Charadracarus new genus, Charadracarinae new subfamily 
(Acari, Johnstonianidae), 
and the Status of Typhlothrombium Berlese 1910 
Irwin M. Newell 1 
Berlese and Leon ardi (1901: 17) described 
a mite from Argentina which they named 
Trombidium histricinum. The species was de- 
scribed as follows: Dark cinnabar, large, broad- 
shouldered, flattened dorsally, rounded posteri- 
orly. Body setae 25 /x long, sharp, spiniform, cin- 
nabar, dense. Cephalothorax nude, except in 
median portion. Crista metopica linear, a tuber- 
cular elevation posteriorly, containing the areo- 
lae. Palpal tarsus long, clavate, extending beyond 
the claw; tibia with an ornate series of six spines 
along the internal surface, a single terminal 
claw. Legs rather long, setae plumose, irregu- 
larly ornate. Tarsus I at least five times longer 
than broad. I was unable to see eyes by any 
means. Adult 3 mm. long. One specimen col- 
lected at St. Pedro Mission, Argentina. (Author’s 
translation.) No figures were given. 
Berlese (1910: 358) designated Trombidium 
histricinum as type species of the new genus 
Typhlothrombium. The original description of 
the genus was very brief, including little beyond 
the original description of the type species, ex- 
cept for the fact that a nasus was present. Char- 
acteristics set forth in the original description 
of the genotype which are at variance with de- 
scriptions of the two species subsequently placed 
in this genus ( Typhlothrombium grandjeani 
Andre 1930, Typhlothrombium aelleni Coore- 
man 1954) are: the dark red color, flattened 
dorsum, the very short setae (25 /*), the dense- 
ness of the chaetotaxy, the presence of a well- 
developed ctenidium, the slender form of tarsi 
I, and the large size of the body (3 mm.). The 
differences are so considerable as to leave no 
doubt that Typhlothrombium grandjeani and 
Typhlothrombium aelleni have nothing to do, at 
the generic level, with Typhlothrombium his- 
1 University of California, Riverside, California. 
Manuscript received March 17, 1959- 
tricinum. The only unusual feature pointed out 
up to this time which is shared by Typhlo- 
thrombium histricinum on the one hand and 
T. grandjeani and T. aelleni on the other hand 
is the absence of the eyes. This is not a very sig- 
nificant point of similarity, however, in light of 
the many points of difference noted above. The 
genus Typhlothrombium Berlese 1910 therefore 
must be restricted to the type species. The family 
status of Typhlothrombium is uncertain, but it 
is provisionally retained in the Trombidiidae. 
The author has had the opportunity of study- 
ing a form very similar to Typhlothrombium 
grandjeani Andre, which occurs in southern 
California. A second North American species, 
from Point Barrow, Alaska, has been collected 
by Dr. Paul Hurd of the University of California 
at Berkeley. Finally, through the courtesy of 
Dr. Marc Andre, I have been able to study type 
material of Typhlothrombium grandjeani . These 
three species, together with Typhlothrombium 
aelleni Cooreman comprise a natural group of 
congeners, Charadracarus new genus, with C. 
hurdi new species as the genotype. 
The genus is unusual in several important 
respects although it is obviously closely related 
to the Johnstonianidae. While there are impor- 
tant points of difference between the species of 
Charadracarus and other members of the John- 
stonianidae, it appears that these differences can 
be suitably recognized by establishing a new 
subfamily within the Johnstonianidae. 
ACKNOWLEDGMENTS 
This study was carried out under a research 
grant (NSF G-4251) from the National Science 
Foundation to the University of California at 
Riverside. The illustrations are by Mari Riess of 
the University of California at Riverside. In the 
figures, the scales are marked in 10 /x units. 
156 
