62 ILLINOIS BIOLOGICAL MONOGRAPHS [456 



is first in the series, dorsalis saulcyi which occurs in Texas next, and 

 dorsalis which occurs in New York and New England shows, spreading 

 of the white. This series is representative of one in which the patterns 

 are of a specialized type, in which the media trachea is reduced. For- 

 ward curves in the humeral lunule are very rare ; one specimen of 

 saulcyi in the collection of Mr. Gestro in Genoa has this marking 

 curved forward. The backward curvature occurs also in trifasciata 

 peruviana but is rare. Figure 434, plate XVIII is probably this 

 species. 



Much detailed study and collecting is necessary to show that the 

 differences which enable one to arrange a group of patterns in series 

 really represent a series geographically or habitudinally separated, and 

 the writer refrains from further discussion of such cases though others 

 might be cited with little doubt as to their validity. The patterns in 

 the illustration pages are arranged to show probable lines of modifica- 

 tion., The large series of parallel trends shown in different groups 

 leaves little doubt that the tendencies shown are highly probable. 



Another tendency quite common in the Cicindelas is the degener- 

 ation of the media trachea. The shifting of the pattern in that region 

 is one of the first modifications to take place if we may judge from the 

 existing patterns and from individual variation. The complete break- 

 ing up of the system of markings appears first in this part of the 

 elytron. This degeneration of the old system of markings has pro- 

 ceeded far in some species such as figure 16, nivea and figure 21, 

 tenuipes. Here an almost entirely new system has grown up, but de- 

 rived from the older one. These cases constitute our best evidence 

 that these patterns are highly specialized. The morphological struc- 

 tures with which the pattern is associated, are modified ; some of the 

 important parts have degenerated. 



In considering these patterns and the modifications which take 

 place the reader must not fail to note that there are physicological 

 problems to be considered and physiological work to be done. The 

 explanation for the occurrence of pigment in some parts of the body 

 and not in others may be very simple. In course of experiments con- 

 cerned with the production of abnormalities, it was found that the 

 labrum which is not pigmented in the species used, develops pigment 

 in the area of wounds. Specimens with abnormal elytra which appear 

 to be due to injury or irritation nearly always have reduced patterns, 

 but no cases in which the white markings are extended are recorded. 

 Thus it appears that the present adult areas of pigmentation and areas 

 of ontogenetic and earlier pigmentation may be merely areas occupied 

 by cells with a higher rate of metabolism. This in the normal elytron 



