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A new genus and species of subterranean diving beetle from Laos
(Coleoptera, Dytiscidae, Hydroporinae, Hydroporini)
Pierre Queney1, Jean-Michel Lemaire2 & Marina Ferrand3
1 10 rue Descartes, F – 92190 Meudon, France <pierre.queney@wanadoo.fr>
2 Attaché scientique au Muséum d’Histoire naturelle de Nice, 2162 chemin du Destey, F – 06390 Contes, France
<troglorites@mac.com>
3 27 avenue Louis Pasteur, F – 92220 Bagneux, France <marina.ferrand@inra.fr>
http://zoobank.org/3060D42E-8223-4D72-8B8C-3C4793DD7E15
(Accepté le 28.X.2020 ; publié le 10.XII.2020)
Abstract. – The rst stygobiontic diving beetle known from Laos, Laodytes lapiei n. gen., n. sp., is described from a
cave located in the Vientiane province. Its morphological characters lead to its placement, among Hydroporinae,
in Hydroporini. Inside these, the new species could not be assigned to an existing genus. As a result, a new genus
has been dened without it being possible, at the present stage, to assign it to one of the currently recognized subtribes.
Résumé. – Nouveaux genre et espèce de Coléoptère aquatique souterrain du Laos (Coleoptera, Dytiscidae,
Hydroporinae, Hydroporini). Le premier Dytiscidae stygobie connu du Laos, Laodytes lapiei n. gen., n. sp., est
décrit d’une grotte de la province de Vientiane. Ses caractères morphologiques conduisent à le placer, parmi les
Hydroporinae, dans les Hydroporini. À l’intérieur de ceux-ci, la nouvelle espèce n’a pu trouver place dans aucun
genre existant. En conséquence, un nouveau genre a été déni, sans qu’il soit possible, à ce stade, de le rattacher
à l’une des sous-tribus actuellement reconnues.
Keywords. – Stygobiontic, speleology, oriental region, aquatic beetle.
_________________
During a speleological expedition to Laos, which took place in March 2019, the third author
(MF) collected three specimens of a small diving beetle in a cave of the Pha Lay mountain
range, near Kasi. Since this was the dry season, she was able to progress in this cave along several
fossil levels (g. 1) for more than 2 km under the range. At the intersection with a muddy sys-
tem of galleries, she reached a more humid lower oor, climbing down a block chaos followed
by a calcite ow; there, water from the last oods remained in residual pools and even ew
along a small channel. The calcite ow was darkened by guano deposits: although no bats
were seen during the visit, they should rest at times in the overhanging fault crack on in the
ceiling. The beetles were found swimming in one of the pools (g. 2). More recently, during
an expedition in March 2020 to the same cave, eight more specimens were found in the lower
fossil level (g. 17). There also, a little water was owing along calcite cascades, coming from
the upper level where a lake stands.
Subterranean genera of beetles are rather numerous in Dytiscidae, and the recent book
of miLLer & Bergsten (2016) has cleared up their classication. However, convergences in
morpho logy due to stygobiontic life are so prominent that determination keys cannot avoid
calling upon geographic distribution. Most of the discovered Dytiscidae belong to Hydroporinae
and the Laotian species is no exception. Nonetheless, a few Copelatinae are also stygobiontic,
in particular Exocelina sugayai Balke & Ribera, 2020, recently described from the Malay
Peninsula (BaLke & riBera, 2020). In the Oriental region, a few Bidessini and Hyphydrini
are known, and also the genus Siamoporus Spangler, 1996, placed among Hydroporini by its
Bulletin de la Société entomologique de France, 125 (4), 2020 : 407-416. ISSN 0037-928X
https://doi.org/10.32475/bsef_2144 eISSN 2540-2641
408
author, but considered as incertae sedis in this tribe, and possibly in Hydroporinae as a whole
(miLLer & Bergsten, 2016 : 152).
The morphological features of our specimens have been compared with those of all
known genera of Dytiscidae. A detailed analysis is given below. It appears that they do not
properly t in any known genus. Therefore, a new taxon is described below as Laodytes lapiei
n. gen., n. sp.
Material and Methods
The rst three specimens were collected by hand and immediately put in an Eppendorf
vial containing 70° ethanol. Back in France, MF sent the beetles to the second author (JML)
for study, together with pictures she had taken of them in the preserving uid. One picture
(g. 3) shows the long sensory hairs surrounding the body, which unfortunately did not with-
stood the dry mounting.
With miLLer & Bergsten (2016) at hand, JML recognized that those diving beetles, two
males and one female, did not appear to t any species mentioned in this book; he therefore
asked the rst author (PQ) to lend a helping hand. PQ succeeded in extracting the genitalia of
one male. Given its tiny size (0.2 mm), we decided to mount it on a glass slide in DMHF resin;
we thus could obtain a clear view of the organ (g. 14), at the cost of some attening by the
coverslip. Later, with eight more specimens available, JML mounted another male genitalia
in a drop of mounting media DMHF without coverslip, to obtain more natural views of the
organ (g. 15-16). These pictures were taken with an Olympus™ TG4 camera, adapted to an
Olympus CX21 optical microscope through a LM-Scope™ adapter. High-resolution pictures
of the external morphology (g. 4-12) have been kindly taken by Michel Perreau on a Keyence™
VHX5000 microscope equipped with a VH-Z250T camera lens. The lateral view (g. 13) was
obtained with a Toupcam™ 14 Mp CMOS camera mounted on an Olympus™ SZX9 stereo-
microscope, from several shots assembled with HeliconFocus™ v.7.6.
Fig. 1. – View of the Tham Pha cave.
Queney et al. – Un nouveau Dytiscidae souterrain du Laos
409
taxonoMy
Laodytes n. gen.
http://zoobank.org/374332F7-4F3C-444E-AEE4-B49AD388A795
Type species: Laodytes lapiei n. sp.
Diagnosis. – The new genus is distinguished by the following combination of characters:
Body very small (< 1.5 mm), broad, parallel-sided; dorsal and ventral surfaces mainly reticulate
and matt. Head wide, encased between strongly protruding pronotal angles. Second anten-
nomere conspicuously wider than the rst, the middle ones ovoid, the last one elongated and
tapered. Pronotum transverse, without a lateral longitudinal stria on each side, its lateral edges
in continuity with those of fused elytra. Prosternal process lanceolate, with apex not reaching
metaventral process. Metacoxal lines absent; interlaminary bridge of metacoxae broadly exposed;
hind margin obtusely emarginate medially, lateral lobes incised and not rounded. Ventrites
(visible sternites) 2 and 3 fused. Fore and mid legs rather thick, hind legs slender. Sucker cups
on male pro- and mesotarsus absent. Median lobe of aedeagus gutter-like, nearly symmetrical
in sagittal view, and almost straight beyond the basal bend in lateral view; apex rounded; para-
meres symmetrical, single segmented, slightly longer that the median lobe, each lobe in the
shape of an elongated triangle, narrowly tapered with a single bristle at tip.
Etymology. – A combination of Lao, the name of the people and language of Laos, and dytes (δύτης),
diver in Greek.
Laodytes lapiei n. sp.
http://zoobank.org/069B1979-6A73-4F79-81D6-953C20F7B14D
Holotype: ♂, grotte Tham Pha, Ban Phato, Laos, alt. 460 m, 19.III.2020, Marina Ferrand
leg., deposited in Muséum national d’Histoire naturelle, Paris.
ParatyPes: 4 ♂, 3 ♀, same data; 2 ♂, 1 ♀, same locality, 18.III.2019, Marina Ferrand leg., in coll.
P. Queney and J.-M. Lemaire.
Type locality. – Laos, district of Kasi, province of Vientiane: cave Tham Pha, near Ban
Phato, 17 km SW to Kasi, 19.13204°N 102.12079°E, altitude 460 m.
Description of male. – Habitus (g. 4-5): body length 1.35 mm, maximum width 0.62 mm; species
blind and depigmented, uniformly pale orange; body stocky, parallel-sided, weakly convex in lateral
view; in dorsal view, lateral outline showing an almost perfect continuity between pronotum and elytra.
Head (g. 6-7) wide, front margin semicircular, very deeply inserted in pronotum. Eyes totally
absent; clypeal suture reduced to a short depression on the sides. Surface glabrous, with an isodiametral
reticulation, forming a rather regular hexagonal lattice, strong on frons but vanishing on clypeus and
sides. Antennae with a cylindrical scape and a thicker and swollen pedicel (g. 6-7), middle segments
globular (g. 4-5), segments 6-10 slightly thicker than 3-5, apical segment elongate and conical in the
distal half; clypeus slightly and shortly rimmed above antennae. Maxillary palpi four-segmented, with
the last segment 2.5 times longer than wide, ovoid basally and acuminated at tip. Ligula triangular and
acute, labial palpi three-segmented, the last segment twice longer than wide (g. 7).
Pronotum (g. 6) not cordiform but widely rectangular, almost parallel-sided seen from above, but
strongly sinuated in lateral view: edge strongly concave bottomwards, in the basal third, then slightly
concave upwards to the front angles; almost as wide as elytra and strongly wider than the head, with
protruding front angles encasing the head to the basal third; front margin straight along the posterior part
of head; base V-shaped in the middle, sinuated towards right posterior angles; sides with a rimmed gutter,
the anterior two-thirds of which contain 6-7 setigerous punctures, provided with deciduous sensory bristles; in
lateral view (g. 13), the side edge sinuated and not in continuity with the elytral edge. Surface strongly
reticulated as on hind part of head, the meshes polygonal but a little wider, reticulation vanishing on
sides; the posterior margin showing a short and faint notch near the external third, followed externally by
Bulletin de la Société entomologique de France, 125 (4), 2020 : 407-416
410
Fig 2-5. – Laodytes lapiei n. gen., n. sp. – 2, Specimen alive, in situ. – 3, Specimen in preserving uid. – 4-5, Habitus,
male: 4, dorsal view; 5, ventral view.
Queney et al. – Un nouveau Dytiscidae souterrain du Laos
411
Fig. 6-12. – Laodytes lapiei n. gen., n. sp., ♂. – 6, Head and pronotum, dorsal view. – 7, Head, ventral view. – 8, Pro-
sternal process. – 9, Metaventrite and metacoxae. – 10, Metacoxal process. – 11, Protarsus. – 12, Metatarsus.
Bulletin de la Société entomologique de France, 125 (4), 2020 : 407-416
412
shorter and weaker creases; small punctures distributed
along an irregular row along the front margin, other
smaller punctures scattered on the disk. Pronotum
and elytra seem welded together.
Elytra (g. 4) 1.45 times as long as wide
together and fused, sides almost parallel on basal
third, then regularly narrowing into a semi-circular
apex when seen from above; basal surface reticu-
lated, with larger meshes than on the pronotum;
on the disk, those meshes turning into small round
cavities, getting longer than wide and then fading
apically; a vestigial sutural stria visible on the distal half; about 25 pores, provided with long sensory bristles,
distributed along the lateral edges. Hind wings absent.
Ventral surface (g. 5) uniformly pale, like the dorsal surface, and largely reticulate; prosternal
process (g. 8) lanceolate with acuminate apex not reaching anteromedial metaventral process (g. 9);
epipleuron getting regularly narrower to the metacoxae level, without oblique carina near shoulder; metepi-
sternum in right triangle, about twice longer than wide; metaventral wings very narrow; metacoxal lines
absent (g. 9): only a attened raised plate visible on each side of the median groove; metacoxal process
(g. 10) with median part extended backwards; hind margin obtusely emarginate medially, with each side
obliquely cut and both margins converging forward; lateral lobes not rounded, deeply incised and at;
disk of metacoxae reticulated; metacoxal process with median part extended backwards slightly above
the abdomen; the latter with ve visible ventrites, the second and third, usually distinct in Dytiscidae, being
fused; reticulation isodiametral on the anterior part of this second ventrite, transverse on its posterior part
and on the next two ventrites, isodiametral on the last.
Legs. Pro- and mesotarsi four-segmented, rather wide, pro- and mesotibiae short and dilated on
the distal half (g. 5), pro- and mesotarsomeres 1-2 with adhesive setae but without distinct sucker
cups (g. 11), hind legs thinner with oblong femora and large oval hind trochanters (g. 10); mesotibiae
densely adorned with spiny setae; metatrochanters reticulated with transversely elongated meshes; meta-
tarsal claws of subequal length (g. 12).
Aedeagus (Figs. 14–16): as described in the genus diagnosis.
Fig. 13. – Laodytes lapiei n. gen., n. sp., habitus, right
lateral view.
Fig. 14-16. – Laodytes lapiei n. gen., n. sp., aedeagus. – 14, Ventral view (slide with coverslip). – 15, Oblique view
(with genital segment). – 16, Lateral view.
Queney et al. – Un nouveau Dytiscidae souterrain du Laos
413
Female. – External sexual dimorphism limited to the protarsi, thinner than those of the male and
without visible adhesive setae.
Etymology. – We dedicate the new species to Guillaume Lapie, biospeleologist and team partner of
the discoverer. The specic epithet is a substantive in the genitive case.
Habitat. – Stygobiontic, found swimming in calcite pools.
Distribution. – So far, only known from the type locality in Laos.
discussion
Following miLLer & Bergsten (2016) and the presentation given by Fery & riBera (2018),
the new taxon clearly belongs to Hydroporinae, in view of the following characteristic features:
– scutellum invisible;
– anteromedial part of prosternum not on the same plane as its process;
– pro- and mesotarsi with four visible segments;
– metatarsomeres with distal margins not lobed.
Fig. 17. – Topography of the Tham Pha cave (© EEGC 2020).
Bulletin de la Société entomologique de France, 125 (4), 2020 : 407-416
414
Table I. – Comparison of Sinodytes hubbardi Spangler, 1996, and Laodytes lapiei n. gen., n. sp. Main differences
noted from sPangLer (1996) and present description.
Laodytes lapiei Sinodytes hubbardi
Measurements
– total length 1.35 mm 1.68 mm
– maximum width 0.62 mm 0.72 mm
– total length/ maximum width 2.17 2.33
Outline of the body angle between pronotum and
elytron sides inconspicuous
angle between pronotum and
elytron sides very notable
Dorsal surface
– head
width/ height: 2.02
head height/pronotum height: 0.86
discal area reticulate
width/ height: 1.57
head height/pronotum height: 1.15
discal area punctured
– pronotum
sides parallel;
protruding front angles encasing
higher and straighter the head;
base V-shaped in the middle but
very rounded
strongly reticulate with small
punctures scattered on the disk
sides converging towards the base;
protruding front angles little
encasing the head;
base V-shaped and angular in the
middle
disk reticulate and coarsely
punctured
– elytra
sides not parallel and narrowing
downwards fairly regularly
basal surface reticulate, on the
disk meshes turning into small
round cavities
sides parallel then strongly
rounded downwards
coarsely punctured
Antennae
antennomere II very big and
nearly twice longer than III;
antennomeres II-X short and
ovoid-shaped
antennomere II only 1.33 longer
than III; antennomeres II- X
long and not ovoid-shaped
Maxillary palps last segment elongated last segment dilated
Ventral surface
– labium gula and gena narrow in height gula and gena wide in height
– prosternal process
lanceolate with acuminate apex
behind mesocoxae
ending in an acute apex but
widening in a curve behind
mesocoxae
– metacoxal plates a attened raised area visible on
each side of the median groove
no raised area visible in the middle
– metepisternum very wide narrow
– metaventral wing very narrow narrow
– metaventrite
suture between metaventrite and
metacoxae broadly rounded
medially
suture between metaventrite and
metacoxae angular medially
– last ventrite regularly rounded pointed in shape
Legs
– metatrochanter ovoid-shaped slightly pointed in shape
Queney et al. – Un nouveau Dytiscidae souterrain du Laos
415
Within Hydroporinae, the following combination of characters rules out all other tribes
than Hydroporini:
– pronotum and elytra without a pair of basal striae (or plicae);
– metepisternum reaching mesocoxal cavities;
– metafemur along the dorsal margin broadly separated from the metacoxal lobe by meta-
trochanter;
– metatarsal claws subequal in length;
– medial portion of metacoxae in a different plane from the base of abdomen;
– parameres of aedeagus single-segmented.
Assigning the new taxon to one of the presently admitted subtribes of Hydroporini,
Hydro porina, Siettitiina and Deronectina, is not obvious. After taking into account the key of
miLLer & Bergsten (2016) and the arguments of Fery & riBera (2018), we were unable to
conclude to which subtribe the new genus should be attached. We encountered difculties that
other subterranean genera have already met in the past. The closest case to the new genus is
probably that of Siamoporus Spangler, 1996, from Thailand, currently considered as incertae
sedis (miLLer & Bergsten, 2016 : 152) among Hydroporinae.
Indeed, Siamoporus shows some similarities with the new species: male pro- and meso-
tarsi four-segmented, pro- and mesotarsomeres 1-2 with adhesive setae but without distinct
sucker cups, metacoxal process medially emarginate and strongly incised posterolaterally for
reception of metatrochanter, the latter large, elongate and inated, ventrites (visible sternites)
2 and 3 fused; on the other hand, the Laotian insect differs from Siamoporus in many ways:
pronotum not cordiform but rectangular, elytra fused, metacoxal lines absent, aedeagus very
different.
Another case of incertae sedis genus is Sinodytes Spangler, 1996. It was described on a
single female, which seems to be lost (miLLer & Bergsten, 2016 : 253), and was provisionally
assigned to Bidessini by its author. The Laotian species cannot belong to this tribe because of
its non-segmented parameres, but one must acknowledge that it bears a strong similarity of
habitus with Sinodytes hubbardi Spangler, 1996, at least on the basis of the only known repre-
sentation of this species (sPangLer, 1996: g. 39-40).
If Spangler’s drawing is accurate, the outline of the body, and proportions of the head and
prothorax are so different that the Laotian species cannot be the same as Sinodytes hubbardi. We
detail in table I the main differences we noted in the comparison of the two species. Nevertheless,
although many features in Spangler’s description seem to differ from ours, the assignment
of our species to Sinodytes remains plausible and supported by biogeography. However, this
would imply redening the genus Sinodytes and in particular moving it away from Bidessini.
In the absence of a male specimen and even of the holotype, we feel more appropriate to create
the new genus Laodytes on the Laotian specimens, keeping in mind that the discovery of a
male from Jiazhai Taiping cave may lead to synonymizing Laodytes with Sinodytes, or not !
acknowLedgements. – The authors congratulate the caving association EEGC (Études et Explorations des
Gouffres et des Carrières) for having organized the so-called Phouhin Namno expeditions in the Kasi area since 2010,
which led to the discovery of several cave-dwelling animals new to Science. Pictures inside the Tham Pha cave were
taken by François Lallier. We warmly thank our colleague and friend Michel Perreau for the high denition focus
stacked pictures of a male paratype.
references
BaLke m. & riBera i., 2020. – A subterranean species of Exocelina diving beetle from the Malay Peninsula
lling a 4,000 km distribution gap between Melanesia and southern China. Subterranean Biology,
34 : 25-37. https://doi.org/10.3897/subtbiol.34.50148
Bulletin de la Société entomologique de France, 125 (4), 2020 : 407-416
416
Fery H. & riBera i., 2018. – Phylogeny and taxonomic revision of Deronectina Galewski, 1994 (Coleo-
ptera: Dytiscidae: Hydroporinae: Hydroporini). Zootaxa, 4474 (1) : 1-104.
https://doi.org/10.11646/zootaxa.4474.1.1
miLLer k. B. & Bergsten J., 2016. – Diving Beetles of the World: Systematics and Biology of the Dytiscidae.
Baltimore : Johns Hopkins University Press, 320 p.
sPangLer P. J., 1996. – Four new stygobiontic beetles (Coleoptera: Dytiscidae; Noteridae; Elmidae).
Insecta Mundi, 10 : 241-259.
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Queney et al. – Un nouveau Dytiscidae souterrain du Laos
