152 A COURSE ON ZOOLOGY. 



like spiders that hold themselves in ambush, jumping 

 out on their prey as it passes, or even chasing it in its 

 flight. 



Two species the trap-door spider and the water-spider 

 are particularly curious in their habits, exercising great 

 ingenuity in the construction of their homes. The trap- 

 door spider is found in Africa, Italy, and the south of 

 France ; its form is much like that of the common spider. 

 It digs in a dry and sloping soil a cylindrical hole from 

 four to twelve inches deep, which it lines with a soft 

 coating of silk, and makes the entrance as round as if it 

 were traced with a compass. It then makes a thin but 

 strong and regular cover of clay, which it fixes to one edge 

 of its hole by means of an elastic hinge which allows the 

 door to be raised but at once closes it again. The out- 

 side of the door is rough and irregular, and cannot be 

 distinguished from the surrounding earth ; the inside is 

 smooth, excepting a few small notches on the edge oppo- 

 site the hinge. If we try to lift the door of a hole con- 

 taining a trap-door spider, we feel a strong resistance, 

 sometimes so great as to make the raising of the door a 

 matter of considerable difficulty. After having gently 

 opened the door we see that the little creature has put 

 the hooks of two of his legs in the small notches we 

 have mentioned, and with the other feet is clinging to 

 the walls of his tube, and that it is he who has been 

 holding shut the door. 



The water-spider, although it can live under water, 

 possesses, like all other arachnida, aerial respiration, 

 and it procures its supply of air in an interesting man- 

 ner. Coming to the surface of the water it puts out its 

 abdomen, which is covered with a sticky, greasy matter, 

 then, suddenly plunging in, it carries down a bubble of 



