CHIGGERS — ^FARRELL 117 



length of the palpal claw is given in descriptions, the total length, 

 including the basal portion imbedded in the tibia, is used. The 

 tarsus, palp 5, is a short, thumblike segment attached ventrally 

 to the tibia at the base of the palpal claw and opposable to it. In 

 most species the tibia bears seven feathered setae — a large dorsal, 

 three near the apex, and three basal and ventral. Ventrally, near 

 the articulation with the tibia, the tarsus bears a striated seta, 

 or spur. 



On each galea is a seta which in different species varies in 

 form. It may be nude, forked, branched, or pectinate; or the 

 setules may arise on opposite edges of the shaft. The galeal seta 

 is an important taxonomic character. 



A chelicera is composed of two segments. The base is heavy, 

 usually angulate laterally, and may have punctae on its dorsal 

 surface. The distal segment is bladelike and curved. It bears 

 near the apex a dorsolateral tooth, which sometimes cannot be 

 found, and a larger ventrolateral tooth. 



The legs are composed of seven segments. By convention for 

 brevity the three pairs of legs are numbered with Roman num- 

 erals from anterior to posterior — I, II, and III. The segments 

 of the legs are numbered with Arabic numerals. However, the 

 two sets of numerals are not used together except in designating 

 drawings. The coxa, or basal segment articulating with the body, 

 is segment 1. The first freely movable segment, the trochanter, is 

 segment 2. The femur is divided into two parts. The more 

 proximal part is the basifemur, segment 3; and the more distal 

 part is the telofemur, segment 4. The genu is segment 5. The 

 tibia is segment 6. The most distal, terminal segment is number 

 7, the tarsus. On the leg segments are various specialized striated 

 setae and nonspecialized feathered setae. Some are constant 

 throughout the genus, others vary. All segments have non- 

 specialized setae with setules. On all segments except the coxae 

 and the trochanters these setae tend to lie parallel with the leg. 

 Those on the coxae extend posteriorly. Those on the trochanters 

 tend to curve ventrally and posteriorly around the segment. All 

 are nude on the side adjacent to the leg or the body ; the side op- 

 posite to the leg or body bears setules of slightly varying length 

 and form in different species. The segments may be marked with 

 punctae. 



On the coxa of leg I is a nonspecialized seta attached near the 

 anterior margin of the urstigmen. The trochanter bears a non- 

 specialized seta attached proximally at the anterodorsal margin, 

 curving posteriorly beneath the segment. The basifemur has a 



