Vol. XX. January, ign. No. 2 



BIOLOGICAL BULLETIN 



CERTAIN HABITS, PARTICULARLY LIGHT REACTIONS, 

 OF A LITTORAL ARANEAD. 



THOS. H. MONTGOMERY, JR. 



This tiny beach-comber has been identified by Mr. Nathan 

 Banks as Grammonota inornata (Emert.), a species of theridiid, 

 for which I am much indebted to him. It lives at Woods Hole, 

 Mass., and in its vicinity, upon the sandy beaches along Vineyard 

 Sound and Buzzards Bay. Here it is found, however, in only 

 small scattered colonies for it occurs only on those sand beaches 

 where the eel grass, thrown up by the sea, lies in more or less 

 permanent lines upon the beach. Thus it does not exist upon 

 gravelly or rocky beaches, nor yet upon sandy beaches devoid 

 of the eel grass. The area of its distribution is limited to this 

 cast-up eel grass, from a line slightly above high tide level land- 

 ward as far as the patches of eel grass extend, a distance rarely 

 exceeding ten or twelve feet and determined more or less by the 

 degree of slope of the beach. In this peculiar home it obtains 

 perpetual moisture and darkness, and does not migrate further 

 up the beach nor into the salt marshes. In the same places 

 occur a variety of animal forms in great individual abundance. 

 Of this fauna the gammarids constitute the only truly marine 

 element, the others being mainly terrestrial forms: certain other 

 spiders, of which a drassid and the young of Trochosa cinerea 

 are most abundant, staphylinid and chrysomelid beetles, an 

 acarine, a pseudoscorpion and a chilopod. These are all normal 

 constituents of this fauna, not waifs drifted in by the sea. 1 



My interest was drawn to them by the observation that when 



J The elements of the "upper beach fauna" have been interestingly characterized 

 by Davenport, "The Animal Ecology of the Cold Spring Sand Spit," Dec. Publ. 

 Univ. Chicago, 1903. But he does not mention the particular species we are now 

 considering. 



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