124 



HYMENOPTERA. 



"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. 



"5. When a fourth side exists in the basal pj-ramid, it may 

 •be in consequence of irregularit}- 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 

 A E c will be seen by refer- 



ence to Figs. 73 and 

 74 ; the first repre- 

 Fig. 73. 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 a B c 



series 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 

 JB, 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, 

 A . C and two equal hexagons. B, Fig. 



Fis 



74, represents the sides of the same 

 cell, which, instead of forming three 

 trapeziums, as at A, a, h, 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 sjmmetrical in itself. No pre- 

 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. 



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



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



iiiiii I 



Fis:. 75. 



