Natural Enemies. 



129 



but six legs which, though easily visible when the animal 

 first attaches itself, become more or less obsolete and in- 

 visible as it swells and enlarges, though a careful examin- 

 ation will generally reveal them at the anterior end of the 

 body. The mite, therefore, more often presents to the 

 ordinary observer a bright red, swollen, ovoid body, so 

 immovable and firmly attached by its minute jaws, that 

 those who are not aware of its nature might easily be led 

 into believing it a natural growth or excrescence. In 

 fact, it attacks the locust precisely as the different wood- 

 ticks attack man and the lower mammals. 



This mite belongs to the genus Astoma, briefly charac- 

 terized by Latreille for a very similar mite (Astoma para- 

 siticum) which affects the common House-fly and several 

 other insects. The specific name locustarum was first pro- 

 posed for it by B. D. Walsh,* but Dr. LeBaron afterwards 

 gave it the name of Atoma gryttaria,\ in connection with 

 the following more detailed description : 



They are of an oblong, oval form, moderately convex and having 

 an uneven surface, produced by four shallow depressions on the 

 upper side, the two larger near the middle, and the others behind 

 them. The body has also two slight constrictions, giving it the 

 appearance of being divided into three segments ; but the im- 

 pressions are superficial and only visible at the sides. The whole 

 surface is finely striate, under the microscope, the strise running in 

 a waving transverse direction. The mouth-organs appear to be 

 reduced to their minimum of development. The only part visible, 

 externally, is a minute papilla, on each side of which are two 

 bristles, the inner of which is stouter, tapering to an acute point, 

 and curved inwards, or toward its fellow of the opposite side. 

 They differ from the majority of Acarides in having but six legs, 

 and these, being of but little use in so stationary a creature, are 



* Practical Entomologist, I, p. 126. 



t LeBaron"s2ndIll. Ent. Rep., 1872, p.156. The author employs the term Atoma, 

 which, though at first so employed by Latreille, is corrected to Astoma in his "Gen- 

 era Crustaceorum et Insectorum," I, p. 162, (1806). . 

 9 



