THE ENTOMOLOGIST 



Vol. XXX.] AUGUST, 1897. [No. 411. 



SPILOSOMA MENDICA AND ITS vae. RUSTIC A 



INTEEBRED. 



By Robt. Adkin, F.E.S. 



The concluding sentence of the note on " Hybrid and Mongrel 

 Lepidoptera " (ante, 197) renders desirable the publication of 

 details of the pairing of the English and Irish forms of Spilosoma 

 mendica which I obtained some time since, but which have not 

 previously been placed on record. 



The stock from which the Irish form (var. rustica) was reared 

 I received as ova in May, 1886, it having then been once inbred 

 (Proc. South Lond. Soc. 1887, p. 90), the parent moth having 

 been taken in Co. Cork. The English stock (typical mendica) 

 came to me some three weeks later, also in the form of ova, and 

 once inbred from a moth taken in the north of London. In 

 each case fine broods were reared in 1887, the largest Irish 

 males measuring 40 mm. in expanse, thus comparing favourably 

 with the only two captured Irish examples I possess, which both 

 expand 36 mm., and the largest females of the brood measure 

 46 mm. The English males reared in 1887 expanded 36 mm., 

 and the females 42 mm. Ova were obtained from both broods, 

 but the larvae resulting began to show signs of degeneracy, the 

 percentage of deaths being larger than in the previous genera- 

 tion, especially among those of the Irish brood ; and the imagines 

 emerging in 1888 were slightly smaller, the largest Irish male 

 being 88 mm. and females 42 mm. in expanse. Thus far the 

 English moths had all emerged before the Irish began to appear 

 (possibly the removal northward may have accounted for the 

 lateness of the latter), thus preventing the possibility of the 

 cross-pairing I so much wished to obtain. Continuing the 

 broods, further signs of degeneracy manifested themselves ; 

 many ova did not hatch, the larvae were sickly, and a large per- 



ENTOM. AUGUST, 1897- S 



