124 



HYMENOPTERA. 



B 



4. The relative size of the rhombic faces of the pyramidal 

 base is liable to frequent variation, and this where the cells are 

 not transitional from one kind to another. 



' k 5. When a fourth side exists in the basal pyramid, it may 

 be in consequence of irregularity in the size of the cells, or of 

 incorrect alignment of them on the two sides of the comb." 



Sometimes one of the faces is lost, and a new one formed, 

 so that all the basal portion of the cell becomes reversed, as 

 ABC will be seen by refer- 

 ence to Figs. 73 and 

 74 ; the first repre- 

 7:J - senting the cells when 



the base is viewed, and the second when looked at perpendic- 

 ularly to one of the sides. In both figures A indicates the 

 ordinary form of the cell. The whole 

 scries of Fig. 74 shows the gradual 

 introduction of the new face, which 

 is seen on the lower border, and the 

 elimination of one of the original faces, 

 which is seen on the upper border. At 

 B, which is intermediate between the 

 two extremes, the four faces consist of two equal rhombs, 

 one of which is the outgoing and the other the incoming one, 



and two equal hexagons. B, Fig. 

 74, represents the sides of the same 

 cell, which, instead of forming three 

 trapeziums, as at A, , b, c, now 

 form two pentagons, a' and c', and a 

 parallelogram, b'. At C, Figs. 73 

 and 74, the forms are in all respects 

 the reverse of those of A. A and C 

 are symmetrical with each other, and 

 B is symmetrical in itself. No pre- 

 Fig. 75. cise number " of cells is necessary 



for the purpose of making this transition, for it may take 

 place in two or three, or extend through a long series, as in 

 Fig. 73. 



"0. Ordinarily, the error of alignment does not amount to 

 more than one or two diameters of a cell. But occasionally 



a v 

 Fig. 



c 



4. 



C " 



