116 U.S. NATIONAL MUSEUM BULLETIN 25 6 



been found at Sanderson, Marathon, and the Davis Mountains. There 

 are very few observations from New Mexico; however, it was prevalent 

 at Ute Park in northeastern corner, and has been taken at Carlsbad in 

 the southeast and at Silver City in the southwest of that State. In 

 Colorado, infested fruit has been located at various points between 

 Trinidad and Boulder, The only record from Utah was made at the 

 Zion National Park near the southern border. 



In Arizona the insect is not abundant except in local areas. In the 

 northern sector it has been met with at Ashfork and Mormon Lake. 

 Most of the records are from southern Arizona, for example, Oracle, 

 Santa Rita Mountains, Santa Catalina Mountains, Baboquivari Moun- 

 tains, and Chiricahua Mountains, where the infestation is often heavy 

 in the foothills and lower mountain valleys, but is, at the most, oc- 

 casional among the extensive fields of prickly pear on the open mesas. 

 In southern California, Asphondylia occurs near Los Angeles, on the 

 coast at Oceanside and San Diego, and in the Cuyamaca Mountains; 

 as in Arizona, the valleys appeared to be favored, and very large fields 

 of Opuntia vaseyi and 0. covillei in exposed situations showed no evidence 

 of its presence. 



In Mexico the midge has been reported from such widely separated 

 localities as Saltillo, in southwestern Coahuila, Aguascalientes, Zaca- 

 tecas, around San Luis Potosi, and in Tehuacan and Oaxaca in the 

 southern highlands. Considering the general abundance of prickly 

 pears, records from the Central Plateau of Mexico are surprisingly few 

 and do not include one locality in the states surrounding Mexcio City. 

 Again, no sign of its existence has been seen in the large areas of Opuntia 

 lindheimeri in the gulf-coast State of Tamaulipas. 



As regards host preference, many species of prickly pears (Platy- 

 opuntias) are known to be attacked, and very occasionally the fruit 

 of certain Cylindropuntias. In the parts of Texas where the insect is 

 most prevalent, the common and often the sole Opuntia is lindheimeri, 

 which is the most general host plant. The related 0. cacanapa is freely 

 infested in the Uvalde district. In the Del Rio sector 0. atrispina and 

 0. phaeacantha types are attacked. In southern Arizona, shrub pears 

 of the 0. engelmannii-phaeacantha group, including 0. discata and 0. 

 Canada, are selected without apparent preference for any particular 

 species. The shrub pears 0. littoralis, 0. vaseyi, and 0. covillei are the 

 host plants in California. Low-growing forms such as 0. tortispina 

 and its relations receive attention in the Dallas-Fort Worth- Austin 

 sector of Texas, in Colorado, and in northern Arizona. In Mexico, 

 the shrub pear 0. cantabrigiensis appears to be preferred to larger 

 plants at San Luis Potosi and Zacatecas, but fruits of tree pears are 

 not immune from attack, the records including 0. streptacantha at 



