Instinct and Discernment 



The Mason-bee of the Pebbles (Chali- 

 codoma parietina) has none of this elas- 

 ticity in the choice of a site. In her case, 

 the smooth stone of the parched uplands is 

 the almost invariable foundation of her 

 structures. Elsewhere, under a less clement 

 sky, she prefers the support of a wall, which 

 protects the nest against the prolonged 

 snows. Lastly, the Mason-bee of the 

 Shrubs (C. rufescens, PEREZ) fixes her ball 

 of clay to a twig of any ligneous plant, 

 from the thyme, the rock-rose and the 

 heath to the oak, the elm and the pine. 

 The list of the sites that suit her would 

 almost form a complete catalogue of the 

 ligneous flora. 



The variety of places where the insect 

 installs itself, so eloquent of the part played 

 by discernment in their selection, becomes 

 still more remarkable when accompanied 

 by a corresponding variety in the architec- 

 ture of the cells. This is more particu- 

 larly the case with the Three-horned Os- 

 mia, 1 who, as she uses clayey materials very 

 easily affected by the rain, requires, like 

 the Pelopaeus, a dry shelter for her cells, a 

 shelter which she finds ready-made and uses 



1 Cf. Bramble-bees and Others: passim. Translator's 

 Note. 



167 



