[Footnote 136: This insect was probably not a true wasp, though belonging to an allied family; it may perhaps have been a _Pepsis_, certain species of which genus Mr. Bates informs me he has frequently seen near Santarem on the Amazon, hawking over the ground where the huge trap-door spiders lived, and suddenly pouncing down upon one of these creatures, often many times larger than themselves, when, after paralysing their victim with their sting, they would deliberately saw off the legs before dragging away the bodies!] Mr. Treadwell was quite as much impressed as Dr. Lanzwert with the belief that the bite of these spiders is fatal, but it does not appear that either of these gentlemen have obtained conclusive evidence in support of this allegation. I have occasionally been bitten by the trap-door spiders in South France, but have never experienced the slightest subsequent inconvenience, nor was there any trace of inflammation or poisoning about the punctures which they made. Mr. Blackwall[137] has made a very careful set of observations on this head, and has caused some of the largest species of British spiders to bite his finger and wrist until the blood flowed, without the slightest ill effects. He also inoculated himself at the same time with the poisonous secretion of the spider and with that of the wasp; when the latter wound became extremely painful, while the former was not perceptibly aggravated. Mr. Blackwall obtained the spiders' poison by causing a spider to seize a slip of clean glass with its mandibles, when a small quantity of a liquid showing a slightly acid reaction was deposited. [Footnote 137: Mr. J. Blackwall, _Researches in Zoology_, ed. 2, 1873; chapter on "The Poison of the Araneidea," pp. 240-256.] Mr. Treadwell informed me that these Californian trap-door spiders leave their nests in the daytime, and may be seen walking by the roadside, though they are always prepared to hurry back to their nests on the approach of danger. I received the spider which I have represented at fig. B, Pl. XV., p. 198 (_Cteniza Californica_), from this gentleman alive, and still within the remaining portion of her nest, on the 6th of July, 1873. She then had the legs and cephalothorax of a brownish-black, and the abdomen of a dull, uniform, dusky chocolate brown, but with an indistinct median line near the anterior end on the upper side, intersected at right angles by a shorter line. Mr. Treadwell said, however, that when captured, this spider was much darker, and of a pitchy black colour. The hairs all over the body were short, but especially so on the abdomen, which had the appearance of cloth or felt. This creature in many ways recalls _Cteniza fodiens_ of Corsica, and in a less degree the _Cteniza_ of Mentone and San Remo.