52 . AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



V. 



The trapdoor building habit is remarkable in its distribution over neai'ly 

 every part of the globe in tropical and semitropical regions. From what- 

 ever part reported, Europe, Africa, Asia, Australia, or North and 

 Architec- gQuth America, the nest shows the same peculiarities of structure, 

 ^. . and the architect appears to live in the same way. Even the habit 



of mimicking the surrounding surface by attaching sundrj' small 

 plants is cosmopolitan. Moggridge in his charming book has already made 

 us familiar with this form of mimicry in the European species ; it seems 

 also to characterize our southwestern trapdoors, and appears in Cambridge's 

 Idiops Colletti, a Burmese (India) spider.^ In the interesting description of 

 General Collett, which Mr. Cambridge publishes, it is stated that the upper 

 surface of the door is often covered with a dry black lichen growth. 

 There are generally a few withered grass blades worked into the edge of 

 the door, or into the edge of the mouth of the burrow, so as to form a 

 kind of semicircular fringe, which often catches a practiced eye and 

 leads to the detection of the hole. The grass blades are probably inserted 

 to aid in assimilating the outside of the door to its surroundings, a pur- 

 pose in which. General Collett opined, they certainly fail so far as the 

 human animal is concerned. In a few cases he noticed also grass blades 

 wrought into the general surface of the door, which in the dry 

 A Rude season, when the grass is everywhere withered, certainly aid in 

 „ , its concealment. But during the season when the adjacent grass 



is green one would think that j^ellow withered grass blades on or 

 near the burrow mouth would tend to make it conspicuous. I have con- 

 sidered at some length, Vol. II., pages 354, 355, the point thus raised in- 

 dependently by this intelligent observer, and its relation to so called 

 mimicry of environment. I need only add here that one can hardly be 

 asked to consider protection against human intelligence as a factor in the 

 action of a spider's mind. The hostile elements which influence it are of 

 quite another sort from the curiosity of a naturalist and the plundering of 

 a collector. 



VI. 



Since publishing my observations on the parasitic enemies of spiders 

 (A^ol. II., page 391) a number of facts have come to my hands which I 

 have thought well to embrace in these studies, and to add some 

 general conclusions suggested by the subject. Mr. George Carter 

 Bignell- has favored me with an account of the manner in which 

 Drassus lapidocolens Walckenaer was attacked bj^ an ichneumon (Sth Oc- 

 tober (1890). AVhile walking in the woods he noticed the spider suspended 

 by a silken drop thread from the bough of a large oak. Looking for the 



1 Proceed. Zool. Soc, Lond., 1889, page 37, pi. ii., Fig. 2. 



''■ 1 Clarence Place, Stonehouse, Devon, England. • 



