514 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1910. 



already mentioned. The materials are noticeably economized, which 

 indicates a constructive ability more certain and more refined. The 

 coating of earth is diversified externally by a multitude of transverse, 

 parallel corrugations, which correspond to the bands of successive 

 accretions during construction. At a distance the whole structure 

 presents the appearance of a small rude basket. 



The construction of the cell is begun at the bottom. The wasp 

 molds its work, building up the earth in regular fashion around the 

 whole breadth of the cell. It deposits its material on one side in 

 contact with the substratum. Then, moving backward, it distributes 

 the Avhole evenly as regards thickness, according to the predetermined 

 diameter of the structure. It carries on this work with extreme care 

 and zeal, inten^upting its toil as mason and architect only to go 

 hastily to gather new materials, which, as a rule, it gathers in a sin- 

 gle spot. Two or three days are necessary for the Synagris to com- 

 plete its basket of earth. Then the work is suspended for a time. 

 The wasp lays an Qgg in the cell, and the new occupations of mother 

 and nurse follow that of worker in clay. "Wlien the larv^a, which is 

 born and develops in the cell, has completed its growth, the insect 

 closes' the orifice of the cell with a cover of earth, the material for 

 which it frequently takes from the walls of the entrance passage, or 

 neck, so that the opening is often transferred to the end of the main 

 axis of the cell. 



The task being finished, the insect returns to its labors of construc- 

 tion, goes to look for suitable materials, and builds a new cell at the 

 side of the preceding one, and in the same form. The maximum 

 number of different cells which may compose the aggregate of an old 

 nest appears not to exceed six, on the average, for a single female. 

 Every time that a new cell is built, it is attached firmly to the pre- 

 ceding ones, and a mass of earth filling the interstices conceals in 

 part the original distinctness of each cell, and also frequently covers 

 the bands of the fundamental coating. The uniting of the different 

 cells, however, is never so complete and never produces so compact a 

 mass as in the case of the nests of the preceding species of Synagris. 

 The appearance of the nest is quite different. 



The arrangement of the cells in an old nest, and consequently the 

 general form of construction, varies according to the orientation of 

 the whole. Most commonly the successive cells are placed in juxta- 

 position in a linear series, in a single row along the substratum. The 

 complete nest formed by this manner of assembling takes the shape of 

 a band of earth more or less regular and compact, about 6.50 centi- 

 meters in breadth for a nest of four cells, and 3.50 centimeters in 

 height (pi. 3, fig. 3). The different cells are often recogTiizable only 

 by the orifices, which are all arranged on the same side, whether open 

 or closed. The nests with the cells in a single row are the most 



