download pdf

175
Platyarthrus Hoffmannseggi, Brandt.
(PI. LXXVI, fig. 2.)
Platyarfhnis Hoffmannseggi, Branch, Consp. monogr. Crust. Onisc. p. 12, PI. 4. fig. 10.
Syn : Itea crassicornis, Koch.
Jyphloniscus Steinii, Schobl.
Specific Characters. - Body broadly oval, and much depressed, with the
dorsal face smooth, though slightly granulose all over. Cephalon partly flanked
by the side-plates of 1 st segment of mesosome, frontal edge arcuate and minutely
crenulated, lateral lobes narrowly rounded at the tip, and obliquely produced in
front, edges crenulated. Side-plates of mesosome rather large, lamellar, sub-
contiguous, 1st pair the largest, edges finely denticulate. Metasome scarcely ex-
ceeding '/a f the length of the mesosome, the 2 anterior segments very small,
epimeral plates of the 3 succeeding segments narrow, recurved ; last segment
comparatively short, triangular, resembling
that in Philuscia muscorum. Anten-
nulse with the basal joint fully as long as the other 2 combined. Antennae
scarcely exceeding }
/s of the length of the body, and hirsute all over with short
hairs; last peduncular joint very large and dilated, flagellum
shorter than that
joint, and lanceolate in form. Legs densely spinous inside, propodal joint coni-
cal in form. Uropoda with the basal part rather large, oblong,
outer ramus
about same length and lanceolate in form, inner ramus much narrower, and
scarcely extending to the middle of the outer. Colour pure white. Length of
adult female 3 mm.
Remarks. This peculiar Oniscid was first described under the above
name by Brandt. It was subsequently observed by Schobl, who regarded it as
new, and described it as Typhlonisc.us Steinii. Koch too does not seems to have
been aware of Brandt's description, and hence recorded it under another name,
viz., Itea crassicornis, referring it wrongly to his genus Jtea, which is identical
with Trichoniscus of Brandt. It is an easily recognizable Oniscoid, being easily
distinguished by its pale, flat body, the strongly built antenna?, and the total ab-
sence of visual organs.
Occurrence. In Norway this form has not yet been observed; but,
as it
is widely distributed over the northern part of Europa, I cannot doubt that, on
a closer investigation, it will be found to exist in this country also. Its pe-
culiar habits and occurrence within ants' nests may also be the cause of its having
hitherto escaped the attention of Norwegian zoologists. The figures here given
are from specimens kindly sent to me from the Zoological Museum in Copenhagen.
Distribution. Denmark, Germany Holland, Britain, France, Bohemia,
Austria, Tyrol, Helvetia.