INTRODUCTION. 



Mites, or Acari, belong to the class Arachnida, which also includes 

 the spiders, scorpions, harvestmen, etc. Arachnids differ from 

 Insects in having eight legs instead of six. The chief feature 

 distinguishing mites from other Arachnids is that they have only- 

 three pairs of legs when they are hatched from the egg, the fourth 

 pair being added later. Most Acari are very small and their body 

 is usually unsegmented. There is great diversity of structure 

 in the group. 



The names of the principal families are given below, those dealt 

 with in the present pamphlet being printed in heavier type than 

 the others. Ticks are not included, but it is hoped that another 

 pamphlet dealing with them may be issued later. 



The parasitic mites found on domestic animals differ greatly in 

 habits. They may burrow or tunnel in the skin (e.g., Sarcoptes) 

 or live in the sebaceous glands (e.g., Demodex), or cause crusts or 

 scabs on the surface of the skin (e.g., Psoroptes). The feather 

 mites, or Analgesidae, as their popular name implies, live in the 

 plumage of birds, and some even live in the interior of the quills, 

 as do also some Trombidiidae (Syringophilus, etc.). The Listro- 

 phoridae and ^some Trombidiid mites {Myobia) cling to the hairs of 

 mammals. Many of the Gamasidae live in the nests of rodents, 

 but may also sometimes be found on their bodies. 



