286 ENTOMOLOGICAL SOCIETY 



The trochanter, or the second joint, is the shortest. It is 

 somewhat curved backward, narrow at the base, and wider at the 

 apex, and is of a somewhat pear-shaped form. The first tro- 

 chanter is provided in all the genera of the Rhipistomidag at the 

 posterior border with a broad, pointed, spinous process, which is 

 directed backward. This armature is absent in all genera of the 

 family of Ixodidae. In Ixodes, however, a small pointed tubercle 

 is noticed on the first trochanter. 



The femur, or third joint, is of varying relative length, but 

 always the smallest of the four articulations that follow the tro 

 chanter ; it is composed of two joints which have coalesced, and 

 the original dividing suture is more or less distinctly noticeable 

 in all species. The coalescence, however, is so perfect that there 

 is no real articulation beween the small basal and the distal parts. 



The tibia, the fourth joint, also varies in relative size both in 

 the legs of the same individual and in those in the different 

 genera. 



The next joint, the metatarsus, is generally the shortest of the 

 four joints following the trochanter. Of special interest is the 

 sixth joint, the tarsus. This is also formed by the coalescence 

 of two joints into one, but this is only distinct in the last three 

 pairs. Here the division is sometimes very marked, but in some 

 genera, as in Amblyomma, there is also a faint trace of a former 

 division in the tarsus of the Jirst pair. 



This joint differs in shape from the other joints of the leg, for 

 while these are evenly cylindrical arid somewhat clavate that is, 

 their distal ends a little thicker the tarsus tapers gradually 

 towards the tip, and its underside is provided with two more or 

 less prominent teeth or claws, which are placed one at the apex 

 and the other a little further back. An exception, however, in 

 this respect, as well as in the whole shape of this joint, is the tarsus 

 of the first pair in all genera, for there it appears laterally flattened 

 and becoming broader towards the last third of its length, when 

 it quite abruptly narrows down to the end. 



The tarsus of the first legs in all Antistomata (but not in the 

 Catastomata) is provided on its dorsal surface, near the tip, with 

 a peculiar organ, which Haller* considers an organ of hearing. 



*Haller, Vorlaufige Bemerk. liber d. Gehororgan der Ixoden-Zool. 

 Anz., 1881, pp. 165, 166, with figure. 



