MICROSCOPIC OBJECTS. 86 



Fig. 171. Cheese-Mite (Acarus domesticus) , x 100. 

 Order Acarind. 



A large division of the Class Arachnida is comprised in the 

 Order Acarina, or Mites, of which this drawing may be taken 

 as one of the types. This well-known animal belongs to the 

 same family as the Itch-parasite (see fig. 175), the most evi- 

 dent difference in their structure being the length and posi- 

 tion of the legs ; the description of the family (Acarea) is as 

 follows: Head terminated in front by an emarginate labium 

 or single bifid process ; palpi adnate, or adherent to the labium, 

 difficultly distinguished; mandibles chelate; no distinct 

 ocelli; legs generally terminated by a vesicle or adherent 

 acetabulum and claws. The eggs are very numerous. The 

 best method to examine the characters of the parts of the 

 mouth, legs, &c., is simply to crush the Mite between thin 

 glass, and wash with a solution of potassa ; but to permanently 

 preserve them great care must be taken in crushing them. 

 After being well cleaned from the potassa, they may be dried 

 and mounted in balsam ; or they may be mounted in glycerine 

 without any previous preparation. 



Fig. 172. Parasite found on a Mason-bee (Trichodactylus 

 osmise), x 20. 



This Mite belongs to the same family as the Cheese-mite, 

 but to a different genus. The description is as follows : 

 Rostrum or beak short, with minute bristles ; fourth pair of 

 legs longer than the rest, without claws, and terminated by a 

 long bristle ; the rest with two claws ; legs pale red. Found 

 upon a species of Mason-bee. 



It may be mounted in the same manner as the preceding 

 species. Many of the Acari show well after being stained 

 with any of Judson's dyes, and then mounted in glycerine. 



