82 HYMENOPTERA 



the abundant genus Folistcs ; these Insects make hexagonal cells, 

 of paper -like material, forming an irregular comb, or mass, 

 attached to bushes by a stalk near its centre ; these nests are 

 placed so that the mouths of the open cells look downwards. 

 The species of Isclmogastcr (Fig. ;)-4) make layers of comb, con- 

 nected by a pedicel, but without any envelope ; these Insects 

 form a section of Stelocyttares called Gymnodomes. 



Most of the nests of the Poecilocyttares have only a single 

 layer of comb. The wasps of the genera Synoeca and Polyhid. 

 have the habit of spreading a layer of cells on a leaf, or on tlie 

 bark of a, tree, and of covering this with an envelope that is 

 pierced ])y a single orifice only, but that does not rest on tlie 

 cells, find so allows circulation of the Insects between the cells 

 and the envelope. This appears to be the arrangement in a 

 nest of Synoeca cyanca preserved in the British Museum ; in 

 this construction a large layer of cells is moulded on tlie Ijranch 

 of a tree, whose contour, for a length of two or three feet, it con- 

 sequently follows ; while outside the mass there is placed a con- 

 tinuous envelope, leaving a considerable distance between it and 

 the cells. 



It would lie impossible in the space at our disposal to give a 

 satisfactory account of all the forms of wasp-nests, and we must 

 therefore refer the student to de Saussure's work, confining 

 ourselves to a brief notice of some specially interesting forms. 

 The habitation of the Brazilian Polyhia {Myrcq^ctra) scutellaris 

 is a very solid, closed structure, covered externally with rough 

 knobs or angular projections. Although of very large size — 

 it may be u})wards of two feet in length — it is suspended from a 

 branch, and has but one orifice ; the arrangement of tlie combs 

 in the interior is that of the Phragmocyttares, they being 

 firmly attached to the outer envelope, and so placed as to form a 

 curved surface, the convexity of which is downwards : the number 

 of wasps in a well-developed nest of this kind must be very great. 

 This species is said to be a honey-gathering wasp. 



One of the best known of the South American wasps' nests is the 

 construction (Fig. 33) of Charteryiis chartarius ; these nests are so 

 regularly shaped, and formed of papier-mache so compact and solid, 

 as to look like stone : this edifice is attached in a very firm manner 

 to the branch of a tree, and has a single portal of entry beneath ; 

 its interior arrangement is nnich like that of Myrapctra scutellaris. 



