21)8 A inia/s Efitonioloi^iral Society of America [Vol. X, 



Conclusions: (1) Bipiinctata-annectans hybrids were formed 

 both in the laboratory and in state of nature. More difficulty 

 was experienced, however, in securing crosses than in the 

 previous experiments with only the native forms, but this may 

 have been partly accidental. They would mate readily enough, 

 but in only comparatively few instances were the eggs affected. 

 The hybrids when formed seemed just as healthy and fertile as 

 the other hybrids. 



(2) Bi piinctata-humeralis hybrids were formed out of doors 

 and these, too, were fertile. 



(3) The appearance of the bi piuictata-aiiucctaus and the 

 bipunctata-hiimeralis hybrids was identical in these cases. 

 Bi punctata dominated completely in the markings of the pro- 

 notum and also in the spots of the elytra unless the smaller 

 size of the spots was a modification. The spots were no smaller 

 though than those that occasionally appeared in what seemed 

 to be pure strains of hi punctata. Evidently in the bipiinctata- 

 annectans hybrid the size of the spot is determined by the 

 marking of the smaller spotted parent, black being recessive 

 in these beetles (see paper of 1911). Except in rare cases the 

 smaller spotted parent is most liable to be annectans. Since 

 bi punctata seems to be small spotted in some cases there is no 

 constantly reliable character whereby to distinguish the hybrid 

 except that it is very likely to be more or less small-spotted. 



Why the size of the spot should be reduced in the bipiinctata- 

 hiimeralis hybrids is far from clear. In these experiments it 

 could hardly have been due to mere fluctuation of the hi punctata 

 element or the results would not have been so constant. For 

 example: In the case of Figure 20, first, third and fourth 

 egg patches 15 hybrids were obtained from the annectans- 

 hiimeralis female crossed with a bipunctata male. The chances 

 are that half of these were bipiinctata-annectans and half were 

 bipunctata-humeraUs hybrids, which should be enough to show 

 some variation, but the dot seems to be of practically uniform 

 size in all. 



(4) Bipunctata, in the hybrid form, was reared from the 

 same patch of eggs as were also melanopleura and coloradensis, 

 and this seems very good if not indeed, conclusive evidence 

 that they are able to interbreed with these forms too, though 

 the exact hybrids were not all produced. 



