pupfe lent me by Mr. Jenner (as mentioned Ent. 

 Soc. Trans., 1889, p. 92), being a brood which, except two 

 individuals, laid themselves up for winter pupation instead 

 of emergence in July, 26 were forced (Table XIX.), and 

 only 13 of these emerged, of which 4 were cripples. 

 This was a very healthy lot, for about 30 of the same 

 brood, which were left to winter in a cool room, nearly 

 all emerged in perfect condition. 



All that were thus forced showed great irregularity in 

 the time of their emergence, and they all seemed less 

 thickly clothed with scales than normal specimens are, 

 whether of the autumn pupa or of the summer pupa, 

 the moths from which last are in general the most 

 thickly clothed with scales. 



The irregularity caused by forcing the autumn pupa 

 at different periods is illustrated by Table XVIII. , 

 relating to a very healthy lot of 20 pupa. This Table 

 affords evidence that the irregularity is caused by forcing 

 the autumn pupa at a time when it would naturally 

 remain for months in the pupal condition, for the 

 irregularity ceased when the forcing was postponed until 

 the autumn pupa had been 4 months in that state. 



Effect on colour and markings. — All the moths are 

 intermediate in colouring and in markings between the 

 summer and the spring emergence. Such as were 

 exposed to cold during part of the pupal period are con- 



