THE POLISTES ATERKIMA. 597 



sist of a mass of delicate threads that are not unlike those of the 

 common silkworm, which cross and recross each other so as to 

 fill up the hollow of the leaf, and to form a receptacle for the fu- 

 ture young. 



The insect is a large one, being a full inch in length, and of 

 rather a formidable appearance. In color it is black, with the 

 exception of a few narrow transverse streaks of bright yellow 

 upon the fore part of the thorax, and the abdomen is placed at 

 the end of a long foot-stalk. 



In connection with this branch of the subject, I must call the 

 attention of the reader to the curious cell group of Polisles aterri- 

 ma, a figure of which is given on page 482. 



At first sight it looks as if the winged architect had intended 

 to make a cell group like that of the Icaria, and had been brought 

 abruptly to a conclusion. A close inspection, however, shows 

 that the structure is intentional, and not merely the result of ac- 

 cident. The cells are all placed with their mouths downward, 

 and are set in a very peculiar manner. 



In the Icaria nests the cells are arranged so as to form a more 

 or less elongated mass, widest in the middle and tapering to the 

 end, the variation in width being caused by the different ar- 

 rangement of the cells, which are two deep at the commence- 

 ment, reach three or four deep at the middle, and are reduced 

 at the end to a single row of cells. But in the nest of the Po- 

 listes all the cells are two deep, being arranged in two regular 

 rows. 



On reference to the illustration, which is exactly one half the 

 length of the original specimen, the reader will see that the cells 

 are of different sizes, and might therefore fancy that the upper or 

 larger cells are those which nurture the larvas that are destined 

 to be perfect males and females, and that the lower or smaller 

 cells are intended for the workers or neuters. But a careful ex- 

 amination shows that such a supposition would not be correct. 

 It is true that the upper cells are larger than the lower, but this 

 increase of size is simply owing to the fact that they are com- 

 pleted, while the five lower cells are still unfinished. 



The attention of the reader is particularly called to the dark 

 bars which are at regular intervals across the cells. These are 

 not merely intended to represent effects of light and shade, nor to 

 show that the little architect has used materials of different colors 



