27.6 ARACHNIDA—ARANEAE CHAP. 
ego-bag, which, since its construction, has been so situated as to 
be out of the view of the spider. Peckham found that spiders 
of the genus TZheridion, accustomed to the sight of their 
cocoons, readily recognised them by that sense when removed 
to a distance. 
The most keen-sighted of the spider tribe are undoubtedly the 
Attidae, or Leaping-spiders. The little black and white striped 
Wall-spider, Salticus scenicus, is probably a familiar object to most 
of our readers, and a very little observation of its movements, like 
those of a cat stalking a bird, will convince the observer that its 
visual powers are wonderfully keen and accurate. Its attitude of 
“attention” on sighting its prey, its stealthy manceuvring to 
approach it unobserved, and the unerring certainty of its final 
leap, are very interesting to witness. 
It is somewhat noticeable that both in the Epeiridae and in 
the Attidae the two portions of the body, cephalothorax and 
abdomen, have more than the usual freedom of independent 
motion. In the Orb-weavers this gives play to the spinnerets in 
binding up a captured insect, but in the Leaping-spiders it allows 
of the rapid directing of the large anterior eyes towards the 
quarry, as it continually alters its position. 
Professor and Mrs. Peckham of Wisconsin’ performed some 
interesting experiments to ascertain the sensitiveness of the 
spider's eye to colour. Freely communicating compartments of 
cufferently coloured glass were constructed, and spiders were con- 
fined in them, when it was found that red was the most and blue 
the least attractive hue. This agrees well with what Lubbock 
found to be the case with ants, but those insects displayed a greater 
antipathy for blue and not so marked a preference for red. 
HEARING.—Most of our knowledge about the auditory sense 
of spiders is due to experiments performed by C. V. Boys, and 
repeated by Professor and Mrs. Peckham. 
The spider usually responds to the stimulus in one of two 
ways ; it either raises its front legs, extending them in the direc- 
tion of the sound, or it allows itself to drop suddenly, as though 
in alarm. It was only in the case of the Epeiridae that any 
results were obtained, and these spiders were more sensitive to 
low than to high notes. Now, as M‘Cook points out, it is 
1 J. Morph. (Boston, U.S.A.) i., 1887, p. 403. 
2 Nature, xxiii., 1880, p. 149. 
