206 



JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVIII. 



Gr. H. Head of another more advanced embryo (enlarged.) 



I. The same embryo as G. & H. shown life size lying in its membranes. 



Dibrugarh, Assam, 

 28th May 1907. 



F. WALL, c.m.z.s., Major, i.m.s. 



No. XXIII.— NOTES ON A SOCIAL SPIDER, STEGODYPEUS 



SARASINORUM, Karsch. 



The genus Stegodyphus belongs to the family Eresidce, which latter is 

 divided off from most of the Indian Arachnomorphse by the possession of a 

 cribellum and its complementary organ the calamislrum. To save a special 

 reference to those unfamiliar with the anatomy of spiders, it will not be out of 

 place to state that the cribellum is a spinning plate placed immediately in front 

 of the spinners, and calani strum is a term applied to a single or double row of 

 short hairs on the protarsus of the fourth pair of legs. The organs are pecu- 

 liar to a group of Arachnomorphse including the Eresidce, and one organ is 

 invariably accompanied by the other. 



SUgodyphus sarasinorum is a social spider. The members of a colony 

 build a large saccular web mixed with oval passages, somewhat after the 

 pattern of a sponge, of a special dense texture. The special orgais above 

 described are no doubt particularly useful for weaving the peculiar web. The 

 spiders may be seen rapidly moving the hind pair of legs back and forwards 

 across the spinning mammillae and the cribellum, and turning out the peculiar 

 texture of web, of which their cities are constructed. 



The outside of the web is very viscous and even powerful insects can rarely 

 win free once they have struck it. 



