50 U.S. NATIONAL MUSEUM BULLETIN 256 



The species is not uncommon, at times becoming abundant. In 

 August 1936 larvae were very numerous in northern Tucuman; in 

 many local areas almost every plant of 0. sulphurea was attacked, 

 while a field of . ficus-indica supported a heavy population. A survey 

 of the Province of La Rioja established its prevalence both in the 

 open semidesert country and in the mountains at altitudes up to 

 7,000 feet. 



The normal food plant is Opuntia sulphurea, which, although a low- 

 growing plant, possesses larger, thick cladodes. In northern Tucuman, 

 the tree pear 0. ficus-indica is frequently attacked, while the larger tree 

 pear 0. quimilo is occasionally infested. In the Province of Mendoza 

 larvae have been found in the small round-jointed 0. russellii, a member 

 of the subgenus Tephrocactus, but other members of this group, such as 

 0, aoracantha and 0. glomerata, which occur freely in the western Prov- 

 inces, have not been recorded as hosts. 



The narrow-jointed prickly pears 0. utkilio and 0. discolor are not 

 subject to attack, even though, in northern Tucuman, they grow in tlae 

 neighborhood of infested 0. sulphurea and 0, ficus-indica. Under cage 

 conditions in Argentina tlie female moths deposited eggs as freely on 

 0. aurantiaca (a close relation of 0. discolor), 0. utkilio, and the shrub 

 pear 0. bonaerensis, as on 0. sulphurea. Furthermore, in the short summer 

 generation the species was carried through its life cycle on 0. aurantiaca 

 and 0. utkilio, and the percentage of larvae that developed from the 

 egg to the pupal stage on these two plants was not appreciably lower 

 than on 0. sulphurea; however, on 0. bonaerensis the larvae fed readily 

 but did not complete development. Similar rearing experiments on 

 two occasions with the long winter generation were not successful: 

 in the first year larvae survived for 180 days on 0. utkilio and 0. bonae- 

 rensis, attained full size, but did not pupate; in the second year a few 

 larvae on 0. utkilio and 0. aurantiaca reached the pupal stage, but no 

 moths were obtained. 



In Australia, under cage conditions, this insect was reared with 

 some degree of success on the shrub pears 0. inermis and 0. stricta and 

 on the tree pears 0. tomentosa and 0. streptacantha. Although attempts to 

 establish it in the field failed, it is known that a few colonies passed 

 through the life cycle on both 0. tomentosa and 0. inermis. 



C. doddi resembles C. cactorum, closely in appearance, life history, and 

 habits. The moths of doddi are of a general deeper brown tint than those 

 of cactorum, and the hindwings are uniformly dusky in the female. The 

 eggstick habit is well developed, although the average number of eggs, 

 60-65, tends to be lower; the maximum number of eggs in a stick has 

 been 90. The individual eggs are larger than those of cactorum, and 

 freshly deposited eggs are slate-colored instead of whitish. The larvae 



