V/ATER MITES. 



153 



CASE Genus Diplodontus {Duges). 



Nos. Diplodontus scapularis {Dug.^ Ann. Sc. Nat. 1834).— 10. Magnified 

 '°' '*' figure of larva ; 11. Ditto of perfect insect. 



This genus has the mandibles chelate, or quasi chelate, that is, 

 provided with a nipper or its equivalent. Other characters are 

 drawn from the different relative proportions of the joints of the 

 legs. The legs are ciliated, but the ciliae are so fine, and their 



Diplodontus scapularis, larva. 



Ditto, perfect insect. About the size of a sweet pea. 



motion so rapid, that although tolerably long, the naked eye 

 cannot see them when in motion, and the animal at the first 

 glance seems to move by some interior hidden mechanism. There 

 are several species of this genus. The colour of the present 

 species is red behind, interrupted in the middle, and black in 

 front, with some specks of red scattered through it. Duges places 

 this species in the genus Diplodontus. Koch removes it into his 

 genus Hygrobates. We have preferred to follow Dug^s. 



Genus Hydrochoreutes {Koch). 



Vos. Hydrochoreutes globulus (Hydrachna globulus, Mull.).—\2. Magnified 

 sketch of first stage of larva ; 13. Specimens of Belostoma grandis, 

 Linn, (the large water scorpion), with nymphs of Hydrachnidse ad- 

 hering to various parts of its body ; 14. Enlarged sketch of hinder part 

 of British water scorpion (Nepa cinerea), with nymphs of Hydrochoreutes 

 globulus adhering to its body ; 15. Sketch of nymph of ditto still more 



