THE TATUA MOPIO. 153 



The tiers of cells are variable in number ; a rather remarkable 

 fact, as the floors are made before the cells are built. In a good 

 specimen of this nest in the British Museum there are only 

 four tiers of cells. How many tiers are completed before the 

 insects begin to afiix cells to them, or whether the cells are made 

 as soon as the floors are finished, are two points in the history 

 of this wasp which have not yet been decided. These floors 

 extend completely to the walls, to which they are fastened on 

 all sides, and the insects gain admission to the different floors 

 by means of a central opening which runs through them all. 



In Mr. Waterton's museum, at Walton Hall, are several speci- 

 mens of these nests, one of which is opened so as to show the 

 interior, as well as the central aperture, the whole of the bottom 

 being cut away and raised like the lid of a box. The substance 

 of this nest resembles thin brownish pasteboard, and, as is the 

 custom with most of the wasp tribe, the cells are placed with 

 their mouths downward, the nurses being enabled to attend to 

 their charges by remaining on the floor of the next tier of cells. 

 Taking one row of cells as an average, I counted twenty-four 

 from the central aperture to the circumference, thus giving a 

 tolerable notion of the number of cells in each tier. The aper- 

 ture is not precisely in the middle, so that some rows of cells 

 are necessarily larger than others, but I purposely selected a row 

 which seemed to afford a fair average. 



There are also certain British wasps which always make 

 pensile nests, though none of them are so complicated or so 

 finely constructed as those of the pasteboard wasps of hotter 

 climates. 



These are popularly called Tree Wasps, and the best known 

 among these pensile wasps is the insect which is sometimes 

 known as Vespa Britafmica, but which is now named Vespa 

 Norwegica, and may therefore be called the Norwegian 

 Wasp. 



Of the species in question Mr. Smith remarks that it is rare 

 in the South and West of England, but is not uncommon in 

 V^orkshire and plentiful in Scotland. It seems to be a nocturnal 

 insect, for a collector of lepidoptera found that when 'sugaring' 



