H. Onslow 139 



three non-radiated ^^ and % % , which would result from the hypothesis 

 that radiation is recessive, and that both parents were heterozygous, is 

 closely approached by the actual figures. It is, however, an hypothesis 

 that takes no heed of the remarkable sex ratio which shows a large 

 preponderance of males. 



There are not at present enough data to determine whether this 

 disturbance of the normal sex ratio can be explained better by the action 

 of a lethal factor or not, but the work is being continued. 



In conclusion my thanks are due to the British A,ssociation for 

 defraying part of the expenses of this research by a grant during the 

 year 1920. I am also much obliged to the Rev. G. H. Ray nor both for 

 the data and for the living material he has so kindly allowed me to use, 

 and to the editors for their kindness in reading this paper. I am especially 

 grateful to Miss Helen Moodie for her care of the larvae, and the 

 resulting large families. 



DESCRIPTION OF PLATE XIX. 



Abraxas grossnlariata and varieties. Natural size. 



1. Var. varleyata $ with broad white collar showing discoidal spots. 



2. Var. varleyata ^ with black stripe crossing collar from basal shoulder knot to 

 discoidal spot. 



3. Var. varleyata $ with narrow collar showing spread of black pigment outwards from 

 basal shoulder knot. 



4. Var. varleyata 9 except for a white fleck the collar is restricted to the hind wings. 



5. Grossnlariata 5 > type, showing normal pattern. 



6. Grossnlariata $ showing increase of black pigment, also stripe as in No. 2. 



7. Var. leucosticta ^, a black insect showing traces of two white radii near margin of 

 hind wings. 



8. Var. leucosticta ^ showing number of incomplete radii on hind wings. 



9. Var. actinota ^ showing fully radiated hind wings with traces of radiation on fore 

 wings. 



10. Var. varleyata ^ showing, like No. 4, almost complete absence of white collar on 

 fore wings. 



11. Var. hazeleighensis ^ showing considerable increase of black piginent, though the 

 white areas are rather too extensive for this variety. 



12. Var. hazeleighensis ^ showing black pigment almost entirely covering the fore wings. 



Note. Those insects whose fore wings show a great increase of black pigment have 

 little or no corresponding increase iu the hind wings. 



