no AMERICAN SPIDERS 



ensure privacy, the trap door, for they represent a stock that was 

 probably capping burrows with doors long before many true-spider 

 emulators were evolved. The first description of this interesting 

 device was given by Patrick Browne, who in 1756 illustrated the 

 nest of a West Indian species in his Civil and Natural History of 

 Jamaica. A few years later the nests of Nemesia were described 

 from France, being likened to "little rabbit burrows lined with silk 

 and closed with a tightly fitting movable door." Although trap- 

 door spider nests continued to attract popular attention thereafter, 

 it was not until 1873, when J. Traherne Moggridge published his 

 careful studies on the habits of these animals, that any comprehen- 

 sive treatment was accorded them. 



Moggridge was able to distinguish four distinct types of nests 

 among the species he studied. The first was a simple tube, a cylin- 

 der closed with a thick, beveled door, which he termed the "cork 

 door"; the second was a simple tube closed with a thin or "wafer" 

 door; and the third type was a simple tube with a thin outer door 

 and a second door part way down. Moggridge's fourth classifica- 

 tion was the most complicated: a nest capped on the outside by a 

 thin door, and having an oblique side tunnel, connected with the 

 main tube, at the entrance of which was a trap door. Several other 

 types of nests have since been discovered in various parts of the 

 world, some of them much more complicated than those described 

 by Moggridge. Furthermore, the distinction between the cork 

 door and the wafer door, while valid enough in the extremes of 

 each type, gradually disappears as we examine long series of inter- 

 graded nests. 



The true trap-door spiders have developed a comblike rake of 

 large spines on the margins of their chelicerae, and this they employ 

 as a digging instrument. With its aid they are able to cut and scrape 

 away small particles of earth, which they mold into balls and carry 

 outside the burrow. They waterproof the walls of the tube by 

 applying a coating of saliva and earth, so that the surface becomes 

 smooth and firm. Then they apply a silken lining of variable thick- 

 ness and extent, in some cases not fully coating the burrow, while 

 in others covering the whole tunnel with a thick fabric. 



When the maturing spider outgrows its burrow, it enlarges the 

 domicile by cutting and scraping off bits of earth with its rake 

 and carrying them away from the site. Rocks embedded in the soil 

 may oblige the spider to pursue a tortuous course, or to dig a new 

 tunnel in a more favorable situation. It rarely deserts its burrow 



