SCIENCE- G OSSIP 



BRITISH FRESHWATER MITES. 



By Charles D. Soar, FJRJff.S, 



(Continued from Vol. VI., page 365. ) 



4. Atax intermedins Koenike. 



Body. — Female about 0.68 ram. long. Breadth 

 about 0.56 mm. Colour dirty yellow, with dark 

 brown markings on the dorsal surface. Oval in 

 shape. In some specimens the marginal line bends 

 a little inwards on the posterior portion. It is with- 

 out the two papillae we find in Atax crassipes. 



LEGS. — First pah about 0.80 mm. Fourth 

 pair about 1.0 mm. All of the legs are fairly 

 thick, not the first pah- only as in A. eras- 

 All are well supplied with hairs, par- 



Fig. 1. Ata.r intermedins. Tarsus. 



ticularly the fourth pair. The first pah have the 

 usual sword hairs common to members of this 

 genus, but they are not so strong and powerful as 

 in A. crassipes. One of the best points of identity 

 in this species is the double claw (fig. 1). There are 

 two claws to each of the tarsi, though I have only 

 drawn one, so that its structure can be easily seen. 



Epimera. — In four groups. 



Palpi. — About 0.28 mm. long. The first seg- 

 ments are very thick. On the last segment but one 

 are two or three small pegs, but very insignificant 

 when compared with those we find on the same 

 segment of A. crassipes. 



Genital Area. — Composed of two pairs of 

 plates, the upper pair having each two discs, the 

 lower three discs (fig. 2). The plates are very 



Fig. 2. A. intermedins. Geuital plates of female ? 



similar to those of Atax taverneri, except the 

 arrangement of the three discs on each lower plate, 

 which in the case of this mite are placed in the 

 form of an angle. 



Male. — Is a little smaller than female, but 

 showing similar structure, except that in the genital 

 area we find two plates instead of the four. In the 

 female each plate has five discs. 



Localities. — I have as yet only taken this mite 

 in the Norfolk Broads. I found two females and 

 one male, also several nymphs in the gills of fresh- 



water mussels ; but no doubt it is to be found at 

 other places where Anodonta is common. 



5. Atax bonzi Claparede, 1868. 



This mite is very much like the preceding 

 species. In fact, so much so that it does not 

 require any particular description, so long as the 

 differences between the two are pointed out for 

 identification. It is about the same size, but the 

 legs are much thinner and with less hairs. 

 Although it has two claws to each foot, each claw 

 is single, not double, as we found in. A. intermedins. 

 The genital area is also much the same in appear- 

 ance, excepting that the three discs on the lower 

 plates of the female are arranged more in a row, 

 and do not form such an angle as shown on fig. 2. 



Localities. — I found several females of this 

 species also in the gills of some freshwater 

 mussels in the Norfolk Broads. There appears to 

 be two species of these mussels in the Broads : one, 

 Anodonta eygnea. and another : but this mite 

 appears to favour both, for I found some in each kind. 



6. Atax ypsilophorus Bonz. 



This mite has a number of discs on each of the 

 genital plates, which are situated at the extreme 

 margins of the body. 



Localities. — This species was taken by myself 

 in the Norfolk Broads ; but unfortunately I did 

 not make any drawing of it, therefore fuller 

 description must await further captures, unless 

 some of our readers are kind enough to send me 

 specimens. It is parasitic on freshwater mussels, 

 like the two preceding species. 



GENUS COCHLEOPHORTTS PIERSIG. 



The characteristics of this genus differ very little 

 from the preceding one. The palpi are small and 

 thin, also less in width than the first pair of legs. 

 The genital plates are nearer the epimera, and not 

 so much on the extreme margin of the body as we 

 found in Atax. A number of discs are found on 

 each plate, though there is one species of Atax 

 which also has a number of discs on each genital 

 plate, viz. Atax ypsilophorus Bonz. 



1. (ochleopliorus spinipes Miiller. 



Body. — Female about 1.20 mm. in length. Width 

 about 1.0 mm. Colour a pale greenish-yellow, 

 with brown markings on the dorsal surface, in the 

 centre of which is a yellow T-shaped mark. The 

 dermal glands on the dorsal surface are also very 

 prominent. Eyes very conspicuous, and near margin 

 of bodv. 



