36 Mr. F. Merrifield on the efects of artificial 



divisions respectively placed at two different tempera- 

 tures, viz., at 80°, and at about 46°. Every one of those 

 (rejecting a few cripples), mostly among those at the 

 higher temperature, at 46°, is darker than any of those 

 at 80°. 



A sixth family, of the spring emergence (Family "U "), 

 numbering about 20 individuals, was exposed to several 

 different temperatures for varying periods. These show 

 the same general results, but of course not so definitely 

 as the others ; moreover, they proved to be an unhealthy 

 family, of which many died, or came out in a crippled 

 condition. I exhibit typical specimens of each of these 

 6 families, also of 5 others, showing the same general 

 results when exposed to similar conditions. 



P.falcataria. — With an experiment on this I will con- 

 clude my summary of recent results, so far as concerns 

 double-brooded GeometrcB. I was supplied during the 

 winter with a number of pupae, which were very small 

 and poor, as well as much tenanted by parasites, so that 

 only 7 emerged. Three of these were placed, on the 

 19th April, at 80°, emerging in from 5 to 9 days, the 

 others, left out of doors, appearing between the 21st and 

 29th May. With one doubtful exception those which 

 emerged in the open air are manifestly darker and more 

 strongly marked than any of those at 80°. I exhibit all. 



V. iirticce. — In December, 1890, I exhibited a very dark 

 specimen of this insect, the appearance of which I then 

 thought, and have now no doubt, resulted from the 

 exposure of its pupa to a temperature of about 47° for 

 5 weeks. I again exhibit this specimen, with a fair 

 sample of 4 others of the same lot, all brought out at 

 80°, and emerging in about 6 days (Family "Y"). 

 During the last summer I have experimented on three 

 different families (or rather batches, each collected at the 

 same time, and in similar localities). The first two, 

 which I will call "V" and "L," were very kindly given 

 to me by Mr. Vine; "V" about the end of June, to the 

 number of more than 100. I was under the impression, 

 derived from m_y experiments with the Gcomctrce, that 

 any change in colouring would be produced during one 

 of the later pupal stages, and therefore took no pains to 

 place the pupne while quite fresh in the refrigerator ; and 

 this may have been the cause of the comparatively slight 

 effect produced on most of them, that effect becoming. 



