266 ' Genetical Studies in Moths 



maria is derived from it, the anomaly may therefore be ancestral in 

 cause. 



The Fi generation of the cross between autumnata J^ and filigram- 

 maria $ , the autumnata being of the pale birch type. 



This calls for no special remark ; except in the absence of suffusion, 

 the brood recalls in every way that of similar origin when the birch 

 male was replaced by a pinewood male. 



(2) Hybrids between Oporabia autumnata and O. dilutata. 



Immediately after my discovery of Oporabia autumnata in Wilton 

 pinewood I made preparations for securing the two possible crosses 

 between it and 0. dilutata and to that end reared a large number of 

 pupae of both species which emerged in due time. Unfortunately I 

 had not then realised the highly specialised nature of the pinewood 

 race of 0. autumnata in respect to its time of emergence, for I had con- 

 ceived the idea that in dealing with great numbers some few at least 

 would appear simultaneously with 0. dilutata in October. Such an 

 event, however, did not happen ; without a single exception the autum- 



TABLE VI. 



Summary of sex ratios in the Oporabia autumnata-dilutata experiments. 



Culture Males Females 



Oporabia dilutata. Totals of wild stocks from which parents) „„ „„ 



of hybrids were chosen \ 



Oporabia atitumnata (birch). Totals of three broods from) „- „„ 



which parents of hybrids were chosen \ 



Fi Oporabia dilutata^ X 0. autumnata ^(3 broods) ... ... 52 47 (no ovaries) 



F I Oporabia autumnata ^ xO. dilutata^ (6 broods) ... ... 6 0^ 



nata had long since ceased to emerge when my first dilutata came out. 

 The experiment was therefore a failure. Profiting in the succeeding 

 season from this experience I beat a considerable quantity of wild 

 autumnata larvae in addition to hosts of dilutata from diverse sources 

 and once again provided myself with an abundance of pupae of both 

 species. These preparations ended in complete success for when the 

 first dilutata appeared in October I had both sexes of autumnata caged 

 up. Placing a melanic dilutata female in a cage with autumnata males 

 and vice versa, I confidently awaited results. Almost at once I had the 

 pleasure of seeing ova deposited, and these in every case changed 



1 This result was obtained from over 400 pupae — all males— but which nearly all died 

 as is one's usual experience in this cross. I have reared single females from this crossing 

 in three different broods (otherwise male) in different years ; they were indistinguishable 

 from pure 0. autumnata females. 



