Descriptive Zoology. 



FIG. 40. JUMPING 

 SPIDER. 



They suck the blood of insects, which they kill by means 

 of the poison introduced through the biting jaws. Their 

 bite is seldom serious to man, though one of the larger 

 spiders is said to kill small birds. There 

 is a strong sucking stomach which is 

 worked by special muscles. 



In addition to breathing by air tubes, 

 as in the case of insects, spiders also have 

 what are called lungs, or, from their 

 peculiar structure, "lung books." The 

 openings to these lungs are under the 

 abdomen. The cavity to which the 

 opening leads is somewhat like the inside 

 of a pocketbook, with a number of com- 

 partments. Blood flows around the out- 

 side of this lung book, and within the 

 plates or leaves of the "book." Thus the blood and the 

 air come near each other, separated only by a thin mem- 

 brane, and by the folding an increase of surface is secured. 

 This is the same general plan of all lungs and gills, but 

 the details of the plan are carried out in various ways. 



Like crustaceans, spiders molt, and one may often find 

 their cast skins, looking like dead spiders, but closer exami- 

 nation will reveal the difference. 



Spinning. One of the most interesting of the habits of 

 spiders is their web making. There is a great difference 

 among spiders in this regard. Some spiders spin very 

 little, leading a wandering life. Among these are tne 

 "jumping spiders," so named from their habit of creeping 

 stealthily close to their victims, and then suddenly pounc- 

 ing upon them. These forms are common, and their 

 habits are exceedingly interesting. But probably most 

 people are rather more familiar with the spiders that make 



