30 



PRINCIPAL CACTUS INSECTS OF UNITED STATES. 



This species is distributed throughout the cactus region. It has 

 been taken as far north as Denver, Colo., and as far south as San 

 Diego, Tex. Its range extends into Arizona. 



The winter is passed in the pupal state within the cells in the 

 Opuntia joints. The adults issue from April to June. There ap- 

 pears to be only one brood during the season. The species is re- 

 sponsible for a large amount of disfiguration of the cactus joints, but 

 as the cells are largely superficial the growth of the plant is not 

 seriously affected. In fact, in no cases observed have the joints been 

 found to be destroyed primarily by the insects. In some cases, how- 

 ever, the cells attract scavengers of various species, which increase 

 the diseased area and may cause the destruction of the joints. The 

 adults appear to feed by scraping the epidermis from the sides of the 



joint. 



Gerstseckeria nobilis Le 

 Conte. 



The work of Gers- 

 tceckeria nobilis Le 

 Conte (fig. 3) is pre- 

 cisely like that of the 

 preceding species ex- 

 cept that the cells con- 

 taining the immature 

 stages are located on 

 the margins of the 

 joints. In these locali- 

 ties a hard black ex- 

 udation frequently forms, and this interferes with the development 

 of new growth. For this reason it is more important than the pre- 

 ceding species, although it is of less extensive distribution. Our 

 records include many localities in Texas from Dallas to Corpus 

 Christi. It does not appear, however, to extend far to the west, 

 Hondo being the westernmost locality in our records. 



Gerstaeckeria clathrata Le Conte. 



Gerstwckeria clathrata Le Conte works exclusively on Opuntia 

 leptocaulis, so far as known, although it may rarely infest allied 

 species. Its work in the plants is similar to that of the other species. 

 It is partial to the new growth, which is often killed. Although 

 thus more destructive than the preceding forms, it is of less economic 

 importance on account of the uselessness of its host. It is recorded 

 from Colorado to Brownsville, Tex., and westward to Arizona. 



A fourth species, G. hubbardi Le Conte, was reared from Opuntia 

 vulgaris in Florida by Mr. H. G. Hubbard. It appeared to follow 

 the work of Melitara prodenialis Walker. 



Fig. 



-A cactus weevil, Gerstmckcria nobilis: Adult. 

 Enlarged. (Original.) 



