40 



EVOLUTION IN COLOR-PATTERN OF THE LADY-BEETLES. 



The presence of this spot is, then, either dominant or preponderant over 

 its absence. 



Spot 2 was also either dominant or preponderant, for where the mates 

 were opposed in this character, presence of the spot in the offspring always 

 prevailed. Inheritance of spot 1 was studied in material from Fairfield, 

 Washington, where it is frequently lacking. Its presence is less strongly 

 inherited than that of the other spots, being found in less than half of the 

 progeny in the case of presence X absence. I believe that this result has 

 a connection with the fact of its frequent absence in that locality. This 

 is in contrast to the inheritance of spots 2 and 6. 



The size of spots is inheritable, as seen in fig. 27, where the unusual 

 proportion in size between 4 and 5 is inherited in some degree. This is 

 conspicuously true of the size of spot 1, where we have, besides the normal 

 center of variation, a second, made up of varieties quinquesignata and 

 caseyi, having the spot large. The shape of spots is also inheritable; thus 

 in fig. 27 the influence of 4 + 6 in one of the parents shows itself in the 

 progeny, though they lack that confluence. 



a o c d e f g 



FIG. 27. Elytral pattern of offspring of 259?. 



The confluence of 4 and 5 is regularly inherited in the heavily pig- 

 mented individuals, especially in the variety quinquesignata. In more 

 lightly pigmented individuals its inheritance is more irregular. It acts 

 as neither a simple dominant nor recessive, yet segregation is evident. The 

 suggestion that a greater degree of pigment is always dominant over a 

 lesser degree does not receive support. 



The confluence of 4 and 6 has neither dominance nor trimorphic heredity. 

 It is segregate,* however, and apparently subponderant. The confluence of 

 -* and 3 is inheritable in various degrees, dependent largely upon the degree 

 of its development. There is segregation with some intermediates, yet the 

 suppositions of dominance or trimorphic inheritance are not tenable. The 

 presence of the extensa character is difficult of analysis, for its presence 

 may be cloaked with excessive pigment. Yet, bearing this in mind, we see 

 that while there is segregation with some intermediates, neither domi- 

 nance nor trimorphic heredity are found. 



*The expression "alternative heredity" is a misnomer in cases where the heterozygptes 

 are intermediate and I therefore prefer the term "segregate heredity." This is divided 

 into amphimorphic heredity, where the two parental conditions are represented in F 2 , 

 and trimorphic, where, in addition, we have a third intermediate condition in F 2 . 



