CACTUS-FEEDING INSECTS AND MITES 135 



the middle of May to early August, and develop to adults in August to 

 early October. Thus the life cycle occupies about 2 months. Our 

 records do not give the duration of the incubation period or of most of 

 the larval instars. Hunter, Pratt, and Mitchell (1912) record 27 days 

 for the incubation period and 39 days for development of the larvae. 

 The duration of the first instar is brief; observations at Uvalde, Texas, 

 give 4 days in April and 2-3 days in August, and 7 days for the second 

 in the latter month. 



Parasites. — Two parasites are known. The tachinid Trichopoda 

 pennipes attacks the adults and larvae. At Uvalde the egg parasite 

 Hadronotus atriscapus was reared in August 1923 and 1924. 



Namia snowi Van Du2ee 



The distribution of this form appears to be restricted to the United 

 States, extending from western Texas, through New Mexico as far 

 north as southern Colorado, and across southern Arizona to southern 

 California. 



In western Texas it has been observed commonly in the Davis 

 Mountains, at Alpine, Brewster County, and at Presidio on the Rio 

 Grande. Records from New Mexico include Carlsbad and Albuquer- 

 que. In July 1925 the species was abundant at Trinidad in southern 

 Colorado. It is not uncommon in the Tucson district of Arizona as 

 far west as the Quijotoa Mountains. In soudiern California it was 

 prevalent in June 1925 at San Felipe on the eastern slopes of the 

 Cuyamaca Mountains. 



The host plants include both Platyopuntias and Cylindropuntias; 

 and the attack seems to be restricted to the fruit. In June-July 1924 

 the food plant in west Texas and New Mexico was invariably the 

 Cylindropuntia 0. imbricata, whereas in the Tucson district the bugs 

 were feeding on the fruit of Platyopuntias only (0. engelmannii and 0. 

 phaeacaniha forms) although Cylindropuntias were more abundant. 

 At Alpine, Texas, in August 1924 they were plentiful on 0. imbricata 

 and sparse on the Platyopuntia 0. macrocentra. In the Cuyamaca Moun- 

 tains, California, in June 1925 both prickly pears 0. covillei and 0. 

 vaseyi and Cylindropuntias 0. serpentina and 0. bernardina were attacked. 

 Under cage conditions at Uvalde, Texas, they attacked both 0. 

 imbricata and 0. lindheimeri without appreciable destruction. 



Our information on the life history is most incomplete. It is not 

 known whether one or two generations occur annually. Eggs were laid 

 in June and July, and the larvae reached maturity in August-October. 

 The life-cycle occupied about two months. A stock of 90 adults in 

 June had increased to 2,000 adults and large nymphs by September. 



