SOLITARY WASPS OF GENUS SYNAGRIS EOUBAUD. 515 



regTilar and perfect. In their construction the powers of /S. cornuta 

 in comparison with those of other species are most fully revealed. In 

 other instances the cells are placed one upon another in several rows, 

 the orifices being sometimes in the same direction and sometimes dis- 

 tributed at random. The mass which fills the intervals between the 

 cells may produce a compact and amorphous nest. 



The dimensions of these compact nests, which are always less than 

 those of other species of Synagris for the same number of cells, the 

 greater thinness of the walls, and the difference in the ornamentation 

 of the outer coating, enable them to be readily distinguished. 



Orientation of the nests. — The orientation of the orifice of the cell 

 is variable, as well as that of the whole nest. The wasp knows how 

 to modify slightly, according to circumstances, the general direction 

 which is suitable for the cells. It adapts its constructions to the dif- 

 ferent conditions existing where the nests are placed. The linear nests 

 are ordinarily placed horizontall}^ if the breadth of the foundation 

 permits and the openings of the cells occupy the highest point. In 

 other cases, especially when a nest is placed on a strongly inclined sur- 

 face, such as the underside of a roof, the orifices are turned a little 

 more outward. The length of the entrance passage, or neck, and the 

 position of the orifices vary according to the inclination of the foun- 

 dation. A'Vlien a nest is fixed to the lower surface of a horizontal wall 

 the entrance to the cells looks downward (pi. 3, fig. 2) in accordance 

 with the development of the neck. Sometimes, though rarely, the wasp 

 nests in the bushes away from habitations. It may then use as sup- 

 ports for its cells the broad and firm leaves of certain herbaceous 

 l^lants, but it takes care to conceal the nest on the underside of the 

 leaves which, being bent downward by the weight, form a roof for it. 

 A\nien the nest is attached to a narrow leaf, the breadth of which 

 scarcely exceeds the maximum dimensions of a single cell, the orienta- 

 tion of tlie nest is entirely changed. The cells are placed according 

 to the breadth of the leaf and piled one on another. A linear nest 

 results, but is oriented in accordance with the lenglh of the blade, 

 the orifices of the cells being placed laterally. These facts show a 

 certain elasticity in the manifestations of the constructive powers of 

 Synagris cornvta.^ which we did not find in our other two species. 



Ovulation and rearing of the larva. — ^Wlien the Synagris has fim- 

 ished the construction of its cell of earth, it lays a bluish egg., measur- 

 ing G millimeters long, the chorion of which presents at one of the ex- 

 tremities the rudiment of a terminal filament. This is the rudiment 

 of the suspensory thread of the egg. which among a large number 

 of eumenids secures the egg to the wall of the cell. After the egg is 

 laid, the female remains in the nest, her head being turned toward 

 tlie orifice. She is observed to be absent only for brief periods at 

 long intervals, no doubt leaving in search of food. She does not. 



