[ 143 ] 



Britisb 1b^^racbni^a^♦ 



By Chas. D. Soar. Part IV. Plate VI. 



THE next genus we will consider is Nes/EA. This is another 

 large genus, and when worked out will number as many 

 species as Arrenunts, if not more. Koch, in his Deutsch- 

 lands Crust., etc., describes and figures thirty-four species ; some 

 of these have since been removed to other genera. Koch himself, 

 in his Ubersicht, reduced the number to twenty-eight, making a 

 new genus for some, which he named Piona. We will notice 

 this genus later on. 



Several species of Nesaa are very common in England, some 

 being very small, almost as small as Axona versicolor, others are 

 as large as some species of Hydrachna. They also show a great 

 diversity of colour, greens, browns, yellows, and reds of all shades, 

 being represented by these little mites, one of the most beautiful 

 htvixg Nes(Ea coccinea (Y^O(ik\). As they are soft skinned,! have 

 not been able to mount any of them in Balsam successfully. The 

 integument always collapses in mounting, and the slides are thus 

 rendered useless. The best medium I have yet found in which 

 to mount Nescea is a 5 per cent, solution of formalin (this is a 

 formula given me by Mr. Rousselet). It unfortunately removes 

 the colour from the mite in the majority of cases (although not 

 always), but it preserves the shape and structure beautifully ; in 

 fact, the ventral side is often more distinct when mounted in the 

 medium than it is in life ; of course, if a coloured drawing has 

 been made from the life, it does not very much matter if the 

 colour of the mite is removed. The mount will show all the struc- 

 ture, but as a beautiful object for the microscope it is spoilt. 



Before we know very much about fresh water mites, the life 

 history of some will have to be worked out. The metamorphosis 

 from the egg to the imago will have to be carefully watched and 

 studied. For this we want a naturalist with the time, perseverance, 

 and ingenuity of Mr. Michael, who will do for the Hydrachnidcz 

 what he has done so thoroughly for the British Oribatidce ; in two 

 or three cases I know it has been done, as, e.g., A tax ypsilophora 

 by Van Beneden, in 1848 ; Atax Bonzi by Claparede, in 1868 ; 



