320 WASP STUDIES AFIELD 



In all of the channels and nests may be seen, on the side- 

 walls, the mandible-marks, in lateral strokes, or half-rings, 

 where bites were taken out horizontally, not up and down. 

 (See fig. 63.) The figure also betrays the method of pro- 

 cedure in nest-digging: as the length of the burrow in- 

 ci eases, the width also increases, so that at the bottom there 

 is a start on the first globular cell. When this has been 

 completed and provisioned and the egg deposited, undoubt- 

 edly the widening of the second cell occurs, and perhaps 

 the soil removed in this widening goes to form the plug 

 for the lower cell. 



When the home is at last in order and Madam Odyncrus 

 goes a-marketing, she does precisely what most other wasps 

 scrupulously avoid : she leaves her nest wide open. To be 

 sure, there is yet nothing in it to attract or reward marau- 

 ders, but neither is there in the newly-finished burrows of 

 other species, so one is again left wondering what may have 

 been the origin of such an instinct what condition can 

 have brought such pressure upon the species as to estab- 

 lish in them so fixed a habit. 



Iseley (loc. cit. p. 289) was very fortunate to observe 

 her hunting in a patch of mallow. When 0. dor sails 

 comes upon a crumpled leaf containing the larva of the 

 spotted skipper, she commences tearing energetically at the 

 silken nest, first at one end and then at the other. Some- 

 times more than five minutes is required to dislodge a 

 caterpillar, but more often the victim is jerked from its 

 cover in less than a minute, seized by the neck and stung 

 two or three times under the thorax. Vigorous malaxation 

 follows the stinging, after which the caterpillar is carried 

 to the nest without delay. 



These wasps, when returning from the field, seem to 

 experience no difficulty whatever in locating their bur- 

 rows. They carry their prey on the wing, usually with com- 



