The _Anthophora 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 towards the bottom, and making an external prominence. (Fig. 35.) 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 endeavour to penetrate into their nests and lay their eggs there. The gallery of entry and exit has been built with grains of sand, the _debris_ produced by the insect in working. These grains of sand glued together form, on drying, a very resistant wall.[101] [101] Latreille, "Observations sur l'abeille parietine (_Anthophora parietina_)," _Annales du Museum d'Hist. Nat._, t. iii., 1804, p. 257. 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 utilised, and to have an enclosed 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 applying earth more or less mixed with chopped hay against the walls which are to support the edifice. At the summit of the construction a hole is left for entry and exit. During the whole of its sojourn in our country the Swallow uses this dwelling, and even returns to it for many years in succession, as long as its work will support the attacks of time. The faithful return of these birds to their old nest has been many times proved by attaching ribbons to their claws; they have always returned with the distinctive mark. [Illustration: FIG. 36.]