426 
PACIFIC SCIENCE, Vol. XI, October, 1957 
Johnstoniana George 1909 
ADULT: Large mites, idiosoma 1,000 to 
3,000 ijl in length, scutum a broad, roughly 
pentagonal plate with a prominent anterior 
spine, two pairs of slender sensilla and a fairly 
well- developed crista metopica. Lateral to the 
posterior sensilla is a group of several smooth 
setae, and in the posterior half of the plate 
usually one or two somewhat isolated setae. 
Ocular plates protruding, bicorneate; propo- 
dosoma lateral to scutum devoid of setae. 
Dorsal hysterosomal setae simple, smooth, 
borne on individual sclerites which may be 
elevated or not. Coxae I without supracoxal 
setae; intercoxal area with numerous smooth 
setae borne on individual sclerites; pars me- 
dialis coxae present. Genital and paragenital 
sclerites well developed, pregenital tubercle 
absent, three pairs of genital acetabula. Anal 
sclerites absent in J. latiscuta new species. 
Only two pairs of rostral setae, the deuto- 
rostrals apparently absent. Trochanter of palp 
not fenestrated, considerably longer anteriorly 
than posteriorly. Palpal tarsus with a single 
solenidion on posterior surface, and a number 
of prominent eupathidia. Palpal tibia with a 
simple terminal spiniform seta, and a single 
subterminal spiniform seta. Solenidial types 
Si and S 2 distinct, but s x and s 4 difficult to 
differentiate; s 2 relatively short, stout, marked 
with four longitudinal ridges. Eupathidia pres- 
ent on all segments of all legs including and 
beyond the telofemur. Vestigial setae present 
on patella I and II, but absent on tibia I and 
II. 
LARVA: Scutum bearing two pairs of sen- 
silla plus two pairs of other setae, all simple, 
smooth. Crista metopica present; anterior end 
of scutum drawn out into a frontal spine. 
Supracoxal setae absent. Urpore present. Tip 
of rostrum with only two pairs of setae, the 
deutorostrals apparently absent. Tarsus of 
palp with a single solenidion on posterior 
surface; typical eupathids absent, although 
the terminal setae of the tarsus are probably 
modified eupathids. Femora I to III incom- 
pletely divided dorsally in J. latiscuta. Patella 
I and II each with a vestigial seta dorsally, but 
tibia lacking vestigial setae. Dorsal eupathid 
of tarsus I with a basal companion seta. Tarsi 
of all legs with two unequal claws. 
remarks: The structure of the adult scu- 
tum as delineated by Berlese and reproduced 
by various authors is incorrect. Because of the 
very sharp downward flexure of the scutum 
between the posterior and anterior sensilla, 
the configuration of the scutum in undissected 
specimens is noticeably different from that 
seen in dissected specimens (Figs. 70, 86). 
Little is known of the biology of our one 
North American species except that it is ap- 
parently a cold stenothermal species found 
along mountain streams. J. errans (Johnston) 
1852 has larvae which are parasitic upon 
Tipulidiae. Cooreman (1952, p. 109) reported 
only one case in which he found this ordina- 
rily rare species in great numbers at one point 
along a small stream in Belgium. This rarity 
is apparently characteristic of the species de- 
scribed here, for the writer has seen only one 
female and a larva of J. latiscuta. Cooreman 
reported the capture of 44 females, but no 
males, which points up the fact that males 
have not yet been reported for this genus. 
Johnstoniana latiscuta new species 
female: Body of ovigerous female about 
1816 /d long to tip of scutum, 1330 /d wide, 
length/width 1.37; color in life a brilliant 
brick red (Fig. 65). Scutum (Figs. 70, 86) 
with two pairs of slender, smooth sensilla; 
plate divided into two portions, a broad ex- 
tensive posterior portion bearing the poste- 
rior sensilla and lateral and posterior to these 
six to eight setae on either side. The anterior 
portion is set off by a sharp declivity and bears 
only the anterior pair of sensilla, in front of 
which is a rounded knob produced ventrally 
into a sharp spine. Crista metopica well de- 
veloped in anterior half of scutum, feebly 
developed to absent in posterior half. Ocular 
plates protruding, prominently bicorneate; 
