SCIENTIFIC NOTES. 273 



that exposing the [)upa to a low or moderate temperature, as contrasted 

 with a high one, is in some species a principal cause of darkness of 

 colouring in the perfect insect, but go far to localise the period of the 

 pupal stage at which the temperature so operates, and to show that 

 changes in markings and in colouring, are respectively due to different 

 applications of temperature. As to moisture, I am by no means pre- 

 pared to say that it is not one of the causes, though some experiments, 

 specially directed to this point last summer, tend to show that moisture 

 has little or no appreciable effect on the colouring of the species 

 operated on — autumuaria and illustraria. The remark you quote 

 from a letter to the effect that the governing consideration is — which 

 brood arn I to belong to — and as to " converting one form into the 

 other," was made with reference to double-brooded species, in which 

 each of the seasonal forms habitually carries with it special qualities of 

 size, markings, colouring, etc. Here the question which of the two 

 forms the moth shall belong to — and thus, indirectly, what shall be its 

 colouring — would usually be determined before the end of the larval 

 stage. Experiments made last summer have shown, however, that 

 even in these cases the markings and colouring may be greatly affected 

 by the temperature to which the individual pupa is exposed. — F. 

 Merrifield, 24, Vernon Terrace, Brighton. Dcce7nber, 1890. [It is 

 with the greatest pleasure that I print Mr. Merrifield's opinion of my 

 criticism of his paper, and the inferences I drew from it, and feel satis- 

 fied, that much as T differ from him as to the cause which produced 

 the effects noted, that only a careful consideration of all possible views 

 of the question can lead us to even a moderately correct solution of 

 this matter. — Ed.] 



Fecundation before Hybernation. — I have frequently captured 

 Vanessa urtica in copula after hybernation, but never before ; in fact, 

 the sexes appear to have very little attraction for each other before 

 hybernation. — VViM. Newman, 21, Russell Street, Darlington. 



I see by this month's Record, that you ask for any notes on the 

 pairing of insects before hybernation. I once took Colias hyale in 

 copula in August, and I believe that species hybernates in the perfect 

 state. — A. W. Mera, Forest Gate. December, 1890. [I doubt whether 

 this species normally hybernates in the imago state although instances 

 are on record of its doing so. — Ed.] 



Cause of Aneurism. — Aneurism of the wings is, I fancy, entirely 

 an artificial condition, and is caused by the insect failing to maintain 

 its foothold, when the wings are partially expanded ; in the fall, the 

 larger nervures or wing-rays are bruised or bent, and this causes the 

 expanding liquid to be dammed up at the points of injury, thus 

 causing the apparent aneurism. — C. Fenn, Lee. November, 1890. 



I do not agree altogether with my friend Mr. Fenn as to the cause 

 of aneurism, although a somewhat similar appearance might be pro- 

 duced from the injury noted. I believe the mechanism of develop- 

 ment of the wings is as follows: — (i). A gradual unrolling of the 

 hollow spiral nervures by the propulsion of air along them, the 

 nervures being simply extended tracheal passages (the movement of 

 the insect at the time will explain this). (2). The upper and lower 

 membranes are stretched out, as the wing-rays or nervures unfold, 



