Clare Island Survey — Acarinida. 39 119 



Microthrombidium ramosum (George) var. similis nov. (PI. VIII fig. 37a.) 



This well-marked form is allied to M. sucidum (C. L. Koch), but differs 

 from it in the shape of the body papillae. A description, with figures, was 

 published by Dr. George in "The Naturalist " for the year 1909. 



Apparently the Irish form, of which a single specimen was found amongst 

 moss on Clare Island (June), differs from the type in the shape of the body 

 hairs, and in other details. 



The measurements of this variety are as follows : — length of the body, 

 including cephalothorax, 1126ju, and the breadth is about 640^. General 

 structure as in Microthrombidium. Crista normal. Eyes placed on the lateral 

 outline of the cephalothorax. The hair armature is very peculiar. The 

 shape of these hairs varies in different parts of the body, on the cephalothorax, 

 and the humeral regions— they are, mostly, pointed bristles all very strongly 

 spinous. Elsewhere on the animal the hairs have thickened extremities, 

 reaching their greatest development, in this respect, on the hinder region of 

 the body, where they are distinctly clavate with four, five, or six pointed lobes 

 or teeth at their extremities. The average length of these hairs, especially on 

 the hinder margin, is about 40//. The palps are short, length about 300,u ; 

 fourth segment wide at the base, and its appendage is large (45^ by 25^), 

 near its base is a strong " inferior spine." The legs are robust : length of 

 first pair about 71b'ju; tarsus sub-cylindrical widest near base, length 250^, 

 breadth (on side view) 90/x, length of tibia 125,u. 



In this variety the tessellated hairs are less closely set than in the type ; 

 they are not quite so clavate, and the extremities are less deeply branched. 

 The appendage of the last palp segment is shorter (in M. ramosum it measures 

 60,1* by 2,fy). 



Microthrombidium spinosum (Can.). 



A specimen of this distinct species was found amongst moss on the north- 

 east cliffs of Clare Island in September. 



All the measurements of this specimen are a little smaller than those 

 recorded by Berlese (16, p. 157), there is no doubt, however, that it is to be 

 referred here. There are two kinds of body spines, one kind having distinct 

 secondary hairs, and the other is plain and sword-like. 



Distribution. — Norway ; Italy ; Britain. 



Microthrombidium simulans Berl. 



Found in the West port district in April. 



This species may be recognized by the strongly fusiform body hairs. 

 There is only one stout external spine near the appendage of the last palp 

 segment. Here again the Irish specimens are smaller than the Italian. 



