68 OHIO BIOLOGICAL vSURVEY 



cactus of the plains, Opioitia niissouriivisis. (See also below under TW- 

 Hcella fasciata . ) 



Vloucella — The larvae of this genus show two distinct and interest- 

 ing habits. Some of them live in the nests of the large Aculeate Hym- 

 enoptera, others in cacti. The larvae of W inanis have been taken in the 

 nests of \'espa crabro (Sharp); V. bombylans from the nests oi Bombus 

 lapidarius and \^espa germanica. Verrall p. 486. 



"These larvae are pallid, broad and fleshy, surrounded by numerous 

 angular, somewhat spinose outgrowths of the body; and have behind a 

 pair of compound stigmata in the neighborhood of which the outgrowths 

 are somewhat larger." Sharp, Camb. Nat. Hist., Vol. VI, Part II, p. 

 500. (For a further discussion of this interesting habit see pp. 37, 40.) 



Hubbard in Psyche, May, 1899, suppl. I, i, gives the following note 

 on the occurrence of larvae of Vohnr/la avida in giant cactus, Ccreus 

 giganteus, in Arizona. "A grizzled old trunk had been chopped by 

 somebody's axe and had on one side a cavity about as large as my hat, 

 partly filled with black rotten material. The rotting was constantly 

 advanced by great numbers of huge dipterous maggots ( V. avida), etc." 



]\ fasciata: Larvae were found in the tissues of the common cactus 

 of the plains, Opuntia missoiinensis in Colorado. "Puparia from the 

 joints of O. missoiiriensis disclosed two allied Syrphids, Copestylum mar- 

 ginatum, Vohicella fasciata. The puparia were lodged deeply in cavities 

 within the stem, evidently the feeding place of the larva. The puparia 

 of the two species are scarcely distinguishable, both having a short, con- 

 joined stigmatic tube and two slender anterior projections." Ent. News, 



II, 162. 



Smith, Canad. Hnto. XXIII, 242 gives these notes on V. fasciata. 

 A lot of prickly pear cactus was examined and Lepidopterous larvae 

 removed from it. "A few days after a Dipterous pupa was noticed in the 

 jar which had been left undisturbed and eventually some 8 or 10 Syrphid 

 flies made their appearance. They could not have been parasites for all 

 the Lepidopterous larvae were accounted for, and I can only suppose 

 that either eggs or very small larvae were in the partly decaying flesh of 

 the infested leaves and these were overlooked because not expected." 



Buckton, "Nat. Hist, of Eristalis tcna.v," p. 84 gives the following 

 on V. pellucens: "The grubs are footless, but show small false feet with 

 minute hooks. The long spiracles at the tail end are absent. The larvae 

 are blind. The puparium is very like that of Eristalis and it develops 

 outward cornua. The case is provided with a hinged operculum which 

 remains attached after the fly has escaped." 



