144 BRITISH HYDRACHNID^. 



and Arrenurus papillaior, and others, by Max Krendowski, the 

 Russion Naturalist, in 1878. This will be found to be no easy 

 matter, for I have no doubt the larva of Nescea becomes parasitic 

 at a very early stage. The query is, on what does it become para- 

 sitic ? If the reader interested in this will turn to page 99 of 

 Science Gossip for 1870, an outline drawing will be found called 

 the Parasite of the Sand-fly, by W. Hanwell. If this drawing is 

 compared with my outline drawing from the life of the larva of 

 NescEU carnea, Fig. 3, g, I think the conclusion arrived at will be 

 that Mr. Hanwell's drawing represents also a larval form of an 

 Hydrachnid. 



We know by Krendowski's book that the larv^ of Arrenurus 

 papillator spend some part of their time out of water, because he 

 figures them on the wings of a Dragon-fly, These remarks will 

 show some of the difficulties to be encountered. Accident or 

 chance will, perhaps, reveal facts which have not been previously 

 noticed ; the great thing, I think, is first to become well acquain- 

 ted with the larval forms, and then to search every living form, 

 whether found in the water or out of it, that is likely to become a 

 host for these little creatures. Of course, I am now referring to 

 Nescea only. 



The Oribatidcs, which were so well worked out by Mr. Michael, 

 are not parasitic at all at any part of their life. By finding out 

 what the creatures fed on, keeping the cells moist, and the expen- 

 diture of a lot of patience and watchfulness, he was able success- 

 fully to trace their life-history from the egg to the perfect mite ; but 

 with the Hydrachnidce it is different, I have traced several differ- 

 ent species from the egg to the larva, and there I come to a full 

 stop. My friend Dr. George, of Kirton-Lindsey, has also reached 

 the same point with several mites, but like me has not, at present, 

 succeeded in going further, except in the case of an undetermined 

 species of Hydrachna which was found parasitic on Dytiscus 

 niarginalis. 



The metamorphoses of Nescea consist of four stages : first, 

 the egg, but I am not quite certain that all water mites deposit 

 eggs ; some genera may prove to be ovoviviparous, but it is certain 

 that the members of the genus Nescea do deposit eggs ; in con- 

 finement they lay them on the stalks and leaves of the water 



