TYPICAL GROUP 3193 



it fits tightly into the upper end of the burrow, and it is said to be of the cork type. 

 Not unfrequently the spider digs a side gallery to this burrow, and shuts the aper- 

 ture of communication between the two by means of a second door. Then, in cases 

 of emergency, when the lid of the main entrance has been forced, the spider retreats 

 along the second branch and closes the door, so that the enemy, after exploring the 

 main tube and finding it empty, departs, believing the burrow to be tenautless. In 

 some instances, indeed, the secondary branch is made to communicate by a special 

 opening with the exterior, so that even if its internal aperture be discovered the 

 spider can still beat a retreat. It is by no means, however, an easy matter to force 

 open the lid in the first instance; for no sooner does the spider feel the attempt 

 being made, than it seizes the inner side of the door with the claws of its front legs, 

 and, firmly planting those of its hinder limbs in the silken walls of the burrow, re- 

 sists every effort to force an entrance. A few species have forsaken the ground and 

 taken to building their nests upon the trunks of trees, as shown in the opposite figure. 

 Some of these, like the South-African Moggridgea, and the Mascarene Myrtale, 

 avail themselves of natural irregularities in the surface and build silken tubes in the 

 crevices; then, chipping off pieces of bark and lichen, cover the white silk, so that 



FIELD SPIDERS (Segestria senoculata}. a. Female ; *. Male; c. Arrangement of eyes (enlarged). 



the tube and its door become invisible. The South- American Pseudidiops, frequent- 

 ing palm trees at Bahia, appears to excavate its own grooves in the bark by means 

 of the fangs, and the stout, short spines with which its mandibles are armed. 



In North Europe the only representative of this group is the genus Atypus, 

 which has been found in England and Ireland. This genus belongs to the family 

 Atypidce, differing from the rest of the section in possessing long maxillary proc- 

 esses on the coxae of the palp; and also in having six spinning mammillae. In- 

 stead of making a trapdoor nest, this spider spins a long silk tube, closed at the 

 ends, one half of which is buried in the earth, while the other lies loosely among 

 the grass or stones on the surface of the ground. When a fly or beetle alights on 

 this part of the web, the spider slowly and cautiously climbs to the spot, and, invis- 

 ible all the time to the insect, suddenly seizes it from within, and tearing away the 

 web drags its prey through the aperture, which is then repaired. 



The next section is that of the Arachnomorphce \ which includes the common 

 house and field spiders, and differs from the last in having the basal segment of the 

 mandible' vertical instead of horizontal, and the fang closing inward and back- 

 ward. There are generally six spinning mammillae, comprising an anterior two- 



