HIPPODAMIA. 



37 



MODIFICATION. 



Subjection of the prepupa and pupa to an ordinary poultry incubator at 

 40 C. resulted in no appreciable modification, nor did increase or decrease 

 in humidity. But an increase of 

 pigment was obtained by expos- 

 ing the prepupa and pupa to the 

 cold of a refrigerator (5 to 15 

 C.), a cellar (15 to 17 C.), and 

 the intermittent temperature of 

 an ordinary room where the 

 temperature dropped during the 

 winter months from 12 to 18 C. 

 by day to 5 C. at night. The 

 greatest degree of pigmentation 

 resulted in the last case. The 

 result from one experiment, in 

 which the prepupa 3 of typical 

 Hippodamia convergens were 

 subjected to a freezing tempera- <> Diameter of spot 3. / 

 ture out of doors for two nights, ( ( ^ ^envu^ 

 was the elytral pattern shown in <</) AH individuals, 

 fig. 25, which is much like that of 

 the western mountain beetles. 

 The other cases give the prono- 

 tum that is so frequently found 

 in the western beetles, but elytra 

 not corresponding to any known 

 variety. Fig. 26 is a composite 

 drawing, no one beetle showing (<o~o 

 the same high degree of pigmen- |'!j 0034 

 tation at every point. Some f ea- ( ' ~ 5 5 



tUreS Of this modification pattern y iri . i?.-varlation of the diameter of spof_ iii ///>/'"- 



show a correspondence to some 



of the varieties in nature ; other features are produced only by artificial 

 modification, especially the pigment line between 1 and 4, which is not 

 the same as the vitta in Hippodamia spuria var. or H. apicalis var. 



HEREDITY. 



Every variety or noticeable variation which has been tested is inher- 

 itable in some degree. Even though the variety has been brought from a 

 different region, it has maintained itself in our vivarium. 



The heredity of spot 1+3 shows a nearly perfect segregation. There 

 is a lower degree of segregation in the confluence of 4 and 5. The closest 

 approach to blended inheritance is in the size of the pronotal dash and the 

 incomplete lateral margin of the pronotum. Yet in each of these cases it 





1 2 3 



4 5 



3 3 



3 3 

 G 



G 7 8 9 10 11 12 13 



G 11 8 7 7 4 1 = 55 



5 8 17 13 5 3 = 03 



5 11 19 25 20 12 7 1 = 113 



