Walckenaera atra. PI. XXI, fig. 215.
Walckenaera atra, Blackw., Linn. Trans., vol. xviii, p. 631;
— — Blackw., Annals and Mag. of Nat. Hist., second series, vol. ix,
p. 274,
Argus ater, "Walck., Hist. Nat. des Insect. Apt., tom. iv, p. 508.
Length of the female, ^th of an inch; length of the cephalo-thorax, ^nd, breadth, ^ th ;
breadth of the abdomen, ^th; length of an anterior leg, ^ th; length of a leg of the third
pair, 55th.
The two anterior eyes of the four intermediate ones forming the trapezoid are the
smallest of the eight. The cephalo-thorax is oval, convex, glossy, depressed on the sides,
which are marked with slight furrows converging towards an indentation in the medial line.
The falces are moderately strong, conical, armed with teeth on the inner surface, and inclined
towards the sternum, which is broad and heart-shaped. The maxillae incline towards the
lip, which is semicircular and prominent at the apex. The legs are provided with hairs; the
two superior tarsal claws are curved and pectinated, and the inferior one is inflected near its
base. The abdomen is oviform, thinly clothed with hairs, glossy, convex above, and projects
over the base of the cephalo-thorax.__The colour of this spider is black, with the exception
o f the falces, maxillae, legs and palpi, which are brown, the first two being much the darkest.
'The male is rather smaller than the female, and the anterior part of its cephalo-thorax,
where the eyes are situated, is prominent but obtuse, with an oblong indentation on each
side, extending backwards from the lateral eyes. The cubital and radial joints of its palpi
are short, the latter being much the stronger; the digital joint is oval, convex and hairy
externally, concave within, comprising the palpal organs, which are highly developed, complicated
in structure, with a long, black, very prominent, curved, filiform spine, enveloped in
membrane, originating about the middle of the outer side, and a short, straight, pointed one
at their extremity; their colour is reddish-brown.
Both sexes of Walckenaera atra, the males having the palpal organs in a perfect state of
development, were found in May, 1838, under stones in a moist pasture near Llanrwst.
In the ‘ Transactions of the Linnean Society,’ vol. xviii, p. 632, a conjecture is advanced
that this species may be the same as the Theridion acuminatum of M. Wider (Museum
Senckenbergianum, B. 1, p. 232, taf. 15, fig. 11); but well-marked differences in size,
structure, and colour, plainly show that they are distinct; and a comparison made between
Walckenaera atra and Argus Ucuspidatus, as suggested by M. Walckenaer in his ‘ Hist. Nat.
des Insect. Apt.’ tom. iv, p. 508, has been attended with a similar result.
Walckenaera aggeris. PI. XXI, fig. 216.
Walckenaera aggeris, Cambridge, Annals and Mag. of Nat. Hist., third series, vol. v,
p. 173.
Length of the female, ^th of an inch ; length of the cephalo-thorax, ^th, breadth, 5gth ;
breadth of the abdomen, 5\th ; length of a posterior leg, ^th ; length of a leg of the third
pair, -nzth.
The eyes, which are nearly equal in size, are disposed on the anterior part of the cephalo-
thorax, high above the frontal margin ; the four intermediate ones form a narrow, elongated
trapezoid, whose anterior side is the shortest ; and those of each lateral pair are seated obliquely
on a minute tubercle, and are contiguous. The cephalo-thorax is long, oval, convex, somewhat
glossy, without an indentation in the medial line, and has an oblong, vertical space
between the posterior and anterior intermediate pairs of eyes clothed with short hairs ; the
falces are small, conical, vertical, and armed with teeth on the inner surface ; the maxillæ are
greatly inclined towards the lip, which is semicircular and prominent at the apex ; and the
sternum is broad, convex, and heart-shaped. These parts are of a dark-brown hue, the falces
and /maxillæ being much the palest. The legs are slender, provided with hairs, and of a
yellowish-red colour, being paler at the articulation of the joints ; the fourth pair is the longest,
then the first, and the third pair is the shortest ; each tarsus is terminated by three claws ; the
two superior ones are curved and pectinated, and the inferior one is inflected near its .base.
The palpi are short and resemble the legs in colour. The abdomen, which has a black hue,
is oviform, glossy, sparingly clothed with hairs, convex above, and projects over the base of
the cephalo-thorax.
The sexes are similar in colour, but the male, which is rather the smaller, has an indentation
directed backwards from each lateral pair of eyes, and the oblong, vertical space
between the two intermediate pairs of eyes forming the trapezoid is densely covered with short
hairs. Its palpi are of a yellowish-red hue, with the exception of the digital joint and the
extremity of the radial joint, which have a brownish tint; the humeral joint is curved towards
the cephalo-thorax, and the radial, which is stronger than the cubital joint, is produced at its
extremity, in front, and has an acute apophysis on its outer side ; the digital joint is oval, with
a small lobe near its extremity, on the outer side ; it is convex and hairy externally, concave
within, comprising the palpal organs, which are highly developed, prominent, complicated in
structure, and of a reddish-brown colour.
Males and females of this spider were captured at Southport, in the summer of 1859, by
the Rev. O. P. Cambridge.