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Show 42 ON THE TREE TRAPDOOR SPIDER. [Jan. 18, much time in smoking under one of these trees, saw an open trap, and drew my attention to it, and then they could be secreted no longer, for I searched every likely tree and made them my special care and study for some time. I have in m y possession two or three houses in which the doors have undergone modifications to meet the size of the spiders now residing in them. A small individual will sometimes take possession of the empty house of an adult; the new comer finds the door too large, so constructs another in such a way as to form a smaller opening; thus some houses have two doors : I send you a specimen. On attempting to lift the doors of these houses, the spiders hold them down with great firmness. Knowing that naturalists are uncertain as to the means used by the ordinary Trapdoor Spiders for holding down the traps, I have taken special care to observe the mode adopted by those which inhabit the trees, and I find that the hooks of the mandibles, which are barbed, grasp the door, and the legs the side of the house. I am quite sure that this is the case, for I have observed carefully, and in one instance, when the spider held on tenaciously, I was enabled to fix open the door and observe with a lens, and then to lift out the " fangs," which were buried deep in the silken door. I have often found the doors fastened down and not held. They are fastened by strong weavings of silk, which must be broken before the door can be lifted ; in all such cases the spiders do not appear to be active or to assist in keeping down the trap. Perhaps at such times the spider is engaged iu changing its skin, and, in cold weather, hybernating. Being anxious to see the spider capture its prey, I put a few grains of sugar near one of the doors. Two flies lighted on the sugar, and while they were regaling, the trap was thrown open with a slight click, the spider darted out, caught one of the flies and retired ; the whole transaction was done with such rapidity and dexterity that the other fly, though nearly touching the captured one, was undisturbed and seemed to be quite unconscious of the fate of its companion. I have observed one other capture, and this also was carried out with the same extreme rapidity. The spiders are probably nocturnal in their habits, though I have never seen them out at night, but I know that the work of building goes on during the night. The captures I observed were during the day. It may be that they work at night to save themselves from detection from some of their enemies, and watch for prey both day and night. The eggs are placed in a small silken bag at the bottom of the nest. When the eggs are hatched, the young live for several months a free life in the home of the parent, and are thus protected from the ants which infest the trees, until they are strong enough to build for themselves ; this they do while they are yet very small, but not until they are several months old. The greatest enemies these spiders have are the ants; but the houses are so strong and so much like the natural bark that even the ants would not work them much damage if they did not catch them, or enter the house accidentally. On old trees I have found nearly all the houses without spiders, but |