CACTUS-FEEDING INSECTS AND MITES 33 



extremely abundant. The host plants are the low-growing prickly 

 pears 0. tortispina, 0. polyacantha, O.fragilis, and their relations. Efforts 

 at Uvalde, Texas, to rear the larvae in the bushy 0. lindheimeri and 

 0. atrispina were unsuccessful; however, in Australia this insect 

 completed its life cycle on 0. inermis and 0. stricta. 



The larvae cause serious injury to the low-growing prickly pears. 

 Individual plants are destroyed completely, and whole fields of Opuntia 

 tortispina and 0. polyacantha are severely damaged. As they develop, 

 the colonies of larvae tunnel through the plant and split up into 

 smaller groups, so that it is not uncommon to find not more than 

 two or three large larvae in each attacked segment. Since the larvae 

 crawl considerable distances at pupation time, tlie cocoons are not 

 readily located in numbers, even in areas where tlie insect is prevalent. 



There is one generation annually. Pupation occurs in June and 

 July, and moth emergence in July and August. In late June and 

 early July 1926 the life cycle was more advanced on the western 

 than on the eastern side of the Rocky Mountain system; thus, in 

 Kansas, eastern Colorado, and Wyoming the larvae were not full 

 grown, whereas in Idaho and Utah all larvae had pupated. In 1925 

 moths from northern Arizona emerged during the period July 6 to 18, 

 and those from eastern Colorado from August 21 to 31. The following 

 year, moths from eastern Colorado emerged from July 30 to August 30. 

 Probably the females are capable of laying as many as 200 eggs. 

 The following records were obtained from various lots of material: 



The eggsticks contain an average number of 30 to 40 eggs; the 

 highest record has been a stick of 92 eggs. An incubation period 

 of 9 days was obtained at Uvalde, Texas, in July. 

 Parasites. — The following natural enemies have been bred from the 

 pupal stage: The tachinids Phorocera texana and P. comstocki, the chalcid 

 Brachymeria {Pseudobrachymeria) pedalis, the ichneumon Trichomma sp., 

 and an undetermined braconid. 



Melitara doddalis Dyar 



Heinrich (1956) places this as a synonym of M. dentata Grote; this 

 form, however, which was described in 1925 from material collected 

 at Mesilla Park, New Mexico, has a wide distribution from the plateau 



263-417—68 1 



