502 THE POPULAR SCIENCE MONTHLY. 



MITES, TICKS, AND OTHEE ACAKL 



By E. K. LELAND, 



THE acari constitute a large order of minute animals, including 

 mites, ticks, itch insects, etc, with which, in some of their forms, 

 every one is more or less familiar, though, owing to their small size 

 and obscure ways of living, but little is known of their structure and 

 habits. They are often spoken of as insects, but are by scientific 

 classification separated from the true insects, the most marked dis- 

 tinction being the possession of eight legs instead of six. Usually 

 they are furnished with a suctorial apparatus. They are parasitic on 

 both the animal and vegetable kingdoms. No class of animals is free 

 from them. They prey upon each other ; insects are infested with 

 and support them at the cost of their lives ; they attach themselves 

 to fish and cold-blooded reptiles, and colonize on the whole range of 

 birds and mammals. Some live under the skin, burrowing in the 

 muscles ; others dig corridors beneath the ejndermis ; while others, 

 again, wander only on the surface. They are found in the lungs, air- 

 passages, and intestinal canals of vertebrates. They are very prolific, 

 and, though small, awkward, and slow-moving, they are transferred 

 in a surprising way, often suddenly appearing about houses in enor- 

 mous numbers, infesting plants and domesticated animals, or swarming 

 on articles of food. Sometimes, especially in the tropics, they inflict 

 considerable suffering ; but it is probable that, on the whole, they are 

 beneficial to man. A few directly injure him, and none directly bene- 

 fit him, but indirectly they do him service by preying, as will be seen, 

 on insect-pests and by acting as scavengers. The number of species 

 in this family is so great as to forbid any detailed description, or even 

 the merest mention of all of them. For the most part they are seldom 

 seen except by those who make them a study. But a brief account of 

 what is known about those of them that come into relations with man 

 closely enough to afiect his comfort and welfare, may be of interest 

 and value. 



The species thus referred to are found in the following classes : 1. 

 Spinning and harvest mites, red spiders, etc. {Tromhidnnm) ; 2. In- 

 sect mite-parasites, sometimes called ticks ( Gamasidce) ; 3. True 

 ticks (Ixodidas) ; 4. Cheese and sugar mites, itch mites, etc. {Acari- 

 dce) — the portion of the family commonly included under the name 

 acari. 



The spinning mites, like their relatives the spiders, can spin 

 webs. They are of small size and semi-transparent. The most com- 

 mon is the red mite (Fig. 1), Tetranychus telarius, so well known 

 to all who have the care of house plants. It is one twentieth of an 

 inch long, yellowish, with two red spots on the sides, though its color 



