316 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Stridu- 

 late. 



On this communication Professor Wood-Mason remarks that the sound 

 producing organs in Crustacea are paired organs, as in Scorpions, Mygahr. 



and Phasmidae ; that is to say, organs working independently of 



stridulat- eac jj o t] ier on ga^ s i(j e o f the body. They are differently seated 



, p or situated in various genera, but in all cases appear to consist 



of what may be called a scraper and a rasp, and the sound is 

 produced by rubbing together these two organs, which constitute the strid- 

 ulating apparatus. 



Professor Mason has also announced the discovery of stridulating organs 

 in Scorpions. This appeared from the study of the anatomy, but the matter 



was placed beyond doubt by observations made at Bombay. Two 

 orpions] ar g ii v i n g scorpions, procured from Hindustani conjurors, were 



fixed face to face on a light metal table and goaded into fury. 



At once they commenced to beat the air with their palps, and 

 simultaneously to emit sounds which were distinctly audible, not only to the 

 observer, but also to bystanders. They were heard above the flutter made 

 by the animals in their efforts to get free, and resembled the noise pro- 

 duced by continuously scraping with one's fingers bits of silk fabric or a 

 stiff tooth brush. The stridulating apparatus in this species is developed 

 on each side of the body; the scraper is situated upon the flat outer face 

 of the basal joint of the palp fingers, the rasp on the equally flat and pro- 

 duced inner face of the corresponding joint of the first pair of legs. 1 



It is thus found that from one extreme of the Arthropods, the Insecta, 

 where stridulation is frequent, through the Scorpions, and to the opposite 

 extreme, the Crustaceans, the habit of producing sounds, for whatever pur- 

 pose, is to be found. We therefore have a strong basis in analogy for the 

 belief that similar organs might be found among the spiders, animals tlint 

 rank between these extremes. 



XI. 



In point of fact, such organs have been found. The Swedish nat- 

 uralist Westring was the first to discover them, and his observations are 

 accessible to the general reader in his valuable work upon Swedish 

 Spiders. 2 He appends this observation to his description of " Theridion 

 serratipes." The abdomen of the male, around the cord by which it is 

 united to the thorax, is armed with a denticulated coat, whose use West- 

 ring had often puzzled over. At length he fortunately discov- 

 em j jj^ y-^g va i ve j s an instrument for stridulation. At the 

 base of the thorax the aranead is armed with transverse, most 

 delicately wrinkled striations, which are applied by the animal 

 for the producing of sound, as among insects. This sound Westring heard 

 when the spider was squeezed slightly ; then, either freely or when touched 



West- 



1 Proc. Ent, Soc. Lond., 1877, xviii. 



2 Aranete Svecicse, page 175. 



