CACTUS-FEEDING INSECTS AND MITES 41 



pears occurring within its region of distribution. The host plants in 

 west Texas to Arizona are the shrub plants Opuntia engelmannii, 0. 

 phaeacantha, and their many related forms; the iong-spined 0. macro- 

 centra of west Texas and New Mexico is especially favored, while in 

 the foothills country of the Pecos River, 0. atrispina receives attention. 

 In northern Arizona, Colorado, Kansas, Nebraska, and Wyoming, 

 low-growing prickly pears of the 0. tortispina and 0. polyacantha groups 

 are attacked freely; in southern Utah 0. basilaris has been recorded 

 as a food plant. 



The moths are darker and rather smaller than those of Olycella 

 iunctolineella. The larvae are banded with a light purple instead of 

 deep blue or black, and often the color is so pale as to appear almost 

 wholly white. 



Apparendy there is one annual generation. The larvae spin cocoons 

 from September to November; winter is spent in the pupal stage and the 

 moths emerge from March to May. 0. subumbrella Dyar is the only 

 cactus phycitid known to overwinter in the pupal stage. However in 

 rearing cages at Uvalde, Texas, which has a lower elevation than the 

 region of distribution in western Texas, larvae pupated in late Septem- 

 ber from eggs deposited in April and May; instead of remaining in the 

 pupal stage during winter, adults emerged in October and laid eggs 

 which hatched at tlie end of the same month. 



Fecundity is comparatively high; thus, 17 females deposited an aver- 

 age of 152 eggs per individual in sticks containing 5 to 7 eggs. The 

 young larvae prefer to attack the fruit, of which an appreciable propor- 

 tion is destroyed in those areas where the insect is abundant. After 

 vacating the fruit or the originally attacked young cladode, each larva 

 enters a segment near the apex and tunnels downward. The entrance 

 hole is enlarged to a greater diameter than that of the developing larva 

 and is kept open by means of a silken lining. As the excrement is dis- 

 charged through this opening, the presence of larvae is rendered obvious 

 by the pellets of frass held in the webbing around the entrance hole. 

 This habit distinguished subumbrella from all other known forms of 

 Olycella. The larvae tunnel downwards from segment to segment 

 much more freely than those of 0. junctolineella; in the prickly pears 

 with smaller cladodes, the tunnel may extend through several cladodes 

 into the underground butt, or bulb. The cocoon resembles that of the 

 related species and is found among debris or just beneath the surface 

 of the soil. 



OLYCA Walker 



This genus is now limited to the West Indian insect Olyca phryganoides 

 Walker. 



