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Description of previously overlooked specimens of
Nemesia rastellata (Araneae, Mygalomorphae:
Nemesiidae) from the type locality, with notes on
functional aspects of male morphology
Author: Decae, Arthur
Source: Arachnologische Mitteilungen: Arachnology Letters, 65(1) : 5-7
Published By: Arachnologische Gesellschaft e.V.
URL: https://doi.org/10.30963/aramit6502
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Arachnologische Mitteilungen / Arachnology Letters 65: 5-7 Karlsruhe, August 2023
Wunderlich (2011) described Nemesia rastellata from a male
specimen in the collection of the Senckenberg Museum in
Frankfurt am Main. e specimen was collected by R. Kin-
zelbach in September 1963 on the Greek island of Karpa-
thos. Wunderlich (2011) noted that the type specimen was
in rather poor condition by stating that “the opisthosoma of
the spider and the right pedipalpus have been separated, the
opisthosoma is deformed” (sic). e female of the species was,
and still is, unknown. At the time of Wunderlich’s descrip-
tion, part of the mygalomorph spider collection was loaned
out to the author of the present article and thus absent from
the Senckenberg Museum collection. A request from the
Senckenberg curator to return the loan in May 2022 triggered
renewed attention for the contents of this loan collection and
the discovery of three vials (four specimens) that were appar-
ently incorrectly labelled as containing specimens identied
as members of the family Atypidae. In fact, these vials ap-
peared to contain four males of N. rastellata (fam. Nemesi-
idae). Moreover, the vial-labels indicated that these specimens,
like Wunderlich’s holotype, were collected on Karpathos by
R. Kinzelbach. As these four specimens were absent from the
Senckenberg collection at the time of Wunderlich’s descrip-
tion of N. rastellata (2011), they are likely to have been col-
lected together with the type specimen.
e four retrieved male specimens are here described, pro-
viding additional information for taxonomic recognition of
the species and a rst insight into intraspecic morphological
variation in N. rastellata.
Material and methods
e sample consisted of four specimens in three separate vials.
Two vials contained single specimens, the third vial contained
two specimens (see paragraph ‘Studied material’ below). All
specimens were studied with the aid of a Huvitz HSZ-645TR
stereomicroscope equipped with a Lusis HC-20CU camera
operating on Panasis software and an Euromex iScoop com-
pact microscope equipped with a Euromex VC-3031camera.
Both systems allow multiple focus photography and precision
measurement. Figures were prepared with Adobe Photoshop
elements 2022 and Helicon Focus 7. Terminology used and
measuring methods follow Cassar et al. (2022). Measure-
ments are given in millimetres. Size measurements (see be-
low) are given as minimal–maximal values found across the
sample of four specimens. Ratios (see below) provide an im-
pression of the shape and relative size of dierent body parts.
Ratios are also given as minimal–maximal ranges.
Terminology. e following terminology pertaining to male
Nemesia morphology is used: 1) Clasper-hook (CH), this is
the single strong, rigid, curved and sharp-pointed “hook” or
“spur” placed on a prominent apophysis in a ventro-distal,
prolateral position of tibia I (Fig. 2d-e). 2) Palp-tibia rake
(PTR), this is a transverse row of particularly strong, distally
directed spines along the dorso-distal margin of the palp-
tibia. In some Nemesia species, or species groups, the one or
more similar strong spines are present just proximal of the
apical row (Fig. 2f). 3) Striae are ne, longitudinal ribs on
the embolus found in most Nemesia species that occur in the
eastern Mediterranean Region (Decae 2012).
Abbreviations. AME: anterior median eye(s), AR: width an-
terior eye-row; BuL: length bulb; CL: carapace length; CH:
clasper-hook; CW: carapace width; diaALE: diameter an-
terior lateral eyes; diaAME: diameter anterior median eyes;
diaPLE: diameter posterior lateral eyes; disAME: distance
between anterior median eyes; EL: length eye-group; EmL:
length embolus; Fem4: length femur IV; L1: length leg I;
L1TiL: length tibia I; L1TiW: width tibia I; L2: length leg
II; L3: length leg III; L4: length leg IV; LL: length labium,
LW: width labium; Met4: length metatarsus IV; PL: length
palp; PR: width posterior eye-row; PTR: apical rake on dorsal
palp tibia; PTiL: length palp tibia; PTiW: with palp tibia; sd:
standard deviation; SL: length sternum; SW: width sternum;
T1–T4: respective lengths of tibiae I, II, III, IV; TBL: total
body length; Tib4: length tibia IV.
Description of previously overlooked specimens of Nemesia rastellata
(Araneae, Mygalomorphae: Nemesiidae) from the type locality, with notes
on functional aspects of male morphology
Arthur Decae
doi: 10.30963/aramit6502
Abstract. Previously overlooked material of Nemesia rastellata Wunderlich, 2011, collected at the type locality and present in the col-
lection of the Senckenberg Museum in Frankfurt am Main, is here described. This description provides important new information for
taxonomical recognition of the species and the rst observations on intraspecic variations in size and shape in N. rastellata. Additionally,
aspects of male morphology in Nemesia trapdoor spiders are discussed from a functional perspective.
Keywords: Greece, intraspecic variation, Karpathos, rastellum, trapdoor spiders
Zusammenfassung. Beschreibung bisher übersehener Exemplare von Nemesia rastellata (Araneae, Mygalomorphae: Nemesi-
idae) von der Typuslokalität, mit Anmerkungen zu funktionalen Aspekten der männlichen Morphologie. Bisher übersehenes
Material von Nemesia rastellata Wunderlich, 2011, gesammelt an der Typuslokalität und Teil der Sammlung des Senckenberg Museums
in Frankfurt am Main, wird in dieser Arbeit beschrieben. Die Beschreibung enthält wichtige neue Information für die taxonomische Be-
stimmung der Art und die ersten Beobachtungen zu intraspezischen Variationen von Größe und Form innerhalb N. rastellata. Zusätzlich
werden Aspekte der männlichen Morphologie von Falltürspinnen der Gattung Nemesia aus funktionaler Perspektive diskutiert.
Arthur DECAE, Natural History Museum Rotterdam, Westzeedijk 345 (Museumpark),
3015 AA Rotterdam, The Netherlands; E-mail: arthurioDK@icloud.com,
ORCID: https://orcid.org/0000-0003-1427-4435
Academic editor: Petr Dolejš
submitted 18.11.2022, accepted 20.3.2023, online 4.8.2023
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6A. Decae
Fig. 1: Nemesia rastellata male, general somatic characters. a. SMF18e, general appearance; b. SMF11e, lateral carapace, note at cephalic part and pro-
minent ocular process (cf. Wunderlich 2011: g. 25); c. SMF21e1, dorsal prosoma, note anterior narrowing carapace and fovea with prominent central
groove (cg) (cf. Wunderlich’s (2011) median notch on g. 24); d. SMF11e, eye-group, note large anterior eyes and black pigmented ring around AME (br);
e. SMF18e, ventral chelicerae ventro-lateral view, note rastellum (ra) and smooth fang-ridge (sr); f. SMF11e prolateral tibia and patella III, note three spines
in line (ps) on the patella, other specimen have either two or three spines in this row; g. SMF11e, spinnerets, note knob-shape of PMS. Scale bars = a. 2.0
mm, b, c, f. 1.0 mm, d, e, g. 0.5 mm
Taxonomy
Nemesia rastellata Wunderlich, 2011 (Figs 1-2)
Studied material. Four male specimens labelled: 87-Atyp-
idae, deposited at the Senckenberg-Museum Frankfurt am
Main. Vial labels indicate that the specimens were collected
in Greece, on the island of Karpathos, by R. Kinzelbach and
bear the collection numbers 11e, 18e and 21e. For purpose
of study all specimens were placed in separate vials and rela-
belled as: SMF11e, SMF18e, SMF21e1 and SMF21e2.
Description. Within the genus Nemesia, body sizes of males
range from approximately 7.5 to 18.5 millimetres (informa-
tion from literature available in the World Spider Catalog
2023). With an average body length of 7.4 (sd. 1.14, n = 4)
N. rastellata is among the smallest species within the genus.
Wunderlich’s (2011) diagnosis and description are accurate.
Detailed observations on measurements and size ratios of
body-parts are given below. e following characters, of addi-
tional diagnostic value at the species level, not reported on in
Wunderlich (2011), are: (1) the black pigmented ring around
each AME (Fig. 1d). (2) Patella III has either two or three
prolateral spines (Fig. 1f). (3) Spinnerets, although not well
preserved in the sample, show spigots spread widely over the
ventral surface of the median and proximal segment of the
PLS and apically on the knob-shaped PMS (Fig. 1g). (4) e
embolus is ornamented with longitudinal, distally converging
curved ribs (Fig. 2a-b) relating N. rastellata to a large and di-
verse species-group within the genus Nemesia that has its cen-
tre of diversity in the eastern Mediterranean (Decae 2012).
(5) Contrary to Wunderlich’s (2011) observation (g. 27) the
apophysis of the CH is very short (Fig. 2d) in all specimens in
the sample. (6) In ventral view the CH is weakly sigmoid in
shape (Fig. 2e). (7) e PTR was found to be very constant in
shape and composition with three spines in a transverse api-
cal row and a fourth spine slightly more proximo-retrolateral
(Fig. 2f), this is slightly dierent from Wunderlich’s (2011)
observation (g. 29). (8) e fangs have a smooth ventral
ridge (Fig. 1e).
Size measurements (n = 4). Body parts: TBL 6.2–9.2; CL
2.7–4.0; CW 2.0–3.1; SL 1.6–2.1; SW 1.1–1.5; LL 0.3–0.4;
LW 0.4–0.6. Eye-group: AR 0.56–0.73; PR 0.54–0.71; EL
0.29–0.47; diaALE 0.17–0.23; diaPLE 0.12–0.19; diaAME
0.12–0.13; disAME 0,06–0.11. Palps and legs: PL 3.3–4.7;
L1 8.2–11.6; L2 7.5–10.8; L3 6.9–10.5; L4 10.6–15.6. Blub:
BuL 0.6–0.9; EmL 0.3–0.4.
Ratios (n = 4). CW/CL 0.63–0.78; EL/PR 0.52–0.56; SW/
SL 0.59–0.72; LW/LL 1.38–1.41; PTiW/PTiL 0.48–0.59;
L1TiW/L1TiL 0.40–0.45; Fem4/Met4 0.87–0.98; Tib4/
Met4 1.05–1.09.
Discussion
Wunderlich named the species after three prominent ‘rastella’
(rows or groups of particularly strong spines) that he found
to be present: 1) on the distal chelicerae, just above the base
of the fang (Fig. 1e), 2) on the dorso-distal palp-tibia (Fig.
2f ) and 3) on the cymbium (Fig. 2f ). It should be noted that
Wunderlich’s three ‘rastella’ are a general feature of Nemesia
males (at genus level), and therefore have no practical value
in the diagnostics of Nemesia species. Furthermore it is cus-
tomary that only the group of strong and ridged spines at
the apex of the basal segment of the chelicerae (Fig. 1e) is
referred to as the rastellum (e.g. Main 1967: 9, Ubick et al.
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Redescription of Nemesia rastellata 7
2005: 270, Jocqué & Dippenaar-Schoeman 2006: 24, Foelix
2011: 336). e cheliceral rastellum, that is functional in bur-
row construction, is a common feature in fossorial mygalo-
morph spiders of various genera and families. Personal obser-
vations indicate that the rastellum is not used for digging-up
soil, but rather for compressing soil in the burrow walls and
entrance region during burrow construction, and in shaping
(molding) the trapdoor. Compressing the soil in the burrow
wall and entrance results, probably in combination with a ce-
menting secretion from the mouth (personal observation), in
the formation of a sturdy plastered clay lining of the burrow
shaft (Nascimento et al. 2021). Burrow construction is exclu-
sively preformed by juvenile and female spiders, which leaves
the functionality of the male rastellum an open question. In
contrast to the cheliceral rastellum present in juveniles, fe-
males and males, rastella on the palp tibia and cymbium de-
scribed by Wunderlich are exclusively present in adult males.
ese structures, together with the CH and modied meta-
tarsus I (Fig. 2d-e) are apparently parts of the male defensive
equipment which is functional in sexual encounters (personal
observation).
e clasper-hook (Fig. 2d-e) is functional in locking
the female fangs during copulation. e terminology here
used is function-oriented and preferred over ‘megaspine’, the
purely structural description of this structure proposed by
Raven (1980). e CH is present in all Nemesia and Ibere-
sia males and is a main diagnostic character to distinguish
these two nemesiid genera from two other Mediterranean
nemesiid genera: Brachythele (forked CH) and Amblyocare-
num (CH absent).
e dark eye-ring around the AME (Fig. 1d), here propo-
sed as a possibly species level diagnostic character, might be
an artefact of preservation in which the cuticle of the carapace
has become slightly loose from the deeper lying prosoma.
Acknowledgements
I would like to thank Julia Altman and Peter Jäger of the Sencken-
berg Museum for the long-term loan of valuable specimens from the
mygalomorph spider collection. Petr Dolejš, Konrad Wiśniewski and
Tobias Bauer are thanked for their valuable suggestions and editorial
work on the initial version of the typescript.
References
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Fig. 2: Nemesia rastellata male, sex related characters.
a-b. Right-side copulatory organs of two dierent
specimens viewed under dierent rotation angles; a.
SMF11e, note longitudinal ribs (striae) on the embolus
(st); b. SMF18e, note the blunted embolus tip (bt) with
apical pore (cf. Wunderlich 2011: g. 31); c. SMF.21e1,
general palp morphology, note relatively simple pyri-
form bulbs with short, distally pointed emboli (cf. De-
cae 2012: g. 1); d. SMF11e, left distal leg I retrolateral
view, note short apophysis clasper-hook (sa) (contra
Wunderlich 2011: g. 27); e. clasper-hook (CH) in vent-
ral view, note weakly sigmoid shape (sh); f. distal palp
in dorsal view, note the four strong spines of the PTR
and spine-group on the cymbium (cs) (cf. Wunderlich
2011: g. 29). Scale bars = a, b. 0.2 mm, c, e, f. 0.5 mm,
d. 0.5 mm.
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