44 
Avgas persiciis 
the femora is div'ided from the remainder of the article by a joint-like 
constriction, constituting a pseudo-article (the trochanterin of Lahille). 
The coxae (see PI. I, fig. 2, cx. i, ii, Hi and iv) have a more or less 
triangular contour, with rounded angles, and are set into apertures of 
corresponding outline which penetrate the ventral body wall. The fold of 
chitin which forms the actual joint between the coxa and the body wall 
extends, in part, for some little distance into the body cavity, and serves 
as a means of attachment for the coxal muscles. As previously stated, 
the coxae are not absolutely immobile. They are capable of a limited 
amount of adduction and abduction, a condition which is facilitated by 
the presence of the coxal and supracoxal folds. The trochanter {tch.) is the 
shortest article of the leg. Its form is roughly cylindrical and the length 
barely exceeds the breadth. The articulation of the trochanter with the 
coxa is such as to limit its movement to a plane which is more or less 
parallel to the ventral surface of the body. The three following articles, 
the femur (fm.), tibia (tb.) and j^^’otarsiis (pts.), are of approximately 
equal length, that of the femur being slightly increased by the presence of 
the pseudo-article at its proximal end. Each of these articles is smallest 
at the proximal end the diameter increasing gradually to a maximum at 
the distal extremity. The greatest freedom of movement is found at the 
articulation of the femur with the trochanter which forms a universal 
joint; the remaining articulations only allow of movement in a single 
plane. The tarsi (ts.) are about equal in length to the three preceding 
articles, but instead of expanding distally, they become suddenly 
attenuated near the free extremity, the place of attenuation being 
marked, particularly in the case of the first two pairs of legs, by 
a pronounced hump. The tarsi of the fii’st pair of legs are distinguished 
by the presence of Haller’s organ {Hal. org.). The pulvillia are arti¬ 
culated with the reduced extremities of the tarsi. All the articles of 
the legs, with the exception of the coxae and trochanters, are slightly 
flattened in a dorso-ventral direction, and with the same exception they 
bear a small number of fine, short hairs which are arranged in scanty, 
longitudinal rows. The pulvillia (see PI. VI, fig. 26) of the adult 
and nymph consist of a small segment or caruncle (car.) of irregular 
form, upon the slightly expanded extremity of which the claws are 
articulated. The collapsible pad, which is so conspicuous a feature of 
the pulvillia of the Ixoclidae, is only represented by a slight puckering 
of the parts surrounding the bases of the claws {pv. in fig. 26). In the 
larva, on the other hand, the pulvillium is well developed (see fig. 27), 
and all the parts which exist in that of the Ixodidae can be recognised. 
