^^ AND ^^/^jjt 



JOURNAL OF VARIATION. 



No. 8, Vol. V. August 15th, 1894. 



JNfotes on the Variatioii of ^pilosoma mendica 



With some thoughts on the Ancestral Type of the Genus. 

 By J. W. TUTT, F.E.S. 



A few years ago (1885), British entomologists were startled by the 

 capture of a pale form of the male of Spilosoma mendica, in Co. Cork, 

 Ireland, by Mr. H. McDowall. Tlie species, as is well-known, is usually 

 in this country very distinctly sexually dimorphic, the males being of a 

 deep sooty-brown colour, whilst the females are white with a few 

 scattered black spots, and are much less thickly scaled than the males. 

 When Mr. McDowall discovered this pale form in Ireland, he captured 

 a male and a female, and from the latter was fortunate enough to obtain 

 eggs which he distributed to many English collectors, among others to 

 Mr. R. Adkin of Lewisham. That gentleman took special pains in 

 rearing the larv?e which hatched from these eggs, and made many 

 observations on their habits and economy ; he was, however, unable to 

 detect any difference between them and those of our ordinary form, and 

 they puj^ated in a similar manner. 



Many specimens, the outcome of these eggs, were distributed 

 throughout our collections, but comparatively few individuals have since 

 been taken at large. Three specimens were taken at light in Antrim 

 in 1886, and five in the following year, one of which was almost jnire 

 white. Mr. W. F. de V. Kane is responsible for the statement tliat 

 another specimen was taken in Co. Cork in (or before) 1885. Females 

 have been taken in Dublin and Waterford, but what form of male occurs 

 there has not yet been determined. It would appear, however, that no 

 very dark male has as yet been taken in Ireland. 



In England, the species does not, as a rule, tend to vary, but a few 

 remarkable cases of variation have been recorded. From eggs obtained 

 from a female taken at Eltham, by Mr. C. Fenn, 21 males and 22 females 

 were bred. The females varied little from the ordinary tyjje, except in 

 the case of one specimen which was curiously blotched with dark grey 

 on the left fore- wing. The males varied from specimens of the usual 

 English type, to others of a dull pale yellowish-grey, and quite 50 per 

 cent, diverged more or less from the usual blackish-grey form. The 

 pupaj were exposed to the weather in a very cold and damp spot, and 

 it has been suggested by Mr. Fenn, that these conditions upset them so 

 as to produce this large amount of variation. Another very similar 



