92 Guide to AracJinida. 



Table- Mention must also be made here of the curious sound-producing 



99^^>d''^°^' organs which are found in many of the Tlicridiidac. These spiders 

 have the anterior part of the abdomen especially hollowed out and 

 hardened, the surface of this concavity being armed with teeth or 

 ridges which can be moved against the granular or striated surface 

 of the posterior end of the cephalothorax. In several of the 

 Agelenidae also an analogous structure occurs, but the structures 

 on the abdomen are rubbed against an enlarged tooth-like projec- 

 tion, which is present on the pedicel separating the cephalothorax 

 from the abdomen. 



Spiders are oviparous. They construct a " cocoon " (or several 

 cocoons) for the protection of the eggs, and this usually consists of 

 several layers of silk, the outermost coat in many cases being of 

 especial strength or thickness. Many species seem to give l)ut little 

 or no attention to their cocoon when once it has been completed. 

 Very often, however, the mother watches over it with extreme 

 solicitude until the young spiders emerge, and displays great 

 courage in its defence in times of danger. Special tents or cells 

 of silk for the reception of the cocoon are constructed by many of 

 the spiders which lead a wandering life, and by the tube-spinning 

 spiders {sec Wall-case 7). In these cases the mother shuts herself 

 up with the cocoon, remaining within on guard until the eggs 

 hatch. A large number of spiders which lead a predatory life 

 {L'l/cos'idae, etc.) carry the cocoon about with them, either in tlieir 

 chelicerae or attached to their spinnerets. 



The dispersal of the young of Araneids, which usually takes place 

 during the early part of the summer or in the autumn in this 

 country, is greatly helped by their aeronautic habits. The yoimg 

 spider climbs to the top of a shrub or other point of vantage and 

 turns its face in the direction from which the wind is blowing. 

 It then proceeds to straighten its legs, standing on the tips of them 

 and elevating its abdomen in the air. One or more threads of silk 

 now make their appearance, issuing from the spinnerets, and are 

 drawn out by the wind into long floating lines. At length the 

 spider lets go and is wafted away through the air, supported by its 

 air-ship of threads. In his " Naturalist's Voyage " Darwin makes 

 the following interesting observation on the ballooning habit of 

 spiders : " On several occasions, when the Beagle has been within 

 the mouth of the Plata, the rigging has been coated with the web 

 of the Gossamer Spider. One day (November 1st, 1832) I paid 

 particular attention to this subject. The weather had been fine 

 and clear, and in the morning tlie air was full of patches of 



