3192 THE JOINTED ANIMALS 



the hollows or upon the forked branches of trees. At night they issue forth in 

 search of food which for the most part consists of beetles and other insects; but they 

 will destroy and eat any living creature weak enough to be overpowered and trav- 

 elers report having found small birds in their clutches. When laid, the eggs are 

 wrapped in a strong cocoon, which the mother guards in her nest. 



The bird-eating spiders inhabiting the countries lying between India and 

 Queensland differ from those coming from Africa and America in possessing sound- 

 producing organs, which lie between the outer surface of the mandible and the 

 inner surface of the maxilla or basal segment of the palp. In one case, namely, 

 in the subfamily Selenocosmiince, the outer surface of the mandible is furnished 

 with spines, and the inner surface of the maxilla with a set of horny notes, of 

 varying thickness and length, which are thrown into a state of vibration by being 

 rubbed over the spikes on the mandible. This organ is equally well developed in 

 both males and females, and appears in the young soon after they emerge from the 

 eggs. When these spiders are irritated or alarmed, they raise themselves upon their 

 hind-legs and, by waving the palpi, scrape the keys against the spines on the man- 

 dibles and produce a sound which has been described as resembling the dropping of 

 shot upon a plate. It is probable that the sound thus produced acts for the benefit 

 of the spider in warning other creatures. In the second group ( Ornitkocto?imce) the 

 notes, formed of feathery hairs, are situated on the outer surface of the mandible, 

 and the spines on the inner surface of the maxilla. 



Nearly allied is the family Dipluridce, differing in having three well- developed 

 claws upon the feet, and the external spinning mammillae exceedingly long. Its 

 members differ in habits, spinning upon the ground wide sheet-like webs to insnare 

 prey. So far as the claw armature of the feet is concerned this family leads on to 

 the trapdoor spiders (Ctenvridtf), famed for the perfection of their architecture. 

 Although the species exhibit considerable variation in the perfection of their nests, 

 the method of work appears in all cases to be substantially the same. A deep tunnel 

 is first dug in the soil and then lined with silk to prevent the falling in of the loose 

 earth. Then, with the object of excluding enemies such as ants and wasps, as well 

 as to keep out rain, a lid, formed of layers of silk, strengthened with particles 

 of soil, is built over the aperture, and attached along one side of the wall of the 

 tube in such a manner that the elasticity of the silken hinge keeps the door nor- 

 mally closed. The outer surface of the 

 door is then covered, if necessary, with 

 fragments of moss, or with pieces of the 

 plants that grow in the vicinity of the 

 nest, so that when the door is closed it 

 matches its surroundings and becomes 

 practically invisible. In the genus Nemesia, 

 from the shores of the Mediterranean and 

 abundant in the Riviera, the lid is thin 

 and light and of the so-called wafer type; 



PAI,M TRAPDOOR SPIDER (Pseudidiops) but in the majority of cases it is thick 

 AND ITS NEST (natural size). an d heavy, with a beveled edge, so that 



