399] COLORS OF TIGER BEETLES—SHELF ORD 



INTRODUCTION 



In the analysis of characters made the basis of studies of variation, 

 orthogeuetie trends, experimental modification and heredity, noteworthy 

 advantages are associated with the study of large groups of species 

 in which divergence and modification have proceeded in various direc- 

 tions. The material should be plastic so that the laws governing 

 response in characters can be determined. The ontogeny of the char- 

 acters should be of such a character as to show the general ground 

 plan of the system and its relation to the existing adult characters and 

 their variations. It is further desirable to be able to breed the organ- 

 ism, segregate pure lines, and cross various species. There is a strong 

 tendenej' of late years to regard the breeding and the breeding results 

 as superior to the other attempts at character analj'sis. This has pro- 

 ceeded to such an extent without adequate physiological analysis that 

 one writer (Riddle, 1909) designated the method of cross breeding "the 

 mixing of unknowns". The primary object of this paper is to show 

 the nature of the color and color-pattern mechanism of the elytron. 



In the matter of qualifications of material the tiger beetles are 

 admirably adapted to all the needs enumerated above, but since one 

 year at least and normally two are necessary for a generation, only 

 a few single generations have been bred. For this reason the idea of 

 breeding them was abandoned. It is also a purpose of this paper to- 

 show that breeding is not the only method by which adequate analysis 

 can be reached, i.e., unless the laws governing heredity are a system 

 entirely a part from those governing the modification of parts during 

 ontogeny and the normal course of A'ariation, which seems to be the- 

 tacit assumption of various students of heredity in the not too distant 

 past. 



I shall indicate further that orthogenetic tendencies, if directive 

 tendencies are to be so named, are numerous and in a large series of 

 species present a confusing set of groups wliieh are excessively com- 

 plicated and reduced to any simple system, as claimed bj^ Eimer and 

 von Linden for Lepidoptera or for a limited number of species by 

 Wlntman, with difficulty. Still, large tendencies with numerous minor 

 ones within them may be detected. It will be shown that the laws 

 governing the modification of patterns apply alike to general, probably 

 liereditary tc.'^deiicies a;ii! det:;il''d r,:.spc:t y.i under e.\j*:'rijii.':iiKl co;)- 



