242 NORTH AMERICAN BLATTIDAE 



i\s in the species of Arenivaga, the size variation in this insect 

 appears to be wholly attributable to local environmental factors. 



Coloration. — cf . In the maximum intensive type of coloration 

 the pronotum has the cephalic margin pale, this narrowest in the 

 brief mesal portion, on each side of which an invasion into the dark 

 brown of the remaining portion of the pronotum is weakly indi- 

 cated. In one of the darkest specimens before us, the pronotum 

 has two large latero-caudal blotches of vinaceous rufous. In 

 such dark material, the tegmina and wings are also darkened, but 

 not maculate, nor is their transparency lessened. The material 

 before us shows varied gradations from this type to the maximum 

 of recessive coloration, in which the entire insect is light buff, the 

 pronotum clouded latero-caudad with ochraceous-buff. 



9 . Mars brown or russet above, heavily clothed with ochra- 

 ceous-buff hairs. 



The insect is apparently to be found in its greatest abundance 

 in the extreme desert condition of the Southwest. Dr. Wheeler 

 found males flying across the desert in small swarms on March 

 10, 191 1, at Yuma, Arizona; all of the material seen by us was like- 

 wise of the male sex, attracted to lights at night. 



Specimens Examined: 29; 25 males and 4 females. 



Albuquerque, New Me.xico, VI, 22 and VIII, 7, 1912, (Merrill), i cf', i 9, [Somes 

 Cln.]. 



Las Cruces, N. M., (T. D. A. Cockerel!; at light), i d^, type; (T. D. A. Cockerel!), 

 I 9, [both M. C. Z.]. 



Alamogordo, N. M., IV, li to VI, 6, 1902, (Rehn and Viereck; majority at light), 

 ;8 cf, [A. N. S. P. and Hebard Cln.]. 



Mesilla Park, N. M., I, 1900, (C. Thompson), i 9 , [U. S. N. M.]; (C. N. Ainslie), 

 1 9, [Hebard Cln.]. 



Las Vegas, Nevada, 2050 feet, VIII, 9, 1907, (Hebard; at light). 2 o^. [Hel:)ard 

 Cln.]. 



Maricopa Divide, Maricopa County, Arizona, X, 2, 1910, (Hebard; attracted to 

 ligkt on train), 2 cT, [Hebard Cln.]. 



