v SOCIAL HOMES 187 



posed of only one layer of material, at times very 

 thick and resisting, at others slight and supple. Of 

 this substance, after the manner of Vespa, the wasps 

 usually build a papyraceous envelope or sac for the 

 inclosure of their combs, and as in that genus,* the 

 covering follows closely the direction of the plan of 

 the cells. These nests attain an extraordinary degree 

 of development and house a vast multitude of in- 

 dividuals; even our nests of Vespa, the best suited of 

 the previous category to support large populations, 

 are extremely limited compared with some of the 

 societies in question. The cause of the excessive in- 

 crease is unknown, whether it be that these societies 

 are formed on other bases, or that the climates that 

 give them birth do not impose such stringent peri- 

 odic destruction upon them as our winter season 

 does upon those at home. Exposure to the more 

 favourable climatic conditions, however, does not lead 

 to great increment among Vespa and Polistes ; many 

 of these companies abroad can hardly be said to be 

 less scanty than ours, and it seems not unreasonable 

 to conclude that a distinct difference lies at the root 

 of the economy of the two classes. 



The genus Chartergus, one of the important 

 groups of the cardboard makers, includes insects 

 apparently similar which practise two strangely 

 different forms of nidification. The nests of C. 

 chartarius, the most common in collections, are of 

 frequent occurrence in tropical America. Their card- 

 board is white, gray, or of a buff colour, tending to 

 yellow, very fine and of polished smoothness ; at the 

 same time it is strong and so solid as to be imper- 



