150 CLASS-BOOK OF ZOOLOGY. 



the strength with which they resist the action of wind 

 and weather. 



§ 647. Those Spiders which construct webs, are pro- 

 vided, at their posterior extremity, with four or six warts, 

 containing one thousand openings. 



§ 648. From these openings descend one thousand 

 threads, that unite and become a single line, which is so 

 fine that one hundred of them are not as thick as a human 

 hair. 



§ 649. Spider-webs, like silk, have been manufactured 

 into stockings and gloves. However, the manufacture of 

 silk to any considerable extent, from the webs of Spiders, 

 is impracticable ; as, in order to obtain one pound of such 

 silk, the webs of 600,000 Spiders would be required. 



§ 650. Spiders feed on living animals, particularly in- 

 sects. Being quarrelsome and cruel, they attack and kill 

 each other ; and on that account they lead, like misan- 

 thropes, a solitary life. 



§ 651. Scorpions (Scorpio) have a considerable resem- 

 blance to Crabs in their form and mode of life ; for, like 

 them, they have eight feet, two pincers, and a hard crusta- 

 ceous shell, which they cast yearly. 



§ 652. Scorpions are found in the temperate as well as 

 the tropical regions of the globe, living under stones and 

 in damp places, and even in houses. 



§ 653. Their food consists of insects, which they seize 

 with one of their pincers, inflicting at the same time a 

 mortal wound with their venomous sting, which is also 

 dangerous to man. 



§ 654. Crabs (Cancer) are of a slender, square, triangu- 

 lar, or globular form, and generally inhabit the seas and 

 rivers. They breathe by means of gills, which are found 

 on the thighs of the pectoral feet. 



§ 655. Crabs have two pincers, eight feet, two jointed 

 antennae, and are covered with a calcareous shell, which 

 they cast off every year at the end of spring. 



§ 656. The power of reproduction in Crabs is aston- 

 ishing. A foot or a pincer, of which they have been de- 

 prived, is reproduced, generally with the new shell, but 

 also at other times. They will of themselves cast off 



