November 16, 1906.] 



SCIENCE. 



627 



bird or insect is going to distinguish between 

 beetle A and beetle B by the middle-spots-free 

 or middle-spots-fused criterion. Eor one, I 

 am done with meekly accepting the dictum of 

 the selection champions who declare, in such 

 cases as the present one, that we do not know 

 what difference in general effect of harmony 

 with leaf or flower or what not, and hence 

 with the safety of the beetle, a very slight 

 modification of pattern may produce; that we 

 can not say of any difference, however minute, 

 or apparently indifferent, that it is not the 

 hair in the balance; and that when we under- 

 stand all the conditions of the life of an or- 



Fig. 8. Frequency polygon of the variation in 

 elytral pattern of 405 specimens of the Cali- 

 fornia flower beetle, Diahrotica soror, collected 

 at Santa Rosa, California, about sixty miles north 

 of the Stanford University campus, October, 1902. 



ganism, then, and only then, are we entitled 

 to say of this or that character that it is not 

 of lif e-and-death value. When we accept such 

 a dictum we put aside all need of study, all 

 spur to work, for ' all the conditions ' is a 

 phrase to crush with. However, there are but 

 few selectionists left who insist any longer on 

 taking this point of view. Practically all 

 Neo-Darwinians admit the existence of hosts 

 of trifling, insignificant, indifferent species 

 and variety characters. As for those who still 

 hold to their crushing dictum — well, we can 

 simply refuse to crush. 



In the particular instance before us, har- 

 mony of the color pattern of our beetle with 

 its environment is out of the question. In 

 fact, the glaring disharmony of the chrysome- 

 lid beetles with their habitual green leaf en- 

 vironment has been long notorious and has 

 offered them a general card of admission to 

 the group, probably not wholly fanciful, of 

 ' aposematically ' patterned animals, that is, 

 creatures of malodor or distaste to their verte- 

 brate enemies and conspicuously colored to 

 warn these enemies of the malease which 

 gastronomic attention to them will produce. 

 So that the selective value of two-spots-fused 

 or two-spots-free is that of helping make the 

 pattern a distinct and readily perceived one. 

 Now throughout the whole great family of 

 Chrysomelid beetles the prevailing patterns 

 are stripes, longitudinal or transverse, spots, 

 and a clear ground color with neither spots 

 nor stripes. In genus after genus in this 

 family these three types of patterning are all 

 represented by species of apparently equal 

 abundance, vigor and general success in 

 making life a burden to the horticulturalist 

 and farmer. And these species with their 

 different pattern types may, and often do, live 

 side by side. Precisely in the genus Dia- 

 'brotica is this interesting condition of things 

 excellently exemplified. In the Mississippi 

 Valley Diahrotica longicornis, with its unpat- 

 terned blue back, eats the sweet corn of the 

 truck farmer, while the longitudinally black- 

 striped D. vittata eats his cucumbers and 

 melons, and the yellow D. 12-punctata, with 

 its twelve separate black spots, attends to the 

 rest of the truck. Here in California we are 

 able to distinguish D. soror from 12-punctata 

 which ranges up to us from the middle west 

 and great southwest only by the fact, quite 

 sufficient for systematic coleopterologists, that 

 the under side of thorax and abdomen and the 

 bases of the legs (all parts well out of sight 

 of preying lizard or bird) are strongly dusky 

 instead of yellow. The exposed dorsal color 

 pattern is the same in both. So that the 

 differentiation of these two species was cer- 

 tainly never brought about by any selection of 

 protective warning color-pattern variations. 



