LIST OF PRINCIPAL CACTUS INSECTS. 



39 



plied. The very leathery integument seems to protect the insect 

 against desiccation, and in other ways the larva has evidently adapted 

 itself to long periods of waiting for favorable food, which, in the arid 

 regions, depends upon the infrequent rains. 



Stictomyia longicornis Bigot. 1 



The Stictomyia longicorrds of Bigot is an exceedingly common 

 insect throughout the cactus area. The adults are small flies with 

 spotted wings. The wings are bent downward at about the middle. 

 so that the name of " droop-winged fly " seems appropriate. (See 

 fig. 8.) The larvae occur along with Copestylum, Volucella, and 

 Hermetia in o.ny part of the cactus plant that may be injured. They 

 also infest wounds made by knives when cuttings are removed for 

 planting. 



The remaining insects 

 lifted as scavengers are of 

 less general occurrence than 

 the species mentioned in 

 the preceding pages and 

 no special notes have been 

 made upon them. 



LIST OF THE PRINCIPAL 

 CACTUS INSECTS OF THE 

 UNITED STATES. 



Fig. 8. — A cactus insect, Stictomyia longicornis: a 

 Adult in profile ; &., head ; c, wing. Enlarged. 

 (Original. > 



The following list deals 

 primarily with the species 

 attacking or associated 

 with the genus Opuntia and includes all published records of 

 previous investigators. Many forms not restricted to Opuntia are 

 included because, as Mr. Schwarz has pointed out, the insects of that 

 plant are interchangeable with those of other plants of the family 

 Cactacea\ For this reason we have included all of the records of 

 species taken on Cereus giganteus in Arizona by Mr. H. G. Hubbard. 2 

 The names of such species are preceded b}^ an asterisk. We have also 

 included references to some exotic species, principally from Mexico. 



The published records of cactus insects, including those of Mr. 

 Hubbard, deal with 105 species. The present list includes 324 spe- 

 cies. These are divided, for convenience, into the following groups: 

 Injurious 92, parasitic or predaceous 28, scavengers 73, visitors of 

 flowers 40. incidental 91. 



1 Order Diptera, Family Ortalidae. 



2 Except Platydemu inquUinum Linell. which was taken in a rat's nest. 



