210 GENUS ARENIVAGA (bLATTIDAE) 



Arenivaga tonkawa'" new species (Plate VII, figures 8 and 9) 



1902. Homocogamia boViana Rehn, (not of Saussure, 1893), Trans. Am. 

 Ent. Soc, xxvii, p. 331. [d^; Round Mountain, Texas.] 



1903. Homoeogamia holliana Rehn, (not of Saussure, 1893), Proc. Acad. 

 Nat. Sci. Phila., 1903, p. 187. [cf ; Austin and Round Mountain, Texas.] 



1917. Arenivaga erratica Hebard, (in part, not of Rehn, 1903), Mem. Am. 

 Ent. Soc, 2, p. 231, pi. ix, fig. 13. [cf , 9 ; Waco, Bosque County, Ballinger, 

 Shovel Mountain in Burnet County, Austin, Round Mountain, George- 

 town, Goliad, Brownsville, Kerrville, San Antonio, Cotulla, Esperanza 

 Ranch near Brownsville, Sabinal, Knippa, Carrizo Springs, Ringgold 

 Barracks near Rio Grande, Devils River, Texas.] 



Tlie present species is very closely related to crralica, replacing 

 that species east of the Pecos River in Texas, in which territory 

 it is distributed through the semi-arid area from Waco south to 

 Brownsville. 



No indication of intergradation is shown, specimens from the 

 Big Bend region of the Rio Grande being typical of erratica 

 and those from east of the Pecos typical of tonkawa. 



Were either of these species constant in the features usually 

 employed for specific separation, our previous assignment would 

 be reprehensible. We find, however, that in all usually rclial)le 

 external structural characters a decided amount of variation 

 occurs, tonkawa being distinguished readily and, as far as we 

 can see, only, by the distinctive form of the concealed dextro- 

 ventral genital plate in the male sex. Though some variation 

 occurs in the form of this plate (see plate VII, figures 8 and 9), 

 the general character remains the same and is very distinct from 

 the type developed in erratica. 



Unfortunately, the greatly sim])lified female sex appears to 

 have no structural differences liy which it can be separatctl from 

 that sex of erratica. No difficulty is experienced in assigning 

 females, however, as this species and holliana are the only forms 

 of the genus Arenivaga which occur in Texas east of the Pecos 

 River; females of holliana being readily separated by their sub- 

 orbicular form, blackish general coloration and av(>rag(> much 

 larger size. 



Tyj)e. — cf; Carrizo Springs, Dinmiit County, Texas. (A. 

 Wadgymar.) [Hebai'd Collection, Type no. 581.] 



^" The Tonkawa Indians once inhabited the region where this species occurs. 



