NEW PARASITIC MITES. 773 



the single specimen liave been destroyed by the caustic potash 

 used in prepai'ing it. It seems probable, however, that this 

 absence is natural for in general appearance the mite is very 

 like a Rhinonyssas, and the spines may be reduced or almost 

 suppressed in the latter genus. There is a fully-developed larva 

 inside the specimen and it resembles the parent in having only a 

 few hairs on the legs. The claws of this h\rva ai-ewell developed 

 and strongly curved. 



Length (with capitulum) '53 mm. 



Host : The above description is based on a single specimen 

 labelled " Sur un Oiseau de Madagascar." Professor E. L. 

 Trouessart's collection. 



Genus LiPONYSSUS Kolenati. 



The species of this genus are found both on birds and mammals. 

 Only the species that I have been able to examine personally 

 are included in the key given below. A number of species are 

 not in our collection, and these have been left out. Two dorsal 

 shields are present in the nymphal stages of LijMvyssus, whereas 

 there is usuallv a single undivided dorsal shield in the adults. 

 In the adult females of a few species, however, there are two 

 dorsal shields as in the nymphs : for instance in L. viator^ sp. n., 

 where they are shaped exactly as in tjie nymphs of certain other 

 species. The adult females can always be distinguished by the 

 presence of separate sternal and genito-ventral plates on 

 the venter, and by the delicate fan-shaped or semi-circular 

 genital operculum situated at the front end of the latter plate. 



Key to the females of the species of the genus Lvponyssus 

 present in the British Museum Collection : — 



C Dorsum with two sliields 2. 



^■] 



(. Dorsum with a single shield , 8. 



("Posterior of the two dorsal shields verj' small 3. 



(. Posterior of the two dorsal shields fairly large 4. 



f Anterior dorsal shield small and separated from the 



I minute posterior shield by a considerable space ... L. serpent iumHivat, 



I Anterior dorsal shield rather long and only separated 



i^ from the posterior one bj^ a short space L. natricis Gerv. 



r Sternal plate quite short, the two posterior hairs on it 

 ^\ long. Anterior spur on second coxa short L. viator, a]), n. 



\. Sternal plate longer 5. 



C Posterior margin of sternal plate stronglj' chitinised . 6. 



(.Posterior margin of sternal plate weakly chitinised... 7. 



f Posterior dorsal shield with only three pairs of fairly 



j long hairs i. chiropteralis, 



6.<; nom. nov. 



1 Posterior dorsal shield \\ith a number of fairly long 

 L hairs L. nyassce, sp. n. 



