BURROWING HABITS OF SPIDERS. 31 



small abodes will be clustered about the old trapdoor. These vary greatly 

 in she, but all are quite perfect in form. Tlie smallest nest measured by 

 Miss Thomson was barely three inches in depth, yet this was fitted with 

 a diminutive circular door no larger than tlie nail of a lady's little finger. 

 The largest adult nest measured was twelve inches in depth. 



IX. 



Heretofore I have considered the nesting habits of spiders^ and the 

 influence of enemies upon their architecture (Vol. II., Chapter XIIL). 



Elsewhere I have tried to trace the relations between the nesting 

 Taren- habits of the two great tribes, Citigrades and Tunnelweavers.^ 

 ^ ^ A discovery lately made by Mr. W. A. Wagner, of Moscow, 



gives new interest to these statements and enables me to com- 

 plete the chain of resemblances pointed out. The connecting link between 

 the industry of the two tribes is found in Mr. Wagner's Tarentula opi- 

 phex,^ a Russian spider of the family Lycosoida.* The nesting habits 

 of this spider are thus described by Wagner. It was observed in numbers 

 in the Russian province of Orel, and dwells among the tufted vegetation 

 of fallow lands, its principal liabitation being fields of wheat and pota- 

 toes. The species is agile in movement, active in habit, and compara- 

 tively small in size, having a body length of less than one-half inch, ten 

 millimetres. (Figs. 12, 13.) The burrow is not deep, that of the adult 

 usually not exceeding two and a half inches ; it is enlarged at the bottom, 

 giving it a bottle shape (Fig. 15) ; is silk lined throughout, but the lining 

 is extremely thin except toward the entrance; the walls are smooth and 

 more carefully finished than usual with known Lycosids, as, for example, 

 Trochosa singoriensis. 



But the most remarkable and distinct feature is the covering of the 

 burrow, which is constructed after the well known type of the Trapdoor 



spielers. Figs. 14, 17, 18. This door consists of a single layer 

 Trapdoor ^f gj|j. covered externally with a coating of soil, whose pellets 

 ma ing ^^^^ bound together by a mesh of threads and sju'ead unequally 



upon the surface, being much thicker in front than behind. It 

 has the usual shape of the Trapdoor spider's door, something more than 

 semicircular, or a circular plate cut squarely across the end by which it 

 is hinged to the burrow. (See Figs. 17, 18.) Instead of being beveled 

 along the edge like the door of our Cteniza californica, and thus fitting 

 into the burrow like a cork into a bottle, it rests when closed upon the 

 surface edge of the burrow like a basket lid upon a basket. The front, 

 or entrance end, projects beyond the burrow (Figs. 15, IG), making a sort 



' Vol. I., Chapter XVIII. 



2 Pioceeii Acad. Nat. Sci., 1887, Philadelphia, page 377, sq. 



' Opifex ? 



* Bulletin Soc. Imper. des Naturalistes de Moscow, No. 4, 1890. 



