SCIENCE-GOSSIP. 



193 



BRITISH FRESHWATER MITES. 

 By C. F. George, M.R.C.S. 



A XONOPSIS complanata Piersig was described 

 and figured by Midler more than a hundred 

 years ago, but since that time it has not been 

 delineated, nor has any description been given, so 

 far as I know, until that of Piersig 

 in 1893. He gave it the name of 

 Axonopsis bicolor, overlooking the 

 fact that Muller had already 

 figured, described and named it. 

 In the same year Koenike differen- 

 tiated it, giving Midler's name of 

 complanata and calling it Brachypoda 

 complanata. According to present 

 nomenclature it ranks as Axonopsis 

 complanata. No doubt, if Koch had 

 met with this mite he would have 

 placed it in his list of Arrenuri, as 

 in the case of other mites, which 

 have very properly been removed 

 out of that family. 



I first found Axonopsis complanata 

 about eighteen years ago, and have 

 still by me the 

 mounts I made at 

 that time. It seems 

 to be by no means 

 a common mite, and 

 I was pleased to be 

 able to send Mr. 

 Soar a living speci- 

 men last year. He 

 has since that time 

 found it himself, and 

 I have to thank him 

 for the figures ac- 

 companying this 

 article. This mite 

 is of an oval figure, 

 truncated in front 

 and only slightly 

 convex ; the skin is 

 chitinous, and under 

 the microscope it is 

 seen to be beauti- 

 fully marked, like an 

 extremely fine coat of mail. It is very distinctly 

 divided into three bands by colour, the first and 

 last blue (Muller says "deep green "), the middle 

 white and somewhat diaphanous ; the Y-shaped 

 portion is brilliantly white and opaque. In con- 

 sequence of its chitinous skin it mounts well in 

 balsam, and the beautiful transparent blue colour 

 of the anterior and posterior bands is well brought 

 December, 1898. — No. 55, Vol. V. 



ffm. 



Axonopsis complanata Piersig. 

 Fig. 1.— Upperside. Fig. 2. — Underside 



out. Like most mites, it must be examined alive 

 in order to appreciate its beauty. The palpi are 

 small and weak and do not form pincers, as in 

 Arrenurus. There are four genital discs on each 

 side of the sexual opening. The 

 eyes are black, and being placed 

 well forward, and near the outer 

 edge, are very conspicuous. On 

 each side, and near the outer edge, 

 is a depressed line, reminding one 

 of that of Arrenurus, only in this 

 case it is interrupted before and 

 behind. The anterior epimera are 

 also peculiar, projecting downwards 

 and beautifully serrated on their 

 outer edges in a manner I have not 

 noticed in any other water-mite. 



When once seen it is easily 

 recognized and cannot readily be 

 mistaken for any other mite. In 

 Mr. Soar's drawing, fig. 1 repre- 

 sents the upper surface. He has 

 not figured the palpi 

 and legs, but in 

 fig. 2 he shows these 

 attached in their 

 proper places. 



The deep green, 

 " saturate viridis," 

 mentioned by Muller, 

 is no doubt produced 

 by the yellowish 

 contents of the body 

 viewed through the 

 transparent blue of 

 the chitine. 



The diagnostic 

 characters of Axo- 

 nopsis complanata are : 

 (1) the three basal 

 joints of the first 

 pair of legs are not 

 thicker than the 

 others ; (2) the body 

 skin hard (chitin- 

 ous), like a coat of mail ; (3) all the tarsi furnished 

 with claws ; (4) body wider than high ; (5) four 

 genital cups on each side of the genital cleft. The 

 size is: length, 0-44 mm.; breadth, 032 mm. 

 Localities at present known in Britain : Lincolnshire, 

 and Staines, Middlesex. I do not know that any 

 other species of Axonopsis has yet been discovered. 

 Kivton-in-Lindsey. 



