On the spider genus Racata Millidge, 1995, with the description of three new species (Araneae, Linyphiidae)
Author
Tanasevitch, Andrei V.
text
Revue suisse de Zoologie
2019
2019-03-31
126
1
53
59
journal article
10.5281/zenodo.2619518
f8f43b16-9b08-446f-b4dd-e8e1fe8b78e9
0035-418
2619518
Racata
Millidge, 1995
Type
species:
Racata grata
Millidge, 1995
, by original designation and monotypy.
Diagnosis:
Members of the genus
Racata
can be easily recognised by the “micronetine”-like chaetotaxy, by the highly developed convector and by the presence of a panicle-shaped median membrane in the palpal organ. Females are distinguished by a distinct epigynal cavity, which is often surrounded by sclerotized swellings, and by mostly helical copulatory ducts. The genus contains medium-sized spiders with a total length of 1.45-1.75, which are characterized by the following combination of somatic and genitalic characters:
1) Carapace unmodified in both sexes, eyes somewhat enlarged, cephalic pits (= sulci) absent.
2) Chaetotaxy formula: TiI: 2-1-1-0; II: 2-0-1-0, III- IV: 2-0-0-0; MtI-IV without spines; MtIV without trichobothrium; TmI 0.20-0.30.
3) Palpal tibia simple, unmodified.
4) Distal part of cymbium narrowed.
5) Convector highly developed and sclerotized.
6) Median membrane panicle-shaped.
7) Epigyne with distinct cavity, usually surrounded by sclerotized swellings.
8) Copulatory ducts mostly wide, helical.
Species included:
Racata brevis
sp. nov.
,
R
.
sumatera
sp. nov.
(
Indonesia
:
Sumatra
),
R
.
grata
Millidge, 1995
(
Indonesia
: Krakatoa,
Java
and Belitung) and
R. laxa
sp. nov.
(
Indonesia
:
Sumatra
;
Thailand
: Ko Chang).
Taxonomic remarks:
The genus
Racata
was established from a male and placed into the subfamily
Dubiaraneinae (
Millidge, 1995
)
on the basis of the structure of its embolic division. Due to the same reason
Millidge (1995)
also placed the following Southeast Asian genera into the
Dubiaraneinae
:
Kenocymbium
Millidge & Russell-Smith, 1992
,
Ketambea
Millidge & Russell-Smith, 1992
,
Prosoponoides
Millidge & Russell-Smith, 1992
and
Thainetes
Millidge, 1995
. The subfamily
Dubiaraneinae
is defined by only a single character of the vulva, i.e.: “… the seminal [= copulatory] duct of the epigynum running along the margins of a lamina, as in the
Mynogleninae
; in the majority of the species, the lamina is coiled into a short, almost planar helix, the axis of which is more or less perpendicular to the plane of the epigynum…” (
Millidge, 1993
). However, as pointed out by
Millidge & Russell-Smith (1992)
, the epigyne in all above mentioned genera (including
Racata
) is of the linyphiine
type
and is quite different from that of
Dubiaranea
Mello-Leitão, 1943
, the
type
genus of the
Dubiaraneinae
. At present it is premature to discuss the position of these genera in the system of subfamilies in the
Linyphiidae
until the subfamily
Dubiaraneinae
is clearly diagnosed. In the meantime I provisionally consider the genus
Racata
as belonging to the
Erigoninae
. The small size and erigoninelike general appearance, and the structure of the genitalia, which are similar to that of some Southeast Asian erigonines, i.e.,
Asiagone
Tanasevitch, 2014a
,
Houshenzinus
Tanasevitch, 2006
,
Laogone
Tanasevitch, 2014a
,
Nasoona
Locket, 1982
,
Oedothorax
Bertkau in
Förster & Bertkau, 1883
, etc., support the preliminarily inclusion of
Racata
in the
Erigoninae
. The only problem I see here is in the chaetotaxy formula, which is absolutely not characteristic for the subfamily, but rather for the
Micronetinae
or
Linyphiinae
.
The genus is closely related to
Aperturina
Tanasevitch, 2014b
, known from
Thailand
and West
Malaysia
(
Tanasevitch, 2014b
).
Distribution:
So far known only from
Indonesia
and
Thailand
.