306 



NATURAL HISTORY. 



air down to its diving-bell, coming up every now and 

 then to the surface for this purpose. 



520. I have already said enough of the Scorpions 

 (509), and on the second group of the Arachnida I will 

 spend but a few words. Among the Mites is the animal 

 which occasions the disease called the itch, an enlarged 

 representation of which you have in Fig. 239. It has an 

 oval body, a mouth armed with 

 bristles, and eight feet, four of 

 which have suckers at the end. 

 There is a great variety of mites 

 which are found on plants and an- 

 imals, and some live in the water, 

 swimming about with great free- 

 dom. The scarlet Mite of our gar- 

 dens has a most brilliant scarlet 

 color. The Harvest-men, so ap- 

 propriately called Father-long-legs, 

 as they have, perhaps, longer legs 

 than any other annual of any kind, 

 are mostly very agile. The Book 

 Scorpions, so called, are little 

 Arachnida which inhabit herbariums, old books, etc. 

 They are good runners, often going sidewise like crabs, 

 and they hunt the minute insects which are found in such 

 situations. 



Qtiestions. How do the Arachnida differ from insects? What is 

 said of their food ? What of their means of killing their prey ? What 

 is said of those which are parasitical ? What is said of the Scor- 

 pions ? What are the two groups of the Arachnida ? What are the 

 two chief purposes for which Spiders spin ? What other purposes are 

 sometimes accomplished by it ? What is said of the cocoons which 

 some Spiders spin ?- Describe the spinning apparatus of Spiders. 

 What is said of the compound character of the Spider's thread ? Why 

 is it not spun whole ? What is said of the mode of its attachment ? 

 Describe the foot of a Spider. What is the use of the combs in it ? 

 Describe its mode of repairing its web. What is known of the man- 

 ner in which Spiders transport themselves from one spot to another 



Fig. 239. Sarcoptes Scabiei, 

 or Acarus of the Itch. 



