DEVELOPMENT OF A PARASITE. 497 



The insect which is here shown is called Trigonalys comprcssi/s, 

 and is a native of tropical America. The following account of 

 its mode of development is given by Mr. F. Sndth : — 



"John Macgillivray, Esq., Naturalist to her Majesty's ship 

 Rattlesnake, lately presented to the British Museum the nest of 

 a South American species of Polistes, which he says is very 

 abundant at St. Salvador, where even in the street it attaches 

 its nest under the eaves of houses ; this species is the Polistes 

 lanio of Fabricius, and in all probability the Vespa Canadensis 

 of Linnaeus ; a specimen of the species is preserved in the 

 Banksian Cabinet. 



" On examining the nest, I found it consisted as usual of a 

 single comb of cells, having in the centre, at the back, a small 

 footstalk, by which the nests are attached in their position ; tlie 



■/; -^^^ 



Fn;. ■JiJS. — Trigonalys coiiifiri'ssus. 

 (Black ) 



comb contained sixty-tive cells, the outer ones being in an un- 

 finished state, whilst twenty-two of the central ones had remains 

 of exuviffi in them, and one or two closed ones contained perfect 

 insects in them ready to emerge. About half a dozen of the 

 wasps had the anterior portion of their bodies buried in the 

 cells, in the manner in which these insects are said to repose. 



" In one cell I observed the head of an insect evidently of a 

 different species, it being black and shining. On extricating it 

 I discovered it to be a species of Trigonalys; I subsequently 

 carefully expanded the insect, and it proved to be the Trir/onali/s 



