ENEMIES AND THEIR INFLUENCE. 



405 



At one time twenty-eight of these spiders were kept under observation 

 in the observer's grounds. She visited them all frequently and found that 

 more than half the number, both males and females, had closed their doors 

 firmly. Some of the burrows were situated in bits of moss, and the moss 

 was so cunningly arranged over them that the most expert naturalist would 

 have found it difficult to tell where they were located. Mrs. Treat had 

 often tested the matter with her friends, to see if they could find one 

 of these concealed burrows, limiting their search to a few square inches 

 of space. But they rarely hit upon the right spot. Mrs. Treat kindly con- 

 tributed some of the coverings of these Tigrina burrows to my collection 



FIG. 340. A vestibule and dome of vegetable debris reared over the burrow of Lycosa tigrina. 

 Natural size. (From a cabinet specimen.) 



of aranead architecture. They are masses of vegetable debris, moss, grass 

 blades, chippage, dry twigs, the shell of an acorn, etc., arranged in an 

 irregular dome several inches in diameter across the base and an inch or 

 more in height. (See Fig. 340 and Figs. 341, 342.) 



What is the explanation of this care shown by Tigrina in the covering 



of its den in midsummer? The closure in winter is explained 

 The Ex- 



by the natural desire to protect the burrow from frost and 

 planation. * , 



snow. The closure during or previous to the moulting season is 



explained by the fact that the spider requires especial protection at a period 



