REVISION MALACOSOMA HUBNER IN NORTH AMERICA 63 



A sample of males from the Fj rearings R27, R28, R35, and R36 

 showed the prongs of the accessory claspers to be more or less inter- 

 mediate, but with more of them tending toward the lutescens type, and 

 with much variability. A similar sample of females showed that most 

 of them were between the range of figures 98 and 101, but as in the 

 case of the males, they tended to be closer to the lutescens type. The 

 genital plate of most female lutescens from collections 173 and 179 was 

 more extensively sclerotized than the genital plate of most female 

 pluviale from collection 180, in which it was almost totally unsclerotized. 

 In the sample of Fi females, nearly all of them had genital plates 

 which were more extensively sclerotized than the parent pluviale 

 females. 



Some characters of the Fi specimens show greater variability than 

 either parent, some are more or less intermediate, and others tend to 

 dominate. Similar results were obtained in the other Fj rearings. 

 These observations on only a few easily seen characters show that 

 neither parent is dominant over the other. The best explanation for 

 the distinctive combinations of characters shown by typical lutescens 

 and pluviale is that they provide some selective advantage over other 

 combinations in the areas where they are found. 



The data presented above for lutescens and pluviale are not conclusive, 

 but they suggest the possibility that some genetic isolation exists 

 between the males of lutescens and females of pluviale in the Canadian 

 part of their distribution. This does not appear to be present when 

 the reciprocal mating takes place. Further investigation should be 

 done on this subject, however, since these results could have been 

 caused by peculiarities of the local populations which were used, rather 

 than attributes of the entire populations of lutescens and pluviale. Despite 

 this possibility and despite differences in some larval and adult charac- 

 ters, these two populations are regarded as subspecies of Af. calif ornicum, 

 because, as far as is known, all of these differences break down and the 

 populations intergrade completely with each other and with the central 

 populations of M. californicum along the western edge of the Great 

 Plains in the northern United States (see figs. 377-379 and compare 

 with figs. 370-372, figs. 373-376, and figs. 383-387). 



F2 Egg Masses 



F2 egg masses were obtained from the 1960 Fi whenever possible, 

 but, as previously noted, survival was very poor, so they were not 

 satisfactorily reared. A sample of 20 eggs was examined from each egg 



