88 SOCIAL LIFE IN THE INSECT WORLD 



Let us cut the nest in half transversely. We shall 

 then see that the mass of eggs constitutes an elongated 

 core, of very firm consistency, surrounded as to the 

 bottom and sides by a thick porous rind, like solidified 

 foam. Above the eggs are the curved plates, which are 

 set very closely and have little freedom ; their edges 

 constituting the zone of issue, where they form a double 

 series of small overlapping scales. 



The eggs are set in a yellowish medium of horny 

 appearance. They are arranged in layers, in lines 

 forming arcs of a circle, with the cephalic extremities 

 converging towards the zone of issue. This orientation 

 tells us of the method of delivery. The newly-born 

 larvae will slip into the interval between two adjacent 

 flaps or leaves, which form a prolongation of the core ; 

 they will then find a narrow passage, none too easy to 

 effect, but sufficient, having regard to the curious pro- 

 vision which we shall deal with directly ; they will then 

 reach the zone of issue. There, under the overlapping 

 scales, two passages of exit open for each layer of eggs. 

 Half the larvae will issue by the right-hand passage, half 

 by that on the left hand. This process is repeated for 

 each layer, from end to end of the nest. 



Let us sum up those structural details, which are 

 not easily grasped unless one has the nest before one. 

 Lying along the axis of the nest, and in shape like a 

 date-stone, is the mass of eggs, grouped in layers. A 

 protective rind, a kind of solidified foam, envelops this 

 core, except at the top, along the central line, where the 

 porous rind is replaced by thin overlapping leaves. The 

 free edges of these leaves form the exterior of the zone 

 of issue ; they overlap one another, forming two series of 



