DASVGASTRES — MASON-BEES 37 



This Insect has been the object of some of J. H. Fabre's 

 most instructive studies on instinct.^ Although it is impossible 

 for us here to consider in a thorough manner the various points 

 he has discussed, yet some of them are of such interest and im- 

 portance as to demand something more than a passing allusion. 



AVe-have mentioned that the nest of Chalicodoma is roofed 

 with a layer of solid cement in addition to the first covering 

 with which the bee seals up each cell. When the metamorphoses 

 of the imprisoned larva have been passed through, and the moment 

 for its emergence as a perfect Insect has arrived, the prisoner has 

 to make its way through the solid wall by which it is encom- 

 passed. Usually it finds no difficulty in accomplishing the task 

 of breaking through the roof, so that the powers of its mandibles 

 must be very great. Eeaumur has, however, recorded that a nest 

 of this mason-bee was placed under a glass funnel, the orifice of 

 which was covered with gauze, and that the Insects when they 

 emerged from the nest were unable to make their way through 

 the gauze, and consequently perished under the glass cover ; and 

 he -concluded that such insects are only able to accomplish the 

 tasks that naturally fall to their lot. By some fresh experiments 

 Fabre, however, has put the facts in a different light. He 

 remarks that when the Insects have, in the ordinary course of 

 emergence, perforated the walls of their dark prison, they find 

 themselves in the daylight, and at liberty to walk away ; when 

 they have made their escape from a nest placed under a glass 

 cover, they, having no knowledge of glass, find themselves in 

 daylight and imprisoned by the glass, which, to their inexperience, 

 does not appear to be an obstacle, and they therefore, he thought, 

 might perhaps exhaust themselves in vain efforts to pass through 

 this invisible obstacle. He therefore took some cocoons contain- 

 ing pupae from a nest, placed each one of them in a tube of reed, 

 and stopped the ends of the reeds with various substances, in 

 one case earth, in another pith, in a third brown paper ; the 

 reeds were then so arranged that the Insects in them were in a 

 natural position ; in due course all the Insects emerged, none of 

 them apparently having found the novel nature of the obstacle a 

 serious impediment. Some complete nests were then taken with 

 their inmates, and to the exterior of one of them a sheet of 

 opaque paper was closely fastened, while to another the same 



' Souvenirs entomoloyiqiies. 1 -vols. Paris, 1879 to 1891. 



