130 U.S. NATIONAL MUSEUM BULLETIN 256 



tains and the movmtainous sections of Brewster and Presidio counties 

 in the Big Bend country, and at the Devil's River, west of Del Rio. 

 The adult C. canyona can be distinguished without difficulty from the 

 typical form of C. tabulata occurring at lower elevations. The ground 

 color has a red tinge, the elytra are shaded black, the legs are smoky 

 basally, and underneath the body the light-yellow abdomen contrasts 

 with the dark thorax. Nevertheless, doubt may be expressed with 

 regard to the specific distinction of C. canyona. There is some evidence 

 that it is merely a variety or geographic race of the widely distributed 

 C. tabulata. For instance : 



Dark forms of C. tabulata: occur at various points in Mexico. 

 Examples from Durango and Parral (Chihuahua) are not only dark 

 but possess the red tint of C. canyona; in fact, they could be referred to 

 either species. 



C. vittiger and C. tabulata are variable species, according to locality; 

 two quite distinct color varieties of C. vittiger occur within 50 miles 

 of each other. 



The taxonomic characters used to separate canyona, namely, the 

 number of teeth on the femora and the relative length of the juga and 

 tylus, appear to be variable. 



In Australian experiments C. canyona and C. tabulata interbred 

 very readily; the hybrid progeny were fertile and were bred through 

 several successive generations. 



If C. canyona is merely a variety or race of C, tabulata, an explanation 

 is necessary to account for the occurrence of the two forms within 20 

 miles of each other. The typical C. tabulata occurring from Brownsville 

 to Uvalde is obviously a coastal form that has spread northward from 

 the lower elevations of Mexico through the States of Tamaulipas and 

 Nuevo Leon. In view of the similarity in color between the Durango 

 and Parral specimens of C. tabulata and C. canyona, it would seem 

 reasonable to consider that a western or mountainous form or race of 

 C. tabulata has spread northward along the western edge of the Mexican 

 plateau through Durango and Chihuahua to enter Texas by way of 

 the mountains of the Big Bend. 



C. canyona attacks Platyopuntias such as 0. lindheimeri, 0. cacanapa, 

 and 0. engelmannii-phaeacantha types. Bennett (1963, unpublished report) 

 records it on 0. megacanlha and 0. streptacantha. Hamlin (1924) records 

 Echinocereus as a host plant. In Australia 0. inermis and 0. stricta proved 

 suitable food plants. 



The life history and habits are similar to those of C. tabulata, except 

 in certain particulars. Adults have been observed in Texas in all months 

 of the year. Both in Australia and in cages at Uvalde they became 

 active and oviposited earlier in the spring than either C. tabulata or 



