455] COLORS OF TIGER BEETLES— SHELFORD 61 



Turning to the scutellaris series one notes that markings are re- 

 duced by high temperature (Figs. 463 a, b,-, 464 a, b, -, PI. XX). The 

 original markings evidently included a middle band like purpurea 

 (Fig. 512, PL XXVIII). As evidence for this note figure 490, plate 

 XXVIII, which shows a reduced band present, and figure 115, plate 

 IX, which shows one in ontogeny which does not persist in the adult 

 at all in individuals from the central states. Stimulation of scutellaris 

 during ontogeny by high temperature merely reduces the markings 

 concentricly, withdrawing the middle band from the margin as well as 

 from the centre. This is the type of modification which has led to 

 immaculate forms in the south and southwest. 



Cold extended the same markings, but the results are not so strik- 

 ing in general plan though perhaps equally general in application, as 

 markings are lost in the same general order in many species if indi- 

 vidual and geographic variation may be used as an indicator. First 

 we have noted that purpurea is divided into two groups, one the steep- 

 bank-inhabiting group and the other the level-ground-inhabitant. The 

 latter (PI. XXV, left, and PI. XXVIII, Fig. 537) loses its markings in 

 the manner suggested above, as indicated by the experimental results 

 with C. tranquebarica. The outer end of the band being lost first. 

 The other loses its markings as does C. scutellaris. Compare 486 to 490 

 with 506 to 510 and 522 to 525, plate XXVIII, which indicate the loss of 

 markings of several species along similar lines, i.e., through retreat to 

 the margin and then reduction of the marginal markings. Thus the 

 response to high temperature represents a tendency present in many 

 species. 



The large confluent markings of Manitoba specimens and of those 

 which have been subjected to cold suggest that a second type of re- 

 sponse may be in the form of a concentric extension of the unpigmented 

 areas. It seems evident that the mechanism in C. scutellaris may be 

 thrown in either direction from the general average of the species. 



I have followed through a series of marking modifications and 

 shown evidence for the tendencies indicated. It would be futile to 

 present further discussions of a similar type regarding other species, 

 as particular weight is given to experimental results and such results 

 are wanting in other species. The reader by an inspection of the 

 figures which are particularly numerous and selected for the purpose 

 will note that in many groups one species begins in pattern modifica- 

 tion where another leaves off. This fact was noted by G. Horn (1892). 

 In many cases an exact knowledge of the geographic variation of the 

 species is not available, but figures 435 to 437, plate XVIII, show a series 

 which is supported geographically. C. curvata which occurs in Mexico 



