Page:Popular Science Monthly Volume 44.djvu/619

 animals, whose dwelling participates in the nature of a hollow cavern, make additions to it which claim a place among the constructions with which we are now occupied.

The Anthiophora parietina is in this group: it is a small bee which lives in liberty in our climate. As its name indicates, it prefers to frequent the walls of old buildings, and finds a refuge in the interstices, hollowing out the mortar half disintegrated by time. The entrance to the dwelling is protected by a tube curved toward the bottom, and making an external prominence. (Fig. 7.) The owner comes and goes by this passage, and as it is curved towards the earth the interior is protected against a flow of rain, while at the same time the entry is rendered more difficult for Melectes and Anthrax. These insects, in fact, watch the departure of the Anthophora to endeavor to penetrate into their nests and lay their eggs there. The gallery of entry and exit has been built with grains of sand, the débris produced by the insect in working. These grains of sand glued together form, on drying, a very resistant wall.

The other animals of which I have to speak are genuine masons, who prepare their mortar by tempering moistened earth.



Every one has seen the swallow in spring working at its nest in the corner of a window. It usually establishes its dwelling in an angle, so that the three existing walls can be utilized, and to have an inclosed space there is need only to add the face. It usually gives to this the form of a quarter of a sphere, and begins it by