87 



SOME BRITISH EARTHMITES. 



Tro m bidiidae . * 



(plate IV.) 



C. F. GEORGE, 



Kirton-in-Lindsev . 



Ix 1877, Professor Kramer initiated a genus, or sub-genus of 

 Trombidium, which he named Ottonia, the distinction being 

 based on the fact that the eyes had not the long petiole as in 

 Trombidium, but were rather embedded in the skin of the 

 cephalothorax. I take it that the mite I am about to describe 

 belongs to the sub-genus, I call it therefore Ottonia ramosa. 

 So far as I know, it has not previously been figured or recorded. 

 It is a rather small mite for a Trombidium. Mr. Soar gives the 

 length of the body as 1.28 mm., and the breadth .38 mm. It 

 is of a rose madder colour with a dash of pink, very beautiful ; 

 in shape, it is something like fiiliginosum, but not quite so elon- 

 gate, the distal end of the fourth joint of the palpus is furnished 

 with two distinct claws, (see Plate IV., figure b). In holoser- 

 iceum and fiiliginosum, it is single (see in ' The Naturalist ' for 

 1908, figures on page 333 and Plate XLIL). 



This peculiarity seems to be the rule in the smaller species 

 of Trombidium. The eyes are each provided with two ocelli 

 and are embedded in the skin of the cephalothorax, the distal 

 joint of the fore legs is larger than the others, club-shaped, and 

 flattened sideways (see figure d). The other legs are formed on 

 the same plan as the mites already described ; they have not 

 the peculiar footpad found in fuliginosum. The female genital 

 aperture has the usual copulatory discs, three on each side 

 (figure c). The papillae on the body are most remarkable ; 

 they are all rather coarsely barbed, but many on the back, and 

 especially those at the sides and posterior part of the body, in 

 addition to the barbs, have the ends divided into two, three, or 

 more branches (hence the name ramosa). These branches are 

 almost as thick as the main stem, and look more or less like 

 tassels (see figure e., f. and o). The papillae are not placed so 

 close together as in some mites, and seem to be arranged in 

 irregular longitudinal rows. When the mite is mounted in 

 Canada balsam, without too long preparation, the colour is 

 retained to a considerable extent in the papillae, which then 



* For pre\ious papers see the 1907 volume of ' The Naturalist.' 

 1909 March i. 



