SOCIETIES. 91 



course by any specific complaint ; and this appeared not only in mark- 

 ings but also in many instances in the shape of the wings, which 

 usually altered in the direction of breadth. When these causes 

 operated in nature it was a result in one case of a want of succulence 

 in the food, for in very dry seasons when plants were scorched up, a 

 tendency was shown to the production of small imagines, and the 

 same resulted from semi-starvation when a sufficiency of food was 

 unattainable. These conditions resulted in lessening the size of the 

 imago, the density of the scaling, etc. Alpine species were often 

 deficient in this latter particular, and this, it was inferred, was caused 

 by continued exposure to severe weather and to insufficient nutrition. 

 Examining Mr. Merrifield's experiments in accordance with these views, 

 Mr. Fenn assumed that all the specimens exhibited would be found to 

 belong to the artiticial group for these reasons. Most of the species 

 experimented on were double-brooded, and the experience we possess 

 in breeding Lepidoptera shows us that although we may hasten a 

 summer brood yet we cannot turn the spring form into the summer 

 one, the reason being that the extra development of the insect in the 

 larva or pupa state has determined the imago, and that we cannot put 

 back the hands on the clock of nature or reverse what has been already 

 done. Mr. Merrifield himself admitted this. There was another point 

 to which he would direct attention, and that was the temperature neces- 

 sary to alter the colour of the insect — 87° to 57°, and whatever may 

 have been done by artificial means, in a state of nature the lower even 

 of these temperatures was amply sufficient to put all our autumnal, 

 winter and spring species entirely out of its influence, for, to quote Mr. 

 Merrifield, " I find that three days (and, I presume, nights) are all that 

 are sufficient to effect this change." Now a period of three days from 

 September to April or part of May, when the temperature never fell 

 below 57°, is at the least unusual, if not almost unknown, in this country. 

 In Mr. Merrifield's paper, published in the Transactions of the Entomo- 

 logical Society, I find that with regard to 6'. illustraria 60° to 73° is 

 sufficient to produce the change in the direction of heat, and this makes 

 it a matter of impossibility for the spring brood of illustraria in a 

 natural state to be affected at all. Respecting the single brooded 

 species, E. autiininaria is one insect particularly relied upon. In 1884, 

 being fortunate enoug'i to take three $ examples of this insect at Deal, 

 two of which deposited eggs ; by keeping the broods separat^^ly, and by 

 judiciously crossing them, the strain was kept up for several years. 

 Hundreds of the imago were reared, and Mr. Fenn submitted a very 

 long series bred under purely natural conditions in which even greater 

 extremes of variation were apparent than in any of those artificially 

 treated by Mr. Merrifield, but by far the greater proportion followed 

 the coloration of their parents. With regard to the range of temperature 

 necessary to affect autuinnaria, 73° to 80°, it might be assumed that either 

 of these temperatures was quite unusual for a period of three days and 

 nights at the time w-hen autumnaria was bred in confinement (August) 

 or taken at large in September, yet we bred either dark or pale 

 autumnaria following in a great degree the colour of the parent moths. 

 It was pointed out how many of the specimens exhibited showed a 

 tendency to crippling or deformity, plainly indicating that their consti- 

 tutions had been tampered with in some previous state, and this was 



