Volume TIT JUNE, 1918 No. 1 



ON AN INHEEITED TENDENCY TO PRODUCE 

 PURELY FEMALE FAMILIES IN ABRAXAS 

 GROSSULARIATA, AND ITS RELATION TO 

 AN ABNORMAL CHROMOSOME NUMBER. 



By L. DONCASTER, MA., 



Fellow of King's College, Cambridge. 



I. The Inheritance of Unisexual families. 



It is well-known that in Lepidoptera, families are occasionally 

 produced which are all or nearly all of one sex. This has sometimes 

 been observed as the result of hybridizing distinct species (e.g. Tutt, 

 Trans. Entom. Soc. 1898, p. 17. Three matings of Tephrosia histortata % 

 X T. crepusculariaj gave 40 c/, ? ; 58 (/•, ? ; 60 c/*, 1 ?), but not 

 rarely families consisting wholly of males or of females have been 

 recorded when both parents have been apparently normal members of 

 the same species (cf Lamborn's experiments with Acraea encedon 

 {Proc. Entom. Soc. 1911, p. liv) referred to below). 



In 1908 I received from the Rev. G. H. Ray nor a batch of larvae of 

 Abraxas grossulariata, obtained by mating a wild female with a lacti- 

 color male (No. '07.19^). From these I reared 19 moths, all lacticolor 

 females, and heard from Mr Raynor that from the same family he had 

 bred 21 lacticolor females, making 40 in all. Of my females I paired 

 four, one with a lacticolor male, three with grossulariata males all of 

 which were heterozygous for lacticolor. The pairing with a lacticolor 

 male (^08. 2) gave 27 lacticolor females and no males ; from one of the 

 other pairings no images were reared ; the remaining two gave respec- 

 tively 40 </•, 23 ? , and 5 c/", 2 ? . Of the 27 females in family '08. 2 I 

 paired six, three with lacticolor males, three with grossulaHata males. 



1 The reference numbers of purely female families are italicised. 

 Joum. of Gen. iii 1 



