SCIENTIFIC NOTES AND OB8EEVATI0NS. 87 



uses, under the heads of (1) " Extensible (xlands on the Abdomen ; " 

 (2) " Tufts or pencils of hairs found on various part of the body, in- 

 cluding legs and wings;" (3) "Clusters of scales etc." may be found 

 in Brit. Nod., vol. iii., pp. 6-8 ; also in " Scale jjatches in the male," 

 with an account of abdominal plumes of hair, I.e., p. 14. — En.] 



Apterous females and winter emekgenge. — I trust that the in- 

 terest of the subject may induce you to give me room for a few further 

 remarks on the connection between apterous $ s and winter emergence. 



First, I would thank Mr. Prout for his courteous answer (Eat. Rcc, 

 vol. v., p. 147) to my comments {id., p. 96) on an ojiinion expressed by 

 him {id., p. 86), and for his reference to Mr. Tutt's observations in Brit. 

 Noct., vol. iii., pp. 8-9. 



It certainly does seem, from the reasons there given by Mr. Tutt, 

 that the apterous or semi-apterous state of the ? may be due to distinct 

 causes in the case of winter and summer moths. 



I think that there can be no doubt that all moths, 3" and 2 , vvere 

 originally amply winged, and that, in the case of all apterous or semi- 

 apterous 5 s, three, or possibly four causes have been at work to reduce 

 them to their present state, viz. : (1) disuse ; (2) the survival of the 

 fittest or more atrophied forms, these being less liable to be seen and 

 attacked by their natural enemies ; (3) the increased tendency to 

 atrophy thus inherited by the offspring of a constantly increasing 

 number of atrophied forms ; and (4) possibly increased fecundity due 

 to the diificulty of the species to exist, and the consequent tendency of 

 the wing to become less developed as a set-off ; though my own view is 

 rather that the increased fertility of the J may be the result, and 

 not the cause of less exi3enditure of energy in wing development. At 

 all events, after the first start, the two processes would go on side by 

 side, mutually encouraging each other. The suggestion of Mr. Prout, 

 as I understand it, is that, in the case of winter moths, the cold of the 

 winter season may have a direct inflvience on the wing development of 

 the 2 , bj' affecting her full vitality and fertility, which " might only 

 be maintainable at the expenses of the not-indisj)ensable organs of 

 locomotion." It is the difficulties that I still feel in the way of this 

 view — that cold has any direct influence — which leads me to make a 

 few further remarks on the subject. 



Though both Mr. Prout and Mr. Tutt (loc. cit.) give very good 

 reasons why the particular groups in question may, during the winter 

 and leafless season, require more facilities for hiding, and consequently 

 have less use for their wings, none of the observations of either of them 

 suggest any reason why they alone of the winter moths should be 

 directly affected by cold ; while, as I indicated in my former remarks, if 

 the order of appearance of the HyheriiUdae is considered in connection 

 with the greater or less wing development of the 5 , it seems hardly 

 possible that the cold jier se affects them in this way. It must, I suppose, 

 be admitted that tliere is a turning point, which I should put some- 

 where about the middle or latter part of January, up to which, in 

 normal years (for we are not concerned with abnormal seasons), the 

 winter gradually advances, and after which it gradually retreats. One 

 ouglit then, according to this theory, to find the J s becoming more 

 apterous with the advancing season, till in January a truly apterous 

 form is reached, and from January the ? s becoming less apterous till 

 March or April, when they would again become fully winged. 



