ANATOMY. 61 



phagus sciurinus, and usually there are rather more 

 hairs on the tarsus than on the other joints of the leg ; 

 but hairs are not, as a rule, very numerous on the legs 

 of the Tyroglyphidse ; an exception, however, is found 

 in the tarsi of Glycyphagus spinipes, which are densely 

 clothed with minute, extremely fine hairs. 



The males of the genera Tyroglyphus, Alewrobius, 

 Ohortoglyphus, etc., usually have a pair of suckers on 

 the inner side of the tarsus of each fourth leg, doubt- 

 less for the purpose of holding the female. 



The Ambulacra of the Tyroglyphidse consist almost 

 invariably of a single claw, either with or without a 

 caroncle or sucker. In. the foreign genus Hemisar- 

 voptfts, Ligniere, the claw is entirely absent, and is re- 

 placed by a sucker on a long pedicle. Kramer, how- 

 ever, considers that the single species of which this 

 genus consists does not belong to the Tyroglyphidae at 

 all, but .to the Sarcoptidae, sub-family Canestrininse. 

 Personally I have not ever seen the species, but from 

 the published literature I should be inclined to suppose 

 that Kramer's view is likely to be correct. The claw 

 is usually largest in such genera as RhizoglypJms, 

 where the caroncle is entirely absent. In that genus 

 it is very strong and much curved; in the two hind 

 pairs of legs of Histiostoma, which also is without 

 caroncles, the claw is almost straight. In some genera, 

 such as Glycyphagus, or perhaps I should rather say 

 the typical portion of that genus, composed of such 

 creatures as G. spinipes and G. domesticus, the claw is 

 almost rudimentary and has the effect of arising from 

 the centre of the caroncle without any other direct 

 communication with the tarsus ; but in reality very 

 minute tendons pass from the tarsal muscles to the base 

 of the claw, which is generally enlarged or provided 

 with projections at right angles to the length of the 

 claw. In the genus Lentungula the claws of the first 

 and second pairs of legs, which are very minute, are 

 mounted upon long, flexible peduncles, which can be 

 bent in all directions at the will of the creature; the 



