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Page:Popular Science Monthly Volume 38.djvu/204

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THE POPULAR SCIENCE MONTHLY.

not to be cheated out of its proposed domicile, Stothis proceeded to erect a cylindrical case about two inches long, composed of a conglomerate gathered from surrounding particles of soil and vegetable chippage. These were cunningly wrought together, the whole structure silk-lined, and the characteristic trap-doors hung, one at either end. Thus, while varying her habit in so far as to build a surface tunnel instead of a subterranean one, Stothis preserved her defensive habit of erecting for herself a back door by which she could retreat in case of invasion at the front door.

The burrow of Stothis cenobita (Simon) is simply a rounded chamber underneath the surface, and closed by a trap-door, which differs in no particular, as far as I can observe, from the ordinary trap-door of the American Cteniza californica.

It is difficult to say what may be the enemies of the trap-door spider against which such ingenious architecture has been reared and such vigilant watch is exercised. But the quite general testimony is that these spiders leave their tubes at night and go forth in search of prey; or, as in other cases, open the lids of their tunnels and spread straggling lines near by, upon which passing insects are entangled and delayed long enough to allow the spiders to pounce upon them from their open caves. If we credit these accounts, we might infer that the enemies which the trap-door spiders most dread are not such as are abroad at night. Evidently the creatures are fearless at that time—a state of mind which doubtless results from their knowledge that they are comparatively free from their worst enemies. The enemies which they most dread may therefore be reasonably looked for among diurnal creatures, and not among those of nocturnal habits. Among these foes, at least one of the most formidable and irresistible is a diurnal insect, the female of the terrible digger wasp, which I do not doubt will be found to store trap-door spiders, as well as tarantulas and lycosids. There is no evidence known to me that Pepsis formosa invades the tunnel of the Mygalidæ, in order to dig them out. Such an act is not, indeed, beyond her powers; and, reasoning from the conduct of Elis 4-notata, it is highly probable. But we are not yet warranted in attributing the habit to her. Some lizard or mammal that might pull open the trap with its claws may be looked for as also a probable enemy against which trap-door spiders erect and defend their ingenious barrier.

At all events, the spider herself is well aware of these enemies. Abbé Sauvages invariably found, when he attempted to open the door of the nest of "the mason-spider" (Nemesia and Cteniza), that the mother was on guard, holding down the lid of her tunnel with great force. In his efforts to pull the trap-door up, the spider would jerk it down, and there would be an alternate opening and