V. 



Musical Boxes in Spiders. 



APART from such unavoidable sounds as the buzzing which results 

 from the rapid vibration of wings, or the pattering made by the 

 striking of feet against hard surfaces, nearly all the animals belonging 

 to the group which zoologists call the Arthropoda are mute. 



But in each of the great divisions of this class, namely in the 

 Crustacea (Crabs and Shrimps), the Arachnida (Scorpions and 

 Spiders), the Myriopoda (Centipedes and Millipedes), and the Insecta 

 (Flies and Beetles), there are some species which are provided with 

 organs specially set apart for producing sounds. These sounds are 

 produced in various ways ; but in most cases they result from the 

 rubbing together of two mutually roughened surfaces. In the common 

 house-cricket, for instance, the under surface of the wings of the front 

 pair is furnished with a fine saw, and the familiar chirrup of this insect 

 is caused by the rubbing of one wing over the other in such a manner 

 that the saw of the one that is uppermost scrapes over the ridge-like 

 nervures of the other lying beneath. 



Organs constructed on the same principle exist in some Milli- 

 pedes, some Crabs, several Beetles, and a few Spiders. Their 

 presence in spiders was first announced in 1843 by Westring, who 

 found them in the males of some small European species, which were 

 then referred to Theridium. The instrument consists of a finely-toothed 

 area upon the forepart of the abdominal or hinder region of the body ; 

 and the sound is produced by the scraping of the teeth against a set 

 of grooves upon the hinder end of the carapace or dorsal shield, 

 which covers the forepart of the body. About forty years later 

 Mr. Campbell published the description of an analogous organ in 

 some species of an allied genus, Lephthyphantes. But in the latter the 

 stridulating organ is connected with the mouth-parts, and consists of 

 a series of ridges, accompanied by a knob, upon the outer surface of the 

 mandible, and of a corresponding series upon the adjacent surface of 

 the third segment of the palp. Moreover, in all other spiders in 

 which similar instruments have been found, they are placed in sub- 

 stantially the same position. Consequently, a few words to explain 

 the structure of the jaws and their relation to one another may be 

 added, in order that the working of the organs now to be described 

 may be made intelligible to all readers. 



