CACTUS-FEEDING INSECTS AND MITES 67 



plants of the prickly pear the greater proportion of the fruit may be 

 destroyed by the larvae. 



A special investigation of the life history and habits was conducted 

 in 1925 at Uvalde, Texas, both in the field and under cage rearing 

 conditions. Since young larvae were prevalent in early May, adults 

 of the overwintering generation had evidently emerged in April, 

 during or immediately following the main flowering period of Opuntia 

 lindheimeri. These larvae entered and fed within the dying flower 

 head, being often found in the style, and then attacked the developing 

 fruit. They rarely penetrated from the flower dirough the crown. 

 The usual practice was to move from the flower and to enter an ad- 

 jacent fruit near the base, preferably where two fruit were in contact. A 

 semicircular web of silk, mixed with frass, spun around the entrance 

 hole served both for protection and for attaching the fruit to an adja- 

 cent one or to the segment. The larvae tunnelled in the fleshy portions 

 of the fruit, which rotted or dried up. It was rare to find more than 

 one larva in a fruit. The life cycle was completed in 5 to 6 weeks, the 

 adults emerging from May 21 to the middle of June. 



A portion of the second generation attacked the relatively small 

 second crop of flowers and young fruit produced by some plants of 

 0. lindheimeri, and the flower heads and young fruit of the late bloom- 

 ing 0. cacanapa. The behavior of the larvae corresponded with that 

 of the first generation; the life cycle occupied 4 to 5 weeks, and the 

 moths emerged at the end of June and in July. The major part of this 

 generation, however, infested the well-developed green fruit. The 

 newly hatched larvae entered the fruit near the crown and penetrated 

 directly to the seed cavity, where they fed on the fleshy covering of 

 the seeds for 4 to 5 weeks or even longer. Development was gradual, 

 and the feeding set up no decay; hence, the presence of the small 

 larva could not be detected by outside indications. When the fruit 

 turned red or purple preparatory to ripening, the larva tunnelled 

 through the fleshy portions; a discharge hole was formed, often near 

 the base of the fruit, and was covered with a small amount of webbing 

 serving to attach the fruit. After leaving the seed cavity, larval growth 

 was accelerated. It seemed that successful development was contingent 

 on the ripening of the fmit. The existence of a small larva in the seed 

 cavity tended to cause early ripening; the few colored fruit among 

 a green crop almost invariably contained Ozamia larvae. The fruit be- 

 came easily detached and often fell to the ground or were suspended 

 by the larval webbing. The life cycle occupied 8 to 9 weeks, almost 

 twice as long as that of the smaller portion of the generation infesting 

 the late flowers. Moth emergence occurred from July 22 to August 10. 



