38 



PRINCIPAL CACTUS INSECTS OF UNITED STATES. 



In the -nine category as the preceding species are four species of the 

 closely allied genus Vblucella, namely, eswnens, avida, pvsilla^ and 

 fasciaia. They have been found numerously in practically all locali- 

 ties where cactus insects have been collected, occurring frequently 



with ('<>[>< sti/lum marginatum Say and other species. 



Hermetia spp. 1 



brown, its surface densely 



Almost equally important are two species of Hermetia. namely. 

 chrysopila (fig. 7) and hunteri. The former is much more abundant 



and occur-, from Dallas, Tex., southward to San Antonio and west- 

 ward as far as Los Angeles, Cal. 



The larva' of Hermetia chrysopUa Loew measure 35 mm. by 10 mm.. 

 the i ail 2 mm. The integument is very tough and leathery, dark 



and evenly punctured, with indistinct 

 transverse rows of callosi- 

 ties near the posterior 

 third. The head is deeply, 

 longitudinally impressed 

 below, with two longitudi- 

 nal ridges above. 



This species has beeu 

 collected from April until 

 September and has been 

 observed depositing eggs 

 in the empty cells of Ger- 

 stseckeria as well a- in the 

 opening- made by Mel it a ra 

 and other species. It is 

 not at all restricted to 

 cactus, but undoubtedly 

 breeds in decaying vegetable matter of any description. The adults 

 are found in flowers of many species as well as in those of Opuntia. 

 The most remarkable observation made on this species relate- to 

 the longevity of the larva. In May, 1909, a number of specimens 

 which appeared to be nearly full grown were taken at Hondo. Tex.. 

 by Mr. J. D. Mitchell. They were placed in breeding cages, from 

 which adult- appeared irregularly between July 17 and Augu-t 19. 

 Soi :c «»)' the Larvae, however, did not yield adults. They remained 

 motionless in the bottom of the cages. Whenever a new supply of 

 lood iu the form of decaying cactus was introduced they began feed- 

 ing, hut as soon as the food dried they became quiescent After it 

 was observed that they were of rather remarkable longevity no food 

 was introduced [\>v over a year. The larvae lived for more than 15 

 months without food and developed readily later when food was sup- 



FlG. 7. — A cactus insect, Hermetia chrysopila 

 Enlarged. (Original.) 



Adult. 



Order Diptera, Family Stratiomyiidse. 



