112 



DK. A. C. Ol'DEMANS — A SHORT Sl'KYEY OF 



known as pseudostujmata, i. e., a pair of more or less cup-sbaped organs in 

 tlie neck, out of which emerges a sense-hair (in this case often club-shaped), 

 called the pseudostujmatic organ. — Sometimes they migrate by attaching 

 themselves to the hairs of small mammals (rats, mice, moles, weasels) or 

 flying insects, for which their fore-legs are specially adapted. When found 

 on animals they may be j)icked up with a moistened paint-brush ; but if they 

 occur on leaves, or ears of corn, the portion of the plant should be cut off and 

 placed bodily in spirits. 



found 

 their 



(7) Stomatostigmata is the name of a small group of Acari, 

 among dead or decaying leaves, on which they apparently feed ; for 

 mandibles are very short, but stout, and not pro- 

 trusive. Their body is well chitinised and therefore 

 more or less brown in colour. The arrangement of 

 the legs is very anomalous, all the coxae beino- 

 approximated. The presence of two pairs of 

 pseudosfigmata seems to show a remote relation to 

 the foregoing group. Their size is less than a 

 millimetre, and their stiomata lie between the first 

 and second pairs of mouth-parts. Their movements 

 are slow. Hitherto they have only been found in 

 the Northern Hemisphere. 



(8) To the large group of Prostigmata belong 

 various kinds of Acari, more or less related to one 

 another. They vary from one-fifth to ten milli- 

 metres in length. With only one or two exceptions 

 they are weak creatures, being white, yellowish, 

 rose or red in colour, rarely green or black. Their 

 stigmata, or the rudiments of these spiracles, lie 

 between the mandibles and the epistoma (a more or 

 less prominent frontal lobe). Their food consists 

 of plant-juices, blood, dead or living vegetable matter, or other smaller 

 animals ; the mouth-parts varying according to the diet. The presence of 

 one or two pairs of pseudostigmata shows their relation to the five foregoing 

 groups. The legs are generally placed in four groups of two. This group is 

 readily divided into three sections. 



(a) Prostigmata Eleutherengona are so called because their larvae are,, 

 with only a very few exceptions, free living. Hereto belong, among others, 

 the following families : — The Anystid^, or Spider Mites (fig. 10), are 

 swiftly running carnivorous Mites, closely resembling minute spiders, and of 

 a red colour ; they often occur in our houses, especially in garrets, but also 

 on difEerent plants ; and as they prey especially on Mites, which in our 



Fig. 9. — Zahidostonta denti- 

 cidatv.m (Scliraiik) ; fe- 

 male ; dorsal side and 

 mandible ; S = stigma ; 

 P=peritrema. — Original. 



