COLOR AND COLORATION 189 



this variation in this species is partially indicated in Fig. 240, and that 

 of Cicindela in Fig. 241. 



Individuals of Cicindela vary in pattern in a few definite directions, 

 and the patterns that characterize the various species appear to be 

 fixations of individual variations. According to Dr. G. H. Horn: (i) 

 The type of marking is the same in all our species. (2) Assuming a well- 

 marked species, tranquebarica (vulgaris, Fig. 241, 7) as a central type, 

 the markings of other species vary from that type, (a) by a progressive 

 spreading of the white, (b) by a gradual thinning or absorption of the 

 white, (c) by a fragmentation of the markings, (d) by linear supplemen- 

 tary extension. (3) Many species are practially invariable (i.e., the 

 individual variations are small in amount as compared with those in 

 other species) . These fall into two series : (a) those of the normal type, 

 as tranquebarica, hirticollis and tenuisignata; (b) those in which some 

 modification of the type has become permanent, probably through 

 isolation, as marginipennis, togata and lemniscata. (4) Those species 

 which vary do so in one direction only. New types of pattern, of 

 specific value, appear to have arisen by the isolation and perpetuation 

 of individual variations. 



Professor Shelford, in his important monograph on the colors of 

 these beetles, draws the following conclusions, among others: 



Longitudinal stripes in which pigment usually occurs lie in the area 

 of the chief tracheal trunks of the elytron; there are seven cross bands in 

 which pigment does not develop; the second and third and fifth and 

 sixth of these are often joined to make one of each pair. 



Pigment usually occurs about the bases of hairs, which usually lie 

 in the lines of the tracheae. 



In ontogeny the elytra show a spotted condition corresponding to the 

 system of cross bands and longitudinal stripes. The longitudinal 

 stripes are usually more pronounced. 



The characteristic markings of the group are composed of spots or 

 elements joined in the longitudinal light stripe areas and areas of cross 

 bands, with the loss of various spots or elements which occur in onto- 

 geny; joinings are sometimes oblique, and when so markings are some- 

 times, parallel with the curved end of the elytron. 



Certain particular types of markings made up of a few elements joined 

 in a particular way characterize the majority of species of the group. 



These markings as derived from the cross and longitudinal bands are 

 angular; reduction of angles, straightening and turning into oblique 



