CACTUS-FEEDING INSECTS AND MITES 5 



The cochineal coccids Dactylopius Costa are confined to Opuntia and 

 the closely related genus Nopalea. One species, D. newsteadi Cockerell, 

 would appear to be limited to Cylindropuntia hosts, but the others 

 are prickly pear enemies, since the Nopalea food plants are typical 

 prickly pears. 



Although many cactus insects in the United States and Mexico 

 attack both Platyopuntias and Cylindropuntia s, the latter group has 

 a distinct insect complex. From western Texas to California, three 

 insects, the moth borers Cahela ponderosella (Barnes & McDunnough) 

 and Alberada parabates (Dyar) and tlie cerambycid Coenopaeus palmeri 

 (LeConte), are associated with various plants of this type, including 

 0. imbricata in western Texas and New Mexico, O.fulgida in Arizona, 

 and 0. prolifera and 0. echinocarpa in California. Attempts to rear the 

 two phycitids on prickly pears were unsuccessful, but occasional 

 examples of Coenopaeus palmeri (LeConte) were bred on these plants 

 in cages. Chelinidea hiinteri Hamlin in southern Arizona appears to be 

 restricted to the cylindrical forms. The two moth borers Cactoblastis 

 jnundelli Heinrich and Nanaia substituta Heinrich attacking the Peruvian 

 Cylindropuntia 0. exaltata were not found associated with prickly pears. 



The slender-jointed Cylindropuntia 0. leptocaulis of Texas and ad- 

 jacent districts in Mexico possesses four distinct insect enemies: the 

 moth borers Albdrada holochlora (Dyar) and Rumatha glaucatella (Hulst), 

 the weevil Gerslaeckeria clathrata (LeConte), and the fiea beede Di- 

 sonycha varicornis Horn. However, as tliis plant usually occurs in areas 

 where other Cylindropuntias are absent, the restriction to one host 

 is not definitely established. 



In addition to host restriction, there is considerable host preference, 

 or perhaps host adaptability, to be discussed in more detail later. Thus, 

 the bugs Chelinidea vittiger Uhler and Narnia snowi Van Duzee occur 

 in New Mexico and Arizona, where various Platyopuntias and Cylin- 

 dropuntias are common plants; C. vittiger Uhler is rarely found on the 

 cylindrical forms, while JV. snowi Van Duzee obviously prefers the 

 fruit of these plants. The seed midge Asphondylia opuntiae Felt attacks a 

 great many species of prickly pear; it has been reared on occasion from 

 Cylindropuntia fruit in Texas and Mexico but not in Arizona, where 

 heavy infestations have frequently been encountered in prickly pears. 



In Argentina, Cactoblastis cactorum (Berg) has been recorded from 

 many prickly pear hosts of varying types of growth, but it has not been 

 recorded as an enemy of the very common prickly pear 0. sulphur ea. 

 On the other hand, 0. sulphur ea is the usual host of the closely related 

 Cactoblastis doddi Heinrich, which has not been encountered attacking 

 such normal hosts of C. cactorum (Berg) as Opuntia utkilio and 0. discolor. 

 Host preference is very marked among the cochineals Dactylobius 



