66 C. D. SOAR ON THE OCCURRENCE OF LARVAL WATER-MITES. 



capturing some more water-boatmen. A number of these were 

 brought home alive, as before, and this time I was successful in 

 getting some of the red globules attached to the legs and body of 

 the water-boatmen to become free-swimming in the nymph stage. 

 These again all turned out to be a species of the genus Hydrachna. 

 By comparing the size of the red larvae found on Notonecta 

 glauca in the autumn of 1898 with those found on the same form 

 at the same spot in the spring of 1899, I have come to the 

 conclusion that the water-mite larvae remain attached to their 

 hosts for a whole season — namely, from the summer of one year 

 until the spring of the next — and the fact that those I found in 

 the autumn did not undergo any alteration helps to strengthen 

 this opinion. 



I have further found two small yellow pear-shaped larval 

 water-mites on the larval form of a gnat, and also one on an 

 Ephemera larva, but I have been unable to rear them. 



I have found also that the water-scorpion, Nej^ta cinerea, is a 

 favourite host with some species. But I have not been able to 

 keep any alive long enough to find out to what species of Avater- 

 mite the larvae belong. In Epping Forest I took a specimen of 

 Ranatra, literally covered w^ith red water-mite parasites of all 

 sizes. This I succeeded in keeping alive until ten specimens 

 became free-swimming. They all turned out to be nymphs of 

 Hydrachna glohosa de Geer. 



But the most curious find, perhaps, in this connection, has 

 been a small fish from a pond on Earlswood Common with two 

 larval forms of water- mites attached, which I take to belong to 

 a species of Arrenurus. The accompanying figure ( x 10) shows 

 the position of the larvae on the fish, and it also illustrates the 

 general appearance of water-mite larvae when in the parasitic 

 stage on various aquatic creatures. I still have this interesting 

 specimen in spii-it with the red larvae attached. 



In concluding this short note 1 may say that I shall feel much 

 obliged if any of our members will kindly let me see any aquatic 

 animals they may find having parasitic water-mite larvae attached 

 to them. 



Jozirn. Quekett Microscopical C'Lv.b, Ser. 2, Vol. VIII., No. 48, April 1901. 



