ARTHROPODA 



177 



Class 3. Myriapoda. — The Myriafoda (Gr. murics^ ten thou- 

 sand; podes, feet) have a head with paired antennae and mandibles, 

 many similar body segments bearing leglike appendages, tracheae, 

 and excretory (Malpighian) tubules which open into the intestine. 

 The Millipeds are wormlike in appearance with about three hundred 

 segments, to each of which is attached two pairs of appendages. 



Fig. 8 1 . Peripatus. (From Pearse, General Zoology. Courtesy of Henry Holt & Co.) 



Very few of them are injurious to agriculture. Julus is a crop 

 destroyer. Centipedes have but one pair of appendages for each 

 segment. The large tropical centipedes {Scolopendra) are reported 

 to be extremely venomous and their bite may even be fatal to man. 

 They reach a length of eighteen inches, are carnivorous and able to 

 kill insects almost instantly. South American Indians use them as 

 food. The house centipede {Scutigera forceps) feeds on flies, cock- 

 roaches, and bed-bugs and since it is not very poisonous to man, is 

 of considerable economic importance. 



Class 4. Hexapoda. (Insecta.) (Gr. hex., six; ?Ln6.pous, foot.) 

 — We live in the Age of Insects, and struggle with them for the 

 possession of the earth. Not only physical and chemical agencies, 

 but all available natural enemies must be utilized in order to keep 

 the insects under control. They devour our foodstuffs, destroy our 

 animal friends and still prevent us from claiming important new 

 territory. The number of species of insects outnumbers those of 

 all other animals taken together, and the number of individuals is 

 incalculable. Little is known about the histology, embryology or 

 physiology of insects, but all that we do know has shown that they 

 are of tremendous importance economically. Interesting studies 

 of their habits have shown that insects are highly developed and 

 specialized in their behavior. 



The Insecta have three well-defined regions, the head, thorax and 



