in Pedu/rce Motli-hrcriUiuj. 83 



fresh in the recollection of all as a very cold and wet 

 one : in this year a brood of illiuiaria which I forced 

 was larger, in a greater ratio than in last year, than a 

 corresponding brood sleeved, the average expansion in 

 the forced being 39.08, in the sleeved 38.16 : the 

 proportion of perfect moths emerging being also larger 

 in the forced brood than in the sleeved brood. In the 

 1888 summer broods of illustraria the difference is in 

 the same direction, but more marked. Though I did 

 not measure the forced brood, the average size was 

 obviously considerably larger than the corresponding 

 sleeved l)rood. This sleeved brood, as compared 

 with those sleeved last summer, is smaller and poorer 

 in colour in all three lines, A, M, and Z, and 

 has a larger proportion of cripples. I mention the 

 proportion of perfect moths emerging in connection with 

 size, because both seem greatly dependent on 

 healthiness. In the autumn of 1887, out of 359 larvae 

 hatched out and sleeved, I obtained 317 pupae, and bred 

 from them 310 moths, of which but seven were cripples. 

 In the summer of 1888, out of 415 pupa3 of the sleeved 

 summer emergence I bred 394 moths, but fully 87 of 

 them were cripples. The case was a great deal worse 

 with the autumn-feeding sleeved larvae of 1888. Of 394 

 illustraria larvae hatched out belonging to the A, M, 

 and Z lines of descent, only 175 have pupated, and of 

 these many are misshapen, and will die as pupae or be 

 cripples, and the average weight of the pupae is less 

 than 2-3rds that of the corresponding brood last year. 

 Though I do not like to speak positively, I can think 

 of no sufficient cause for this deterioration other than 

 the extreme inclemency of the summer of 1888. The 

 deterioration extends to some pupae I have proceeding from 

 eggs laid by a wild female taken in the New Forest last 

 August; of 26 recently hatched larvae sent me from this 

 female in the second week of September, I have only ten 

 in pupa, and the weight does not average much more 

 than 2-3rds of those of last year ; such superiority of 

 weight as they show over the others being, perhaps, 

 attributable to the circumstance, that owing to their 

 backwardness I forced them for a time in their earlier 

 stages. The pupae in the M line of my sleeved illus- 

 traria are remarkably small, and these happen to 

 have been sleeved on a tree in a particularly cold part 



" G 2 



