THE SOLITARY WASPS. 267 



edge of a book between the projecting margins of the 

 boards. 



Amongst the species which exert a greater amount 

 of industry in the formation of their nests^ by digging 

 a hole for the reception of their progeny, instead of 

 adopting any cavity that they may chance to meet 

 with, none is more deserving of notice than the Ody- 

 nerus murarius, the Mason Wasp of Reaumur. It is 

 in the hardest sand that this insect constructs its 

 little tunnel, to a depth of two or three inches, and 

 the work is entirely performed with its mandibles, 

 assisted by a peculiar fluid which the little mason is 

 able to emit from its mouth. This doubtless serves 

 two purposes, for the materials removed are not 

 scratched out with the legs, as is the case among the 

 Fossoria, but the detached particles of sand are worked 

 up into little pellets, which are then carefully carried 

 to the entrance and applied to the construction of a 

 tubular tunnel, which rises from the mouth of the 

 nest at first in a straight line, but with a considerable 

 curve towards the top. The object of this arrange- 

 ment is probably twofold : during the formation and 

 storing of the nest, the long cylindrical tunnel may 

 undoubtedly serve as an outwork to the citadel, and 

 deter the parasitic insects which are constantly on 

 the look-out for a receptacle for their eggs, from ven- 

 turing into the interior ; and when the nest is com- 

 pleted and the eggs laid, the pellets of which the tube 

 is composed furnish a convenient supply of materials 

 for filling up its mouth, and are employed for this 

 purpose. 



With incredible labour and perseverance the mother 

 Wasp forms several of these cells, in each of which 

 she deposits a single egg, accompanied by a supply of 



n2 



