844 



SCIENCE 



[N. S. Vol. XXXII. No. 832 



conditions. A progressive change from one 

 condition to another was noted and the ques- 

 tion was asked if this change were not an 

 example of determinate variation. The 

 other possible explanations, i. e., natural se- 

 lection and temporary ontogenic modification, 

 were considered and held to be inapplicable. 



I have continued the annual inspection of 

 the color pattern status of the beetle since 1905 

 and present in the following notes the results 

 of the observations of the last five years 

 (1905-10). In order to make reference to the 

 earlier paper unnecessary to hurried readers 

 I resume in this the data of the 1895-1905 ob- 

 servations and repeat two or three para- 

 graphs of explanation. 



The beetle Diahrotica soror is a chrysome- 

 lid species that infests our California flower 

 gardens. 



In its larval stage, this beetle lives as a 

 slender white grub underground, feeding on 

 the roots of aKalfa, chrysanthemum and 

 various other plants. It pupates in a small 

 subterranean cell near the surface and the 

 adult beetle, on issuance from the pupal 

 cuticle, makes its way above ground and feeds 

 on the buds and open flowers of roses, chry- 

 santhemums and almost any other of Cali- 

 fornia's favorite blossoms. The color pattern 

 of the adult is, of course (as the insect is one 

 of "complete metamorphosis"), definitive and 

 fixed as to both pattern and color at the time 

 of the first appearance of the adult above 

 ground. 



This beetle has its black and green colors 

 arranged on its back (dorsal surfaces of the 

 wing-covers) in the form of twelve distinct 

 black blotches or spots on a green ground, six 

 spots in three transverse pairs (or two longi- 

 tudinal rows) on each wing-cover. At least 

 the original description of this species gives 

 this patterning, and systematic accounts and 

 revisions of the genus have always ascribed 

 to the species soror twelve separate black 

 blotches on a green (or yellow-green) ground. 

 In Horn's revision of the genus in 1893' the 

 fact of a tendency of the black spots to coa- 

 lesce is fleetingly referred to. But undoubt- 



- Trams. Amer. Ent. Soc. V., 20, p. 89 ff. 



edly the twelve-free spots type is the pattern 

 which is accepted as the typical and usual 

 one. 



The pattern variation is shown (by select- 

 ing certain principal types appreciably dis- 

 tinct) in Fig. 1, where A represents the con- 

 dition accepted by the systematists as typical 

 of the species (both right and left elytra are 

 shown) ; B shows the two spots of the middle 

 transverse pair of the left wing-cover fused; 



Fig. 1. Diagrammatic representation of the 

 varying elytral color pattern of the California 

 flower beetle, Diahrotica soror. (The ground color 

 is green; the spots are black.) 



C, the corresponding two spots of the right 

 wing-cover fused; Z), the two spots of the pos- 

 terior transverse pair of the left wing-cover 

 fused; E, the corresponding spots of the right 

 wing-cover fused; F, the longitudinal fusing 

 of the spots on the left wing-cover, and G, 

 the corresponding condition for the right 

 wing-cover. 



These different patterns are closely con- 

 nected by intergrading conditions; that is, 

 there may be (theoretically) and are (actu- 

 ally) all degrees of fusion of the two spots in 

 these various pairs that show fusion at all, 

 from the slightest running together to the 

 more pronounced cases shown by the dia- 

 gram. But for the sake of aggregating indi- 

 viduals into describable groups any fusion is 

 called fusion, and the existence of even the 

 slightest space or line of green between two 

 spots is recognized as " no fusion " or " free 



