The Mason-Wasps 



gether from questions of temperature, why 

 the Pelopaeus has a preference for human 

 habitations, which afford the best protection 

 against damp. Under the mantels of our 

 chimneys she finds at one and the same time 

 the heat required by the larvae and the 

 necessary dryness for the nests. 



Before receiving its final coating, which 

 conceals the structural details, the 

 Pelopaeus' edifice does not lack elegance. 

 It consists of a cluster of cells, sometimes 

 arranged side by side in one row — which 

 gives the fabric something of the look of a 

 mouth-organ with reeds all short and all 

 alike in size — but more often grouped in 

 a varying number of layers placed one 

 above the other. In the most populous 

 nests I count as many as fifteen cells; others 

 contain only about ten; others again are re- 

 duced to three or four, or even to one alone. 

 The first appear to me to represent a mo- 

 ther's whole output of eggs; the second sig- 

 nify incomplete layings, deposited here and 

 there, perhaps because better sites were 

 found elsewhere. 



The cells are not far removed from the 

 cylindrical shape, with a diameter increas- 

 ing slightly from the mouth to the base. 

 80 



