NESTS OF APOIOA. 603 



as if made of sand-paper, or from the skin of a dogfish. One or 

 two, again, are much darker than the others ; while one is almost 

 white, with only a tinge of gray. 



Another point in these nests is, that although they vary so 

 much in diameter, their thickness is almost uniform. The reason 

 is evident enough. As the young larvae attain a tolerably uni- 

 form size, and are not boldly divided into large males, larger 

 queens, and little workers or neuters, the cells are of equal length. 

 Therefore, whether the number be great or small, the thickness 

 of the cell group remains unchanged, though the diameter may 

 increase to any reasonable amount;. 



All the nests are fixed in the same manner, a branch or twig 

 passing through the upper surface. When the nest increases in 

 size, the original support is often found to be too slight, and in 

 that case others are added. The smaller nests are upheld by a 

 single twig only, but the largest is supported at no less than three 

 points, two tolerably stout branches passing through the side of 

 the cover, and a smaller twig supporting the top. 



Another point to be noticed is, that the size of the nest is no 

 criterion of its shape. It is not necessarily circular because it is 

 large, nor horizontal because it is small. The eight examples in 

 the British Museum show every gradation of shape between the 

 hexagon and the circle, without the least reference to size. 



How the insect forms these wonderful cell groups is an enigma 

 to which not the least clew can be found. In proportion to the 

 size of the architect, they are simply enormous, and yet the sides 

 and angles are as true and just as if they were single cells. It is 

 very clear that neither the theory of excavation or of equal press- 

 ure can apply to these nests, and an additional reason is afforded 

 why these theories should be abandoned. It is to be regretted 

 that the only reasoning is of the destructive kind ; but at present 

 we have no data on which to found a theory that seems in the 

 least tenable. 



In the nest to which reference has been made, the insects have 

 carried out the hexagonal principle in a curious manner. A 

 number of cells whose mouths are closed with a white silken cov- 

 er prove that the inmates are undergoing their metamorphosis, 

 and are in a transitional state between the larva and the perfect 

 insect. Instead, however, of being scattered at random through- 

 out the nest, the inhabited cells are arranged in the most system- 

 atic manner, a group occupying the centre, and being surrounded 



