water mites 39 



Collection and Preservation. 



Water mites are to be found not only in standing water, 

 ranging in size from our largest lochs to narrow ditches, but 

 also in rivers and streams. Many can be found among the 

 aquatic vegetation by sweeping with a fine net attached to a 

 stick or a long cord. A small bottle or tube at the end of the 

 net allows the collector to ascertain readily the nature of the 

 booty. Other species may be found creeping over the 

 surface of the mud or among submerged stones. On the gills 

 of fresh-water mussels certain species of Unionicola are only 

 to be found. Attention paid to water insects like Notonecta, 

 Nepa, Dytiscus, Corixa, etc., and even to Dragonflies, will 

 reward the observer with the so-called larval parasitic stage 

 of water mites. Observations on the migrations of insects 

 known to be hosts of water-mite larvae might yield much 

 valuable information to account for the distribution of 

 species whose existence in certain areas has been accounted 

 for as glazidlrelikt. 



The most useful medium for killing and preserving water 

 mites is a mixture of glycerine, water, and acetic acid, in the 

 proportion of u, 6, and 3 respectively After a few days 

 mites placed in this solution resume their normal shape and 

 for long remain soft. The use of glycerine is at present to 

 be avoided, but a preparation consisting of thymol (1 vol. of 

 abs. alcohol sol.), 2 per cent, glacial acetic acid (1 vol.), 

 absolute alcohol (2 vols.), and distilled water (4 vols.) may 

 be employed with equally good results (Koenike's formula). 

 Formaline is, if possible, to be avoided, as it is very apt .to 

 render material unsuitable for examination. Seventy per 

 cent, alcohol would be better. Tubes containing material 

 should be promptly labelled with date and place of capture. 1 



1 For labelling, a slip of paper with data written in pencil, but 

 preferably with waterproof ink, should be inserted in the storage tube. 

 Where glycerine is used, I find the most durable labels are slips 

 of tracing-paper on which details are written with waterproof ink. Heat 

 from lamp or fire dries the ink, and slightly melts the waxy surface of 

 the paper, allowing the ink to sink further in. Placed in glycerine, 

 the paper becomes transparent, leaving the black writing to stand out 

 prominently. Such labels are very durable. Pencil or ordinary 

 ink becomes obliterated very quickly. 



