82 HYMENOPTERA 



CHAP. 



the abundant genus Polistes ; 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 Ischnogastcr (Fig. 34) make layers of comb, con- 

 nected by a pedicel, bat 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 Polylia 

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

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

 pierced by a single orifice only, but that does not rest on the 

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

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

 nest of Synoeca cyanea preserved in the British Museum : in 

 this construction a large layer of cells is moulded on the branch 

 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 be 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 Polybia (Myrapetra) scuti-llni-i* 

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

 knobs or angular projections. Although of very large size- 

 it may be upwards of two feet in length it is suspended from a 

 branch, and has but one orifice ; the arrangement of the 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 Chartergus 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 much like that of Myrapetra scute/ />//!*. 



