A nest was made near one of our tramways, and to get to the trees the ants had to cross the rails, over which the wagons were continually passing and repassing.  Every time they came along a number of ants were crushed to death.  They persevered in crossing for some time, but at last set to work and tunnelled underneath each rail.  One day, when the wagons were not running, I stopped up the tunnels with stones; but although great numbers carrying leaves were thus cut off from the nest, they would not cross the rails, but set to work making fresh tunnels underneath them.  Apparently an order had gone forth, or a general understanding been come to, that the rails were not to be crossed.

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SOME WONDERFUL SPIDERS

(FROM A JOURNAL OF RESEARCHES, ETC.)

BY CHARLES DARWIN.

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The number of spiders, in proportion to other insects, is here compared with England very much larger; perhaps more so than with any other division of the articulate animals.  The variety of species among the jumping spiders appears almost infinite.  The genus, or rather family of Epeira, is here characterized by many singular forms; some species have pointed coriaceous shells, others enlarged and spiny tibiae.  Every path in the forest is barricaded with the strong yellow web of a species belonging to the same division with the Epeira clavipes of Fabricius, which was formerly said by Sloane to make, in the West Indies, webs so strong as to catch birds.  A small and pretty kind of spider, with very long forelegs, and which appears to belong to an undescribed genus, lives as a parasite on almost every one of these webs.  I suppose it is too insignificant to be noticed by the great Epeira, and is therefore allowed to prey on the minute insects, which, adhering to the lines, would, otherwise be wasted.  When frightened, this little spider either feigns death by extending its front legs, or suddenly drops from the web.  A large Epeira of the same division with Epeira tuberculata and conica is extremely common, especially in dry situations.  Its web, which is generally placed among the great leaves of the common agave, is sometimes strengthened near the centre by a pair or even four zigzag ribbons, which connect two adjoining rays.  When any large insect, as a grasshopper or wasp, is caught, the spider by a dexterous movement, makes it revolve very rapidly, and at the same time emitting a band of threads from its spinners, soon envelops its prey in a case like the cocoon of a silk worm.  The spider now examines the powerless victim, and gives the fatal bite on the hinder part of its thorax; then retreating, patiently waits till the poison has taken effect.  The virulence of this poison may be judged from the fact that in half a minute I opened the mesh, and found a large wasp quite lifeless.  This Epeira always stands with its head downwards near the centre