CACTUS-FEEDING INSECTS AND MITES 133 



gether, but hundreds will congregate on one small prickly pear joint. 

 The social habit and the concentrated attack on the joints make this 

 species a more destructive insect than C. tabulate. 



The host plants of C. vittiger Uhler include most, if not all, species 

 of Platyopuntia growing within its range of distribution. These em- 

 brace the shrub pears (0. lindheimeri and inermis in Texas; 0. dillenii 

 in Florida; 0. discata, phaeacantha, and engelmannii forms in western 

 Texas to Arizona; and 0. occidentalis in California), and the dwarf 

 pears (0. lata in Florida; 0. tortispina and polyacantha forms in North 

 Texas to Idaho; and 0. basilaris in California). More rarely, Cylindro- 

 puntias are attacked: the Board's records include 0. leptocaulis in 

 Texas; 0. imbricata in West Texas and New Mexico; and 0. bernardina, 

 serpentina^ and echinocarpa in California. 



The fecundity compares with that of 0. tabulata. In Australia the 

 greatest number of eggs from one female was 230; this female laid 

 freely during October and November and deposited a few eggs in 

 February and March. Another individual laid 220 eggs in 27 separate 

 lots in January and February. 



The incubation period varies with the time of year. The shortest 

 duration of the egg stage recorded in Australia and Texas was 9 days. 

 Hunter, Pratt, and Mitchell (1912) give periods for each larval instar 

 which total 41 days for larval development; Hamlin's (1924) figures 

 make a total of 53 days for the larval period. In Australia larval develop- 

 ment occupied 40-59 days in October and Novem^ber, the life cycle 

 taking 53-73 days. In January-March, the larval period occupied 

 54-67 days, and the life cycle 66-79 days as follows: 



Under similar conditions the development of C. tabulata was less rapid, 

 occupying 57-90 days for the larval stages and 67-100 days for the 

 whole life cycle. 



NARNIA Stal 

 The several species are primarily fruit feeders, although they will 

 attack prickly pear joints. We have not been able to recognize N. 

 inornata Distant, but believe that records of this species in the United 

 States and Mexico refer to JV". pallidicornis StSl. 



