435] COLORS OF TIGER BEETLES— SHELFORD 41 



extreme forms are comparatively rare and confined to the Pacific states. 

 Plate XXI shows the classes into which the patterns of this species may 

 be divided and their distribution. The graphs represent the distribu- 

 tion of the per cent of classes shown by the figures below for specific 

 localities. It will be noted that types g and h which correspond in 

 middle band characters occur occasionally as extremes especially in 

 Kansas and Texas localities, while west of the rockies where the summer 

 and springs are dry and favor high soil temperatures these types are 

 fairly common. This type of marking with middle band reduced at 

 the margin makes up a considerable percentage of the individuals 

 collected at Hagerman, Idaho ; San Bernardino, California ; Provo, Utah ; 

 and Las Vegas, Nevada ; but they are nowhere the dominant type. In 

 certain Nevada localities the retirement of the middle band appears 

 to begin at the inner end and the withdrawal from the margin follows 

 only in very reduced types. The type with the middle band with- 

 drawn occurs in southern and western localities. Twelve per cent of the 

 specimens from central Texas show middle bands like those modified 

 in experiment. On the whole there is a correspondence between high 

 soil temperature and the reduced type of markings which accords with 

 the experimental results. 



Plate XXIII shows the geographic variation of C. scutellaris and 

 its varieties ranked as aberrations by Horn. The series of classes shown 

 beginning at the extreme left are from the northern portion of its 

 range in New England ; passing to the right are shown very reduced 

 markings at Raleigh, and very rarely any markings at all at Mobile 

 and in Texas localities or points in western and west central states : 

 Oklahoma, Kansas, Nebraska, and South Dakota, Colorado and New 

 Mexico. In all localities, however, on and east of the Missouri River 

 in the central states, there is a noticeable increasing in the size of mark- 

 ings as we pass to more northerly localities and to more easterly local- 

 ities as far 1 as Chicago. East of Chicago the marking of specimens 

 from along the lake shores are not larger than those taken at the south 

 end of Lake Michigan. As will be seen from the graphs (PL XXIII) 

 the range of variation is least in the gulf states localities where the 

 markings are most reduced. 



There is further a noteworthy difference in the Mississippi Valley 

 and Atlantic Coast forms. The humeral dot {ai, Fig. 48, PI. V) is 

 never present and the so-called posthumeral dot (A2.3, Fig. 48, PL V) 

 is seldom so except in the more northern localities and is never large 

 when present. It is never joined to the middle band {A4, B4). The 

 markings are massed in the posterior half of the elytron on the costal 

 margin. In the forms from Missouri River localities and eastward the 

 humeral dot is usually present — always present in the more eastern 



