in Pedigree Moth-hreeding. 81 



numbering 244 males and 242 females, — ranging from 

 1,78 mm. to 4.00 mm. There was an excess in each 

 of the seven broods, and the largest male was 41.93 

 mm., the largest female 44.68 mm. In illustmria, 

 though there is a difference, it is not nearly so con- 

 siderable ; in each of six broods, three being of the spring 

 and three of the summer emergence, the female exceeded 

 the male in size. In the spring emergences, numbering 

 more than 300 individuals, this excess on the part of 

 the female ranged from 1.76 mm. to 2.30 mm., the 

 largest male being49. 60 mm., the largest female 52. 20 mm. 

 In the summer emergences of more than 300, the average 

 excess of the female ranged from 2.82 to 4.82 mm., 

 the largest male being 39.50, the largest female 43 90 

 mm.] In brief, the spring female of illunaria is rather 

 smaller than the male, the summer female considerably 

 larger than the male ; in both the spring and the summer 

 emergences of illiistraria, the female is considerably 

 the larger, the difference being, however, less in the 

 spring than in the summer emergence. The conjecture 

 was thrown out last year that the same cause which 

 tends to apterousness in the females of those of our 

 Geometme whose habit is to appear in the winter might 

 be at work in reducing the wing-expansion of the female 

 in one emergence only, — viz., that which takes place at 

 a cold time of year, — of a moth that has also a summer 

 emergence. With regard to measurement I have found 

 the expansion much more easy to measure accurately 

 than the single-wing length is, and therefore, I now 

 always measure the expansion. To convert the single 

 wing measurement into expansion, it should be doubled, 

 adding about l-15th in ilhcstraria, and l-17th in 

 illunaria. With reference to an inquiry made in my last 

 paper, I may mention that the other English species of 

 the genus Selenia, lunaria, rests in the position of 

 illiistraria, not of illimaria. 



Injlaence of temperature on size, cC-c. — I hope the 

 observations wdiicli follow may add to the existing 

 materials for information on subjects that must often 

 have seemed perplexing to those who have bred Lejji- 

 doptera on a considerable scale ; for example, the 

 differences between the spring and summer emergences 

 of illunaria and iUustraria in size and colour ; why in 

 some cases a pupa will yield almost immediately to a 



TRANS. ENT. SOC. LOND. 1889. PART I. (mAP.CH.) G 



