Charadracarus n. gen. — N ewell 
157 
CHARADRACARINAE new subfamily 
Since the genus Charadracarus is the only one 
known at the present time, the characteristics of 
the subfamily are the same as those of the genus. 
The most significant characters which separate 
the Charadracarinae from the other subfamilies 
of the Johnstonianidae are: ( 1 ) the presence of 
only two pairs of genital acetabula in the adult, 
( 2 ) the single pair of genital sclerites (the 
paragenitals apparently being absent), ( 3 ) the 
absence of tracheae in both larvae and adult, 
(4) the undivided femur in legs III and IV of 
the adult and in leg III of the larva. The ab- 
sence of corneae and ocular plates is important, 
but the same condition has been reported in 
Crossothromhium parkhousei Womersley 1939, 
as well as in Typhlothrombium histricinum 
( Berlese and Leonardi ) 1901. 
The habits are not well known. The larvae 
are almost certainly of the self-detaching type 
and may be simple predators on small soil or- 
ganisms. The predatory nature of the larvae is 
surmised from the fact that they have never 
been found on a host, in combination with the 
fact that they show a great variation in size in 
the soil, indicating that they are feeding and 
growing. The larvae are almost colorless and 
adults are pale yellow to white — not dark brown 
or red like other Johnstonianidae. The writer 
has found them in large numbers in the winter 
under black oak ( Quercus kelloggii Newberry) 
in the mountain ranges of southern California. 
This oak usually grows in situations where soil 
moisture is more abundant than in other places, 
either in deep gullies or on north slopes, etc. 
Thus, while Charadracarus deviates more than 
other known Johnstonianidae from a subaquatic 
habitat, their ecological distribution is still rela- 
tively restricted. At the type locality of C. deli- 
tescens, hundreds of individuals were found 
under the oaks on the south side of a gully, but 
the species was totally absent from the northern 
side of the gully where only the coast live oak 
( Quercus agrifolia Nee) was found. 
Charadracarus new genus 
ADULTS: Idiosoma rather small, less than 1 
mm. in length; color pale yellow to white. 
Scutum with sensilla bearing a bulblike expan- 
sion in known forms; prosensilla more than 
one half as long as the sensilla, but markedly 
different from the sensilla, more closely resem- 
bling the other setae of the scutum. Anterior 
end of scutum drawn out into a long sharp spine 
closely appressed to the dorsal wall of the propo- 
dosoma. Dorsum of gnathosoma without spi- 
racular openings. No major tracheal trunks 
associated with cheliceral apodemes internally. 
Dorsum of propodosoma with no setae lateral 
to scutum. Corneae and eyes absent. Chaetotaxy 
of hysterosoma simple, setae only a little more 
numerous than in the larva. Genital opening 
bordered by only one pair of sclerites; para- 
genital sclerites absent. Two pairs of genital 
acetabula in both sexes. Pregenital tubercle ab- 
sent. Anus lying in the completely undifferenti- 
ated ventral cuticle between the genital opening 
and the posterior end of the body; no trace of 
anal sclerites or anal setae. Anterior wall of 
trochanter of palp with no trace of a fenestra. 
Palpal tibia with or, usually, without paradont. 
Solenidion of palpal tarsus basal in position. 
Eupathidia confined to tarsi I and II, absent 
from tarsi III and IV and all other segments of 
the legs. Supracoxal setae absent from gnathos- 
oma and coxa I; vestigial setae also completely 
absent. Solenidiai and s 2 only moderately dif- 
ferentiated but s 2 distinctly shorter and straighter 
than Si. S 3 and S 4 convergent in form, S 4 only 
a little heavier and with a little more distinct 
internal structure in typical cases, but inter- 
mediate forms exist which are unassignable to 
either category. 
LARVA: Scutum with four pairs of setae, the 
prosensilla more like the other setae of the 
scutum than like the sensilla. Nasus sharp, 
closely appressed to the dorsal surface of the 
propodosoma. Crista metopica feebly developed, 
confined to the portion of the scutum behind 
the areae sensilligerae. Ocular plates absent. 
Coxal setae numbering 2-1-2. Urstigma present 
and well developed. A number of setae in the 
membranous cuticle between coxae II and III. 
Anal sclerites absent. Deutorostral setae appar- 
ently absent, rostrum with only the proto- and 
tritorostrals. Anterior wall of palpal trochanter 
not fenestrated. Terminal setae of palpal tar- 
sus not typically eupathidiform, but flattened 
and heavy walled. Tarsal eupathidia numbering 
