168 
PACIFIC SCIENCE, Vol. XIV, April I960 
MALE: Very similar to female in most re- 
spects except for form of genitalia. Genital 
sclerites crescentic in form, faintly punctate, 
bearing nine slender smooth setae each; para- 
genital sclerites completely absent. A small in- 
ternal corona bears only three pairs of setae 
which are readily visible, although others may 
be present. Only two pairs of acetabula present. 
Anus very small, lacking setae or sclerites. 
LARVA: Idiosoma 253-324 /x long to tip of 
scutal spine, 152-202 fx wide, length/width 
1.53-1.76; average 295 /x long, 179 ^ wide, 
length/width 1.65 (seven specimens). Scutum 
(Fig. 70) with four pairs of setae, the sensilla 
elongate, fusiform, bearing a number of barbs 
on both stalk and spindle. The spindle is col- 
lapsed in specimens mounted in Hyrax and 
sometimes even glycerine, but it is fully ex- 
panded in specimens in alcohol and Hoyers 
medium. The other three pairs of setae on the 
scutum are similar in form, although the an- 
terior setae (prosensilla) are somewhat longer 
than the others. Just anterior to the prosensilla, 
the scutum is drawn out into a very sharp tip, 
which in the living mite and in all preserved 
specimens seen by the writer is so closely ap- 
plied to the dorsum of the propodosoma that it 
appears to be rigidly fused with the latter. This 
is in marked contrast with the situation in most 
other Johnstonianidae in which the nasus lies 
more or less free of the dorsal wall of the propo- 
dosoma. However, in dissected material, and in 
material mounted in Hoyers medium, the nasus 
is seen to be a freely projecting spine. Behind 
the areolae is a transverse ridge or sharp decliv- 
ity, and behind this a rudimentary crista metop- 
ica. A few irregular panels and minute punctae 
are present. Ocular plates absent. Dorsal and 
marginal setae arising from individual sclerites, 
the alveoli lying in the anterior half of the 
sclerite. Shaft with a number of minute barbs. 
The dorsal setae at the anterior margin of the 
hysterosoma are appreciably smaller than the 
others. Dorsal and marginal setae numbering 
63 and 68 in the 2 specimens counted. Mem- 
branous cuticle mostly devoid of striae, although 
a few can be seen occasionally. 
Coxal setae numbering 2-1-2, all slender, 
tapering, and bearing a number of line barbs. 
The configuration of coxae I and II is markedly 
different from other genera of the Johnstoniani- 
dae, notably in the strongly transverse distal 
margins of I, the projecting lateral angles of I, 
and the exceptionally long medial margin of II. 
Supracoxal seta absent from I, coxal rings I and 
II both open dorsally, III with coxal ring 
very feebly developed dorsally. The urstigma is 
strongly protruded, the terminal portion hemi- 
spherical, attached to a stalk (Fig. 69). Mem- 
branous cuticle between coxae II and III with 
2 1 ventral and marginal setae in each of the two 
specimens checked; 6 setae between coxae III of 
right and left sides. The same two specimens 
had 30 and 35 ventral setae behind coxae III 
and a total of 93 and 103 postscutal and post- 
coxal setae. The setigerous sclerites (omitted 
from Fig. 66) from which the ventral setae arise 
are smaller and much less distinct than those on 
the dorsal surface, as are the setae themselves. 
Anal anlage a simple line. No Lassenia-organ 
could be found in any of the specimens studied. 
Base of gnathosoma without ventral setae 
(Fig. 74), supracoxal setae absent. A pair of 
setae laterally at base of rostrum, presumably the 
tritorostrals. Deutorostrals apparently absent, 
protorostrals slender, smooth. Velum simple, 
directed anteriorly. Chelicerae (Fig. 76) with 
ventral margin of distal membrane closely ap- 
plied to the dorsal surface of the tarsal claw (in 
Hoyers mounts, this membrane is distorted and 
lies free). Dorsal margin of tarsus with four 
sharp teeth visible under oil immersion. Palpi 
distinctly five-segmented, normally oriented. 
Trochanter a short cylinder without fenestra on 
anterior surface. Femur and patella with a single 
dorsal bihemipectinate seta; tibia with 3 slender 
setae plus the unidentate terminal odontus, 
which ends in a single point. Anterodorsal and 
posterodorsal setae of tibia with one to three 
delicate barbs, dorsal seta of tibia smooth. Tarsus 
of palp with solenidion at 0.09 p and three setae 
at 0.30, 0.60 and 0.82 d, these becoming progres- 
sively heavier toward the distal end. Beyond 
0.82, the tarsus is continued as a thin sharp 
blade. In addition there are four other pectinate 
normal setae as shown in the figure. Morpho- 
logically, the palp of Charadracarus is virtually 
identical with that of both Centrotrombidium 
and Diplothrombium; however the most disti- 
dorsal seta is not flattened as in those genera. 
