Isognathotermes modicus Josens & Deligne, 2025

Josens, Guy, Deligne, Jean, Harry, Myriam, Roy, Virginie, Akama, Pierre D., Coulibaly, Tenon, Dosso, Kanvaly, Goergen, Georg, Hasson, Michel, Kasangij, Patrick Kasangij A, Kifukieto, Carmel, Ru, Bruno Le, Loko, Laura Estelle Yêyinou, Ndiaye, Abdoulaye Baila, Roisin, Yves, Sion, Noémie, Šobotnik, Jan, Stiblik, Petr, Kuenda, Soki Kue Di, Traoré, Saran, Viage, Manuela, Wango, Solange Patricia, Kaymak, Esra, Bourguignon, Thomas & Hellemans, Simon, 2025, An integrative revision of the genus Isognathotermes (Termitidae: Cubitermitinae) with description of seven new species and four new subspecies, European Journal of Taxonomy 1024, pp. 1-197 : 95-99

Isognathotermes modicus Josens & Deligne sp. nov.

urn:lsid:zoobank.org:act:

Figs 26–31, 50, distribution map: Fig. 53; Table 9

Diagnosis

This is a very small species (the smallest with a finitimus EVA ), so small that the first sample was initially thought to come from an incipient colony, but a physogastric queen ruled out this possibility.

The worker has a finitimus EVA and is among the smallest in the genus Isognathotermes : (WT3L = 1.12–1.20 mm), and its enteric valve is also the smallest ( Fig. 31).

The soldier is among the smallest in the genus Isognathotermes (SHdL = 2.42–2.66 mm), as small as the smallest I. fungifaber but with a finitimus EVA. It has evenly curved mandibles with a very low acceleration index of the mandible curvature between proximal and distal parts (ln(SMlpR) - ln(SMldR) = 0.96–1.44) as it is the case for some I. planifrons but with different sizes.

The imago, however, is among the medium-sized imagines in the genus Isognathotermes ( Fig. 26) and rather like those of I. finitimus , I. rectimalatus sp. nov., and I. planifrons .

To date, this species is only known from the “forêt des Abeilles”, Gabon.

Etymology

The epithet modicus means ‘modest’ in Latin. It refers to the small size of this species.

Material examined

Five samples from one location.

Holotype

GABON • soldier; Forêt des Abeilles ; 0°19′ S, 12°7′ E; 1995; C. Bordereau and A. Robert leg.; study code: DJ 0862; MNHN EP9886 .

Paratypes

GABON • worker, ♂ (king), ♀ (queen); same data as for holotype; MNHN EP9886 .

Other material examined

GABON • soldier, ♀ (queen); Forêt des Abeilles ; 0°19′ S, 12°7′ E; 1995; C. Bordereau (?) leg.; study code: DJ P214; MNHN EP9887 • soldier; Forêt des Abeilles ; 0°19′ S, 12°7′ E; 1995; C. Bordereau (?) leg.; study code: DJ P216; MNHN EP9888 • soldier, worker; Forêt des Abeilles ; 0°35′ S, 12°25′ E; 1995; C. Bordereau and A. Robert leg.; study code: DJ 0858; MNHN EP9884 • soldier, worker, ♂ (king), ♀ (queen); Forêt des Abeilles ; 0°35′ S, 12°25′ E; 1995; C. Bordereau and A. Robert leg.; study code: DJ 0859; MNHN EP9885 .

Historical review

This species is described here. It was discovered by C. Bordereau and A. Robert in the so-called “forêt des Abeilles”, Gabon.

Description

Imago

COLOUR. Head capsule: well sclerotised and dark C6–C7; fontanelle concolorous with head. Postclypeus one level paler than head capsule. Antennae C5–C6. Thorax: pronotum concolorous or almost so with head capsule; meso- and metanotum C6 slightly paler than head. Legs C4. Abdomen: tergites C6. Sternites appreciably paler in the middle (C3–C5) with both sides darker (C5–C6) than anterior.

SETATION. Head capsule, with some prominent setae set amongst a high density of short, fine setae forming a dense mat. Labrum and postclypeus with some prominent setae mixed with shorter ones. Antennae with some prominent setae, some more numerous smaller setae and, mainly distally on most articles, a bunch of very fine, bent setae (visible only at high magnification, 50 × or more). Thorax: pronotum with prominent setae mainly on margins and shorter ones in middle; meso- and metanotum with some fine, pale setae, arranged in a medio-longitudinal strip, generally visible at 20–40×; sometimes with one or two large setae on posterior lobe. Legs very pilose, furnished (among numerous fine setae) with 7–11 stronger setae on the carina of fore coxa and 1–3 on the ventral side of fore coxa and trochanter; tibia pilose, fore, mid, and hind tibia furnished with 30–40 spines and bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively. Abdomen: tergites with many large and small setae. Sternites with long setae, erect or directed slightly forward, and many long and smaller setae directed backwards.

STRUCTURE (measurements in Table 9, Fig. 50). Size: the imagines of I. modicus sp. nov. are, on average, medium sized in the genus Isognathotermes ( Fig. 26). Head capsule: compound eyes nearly round; ocelli shortly oval, removed from eyes by a distance equal to 0.9–1.3 ocellus small diameter; fontanelle generally a tiny round or elongate marking. Antennae: shortened to 12 articles by amputation of probably four articles in queens and kings. Labrum: cupola shaped, wider than long. Left mandible with apical tooth medium sized in the genus ( Fig. 27) and always more prominent than first marginal; marginal teeth three in number but second one only suggested by an undulation of edge between first and third marginal teeth; only the apical tooth is acute in unworn specimens; premolar tooth almost totally obscured by molar prominence in dorsal view; molar tooth bearing a rounded molar prominence dorsally and ending posteriorly in a tiny acute apophysis. Right mandible with apical tooth always more prominent than first marginal; marginal teeth two in number; first marginal tooth well developed with a sharp tip when fresh; second marginal tooth smaller and with a blunt tip even when fresh; molar tooth bearing a ventral rounded flange and ending posteriorly in a kind of heel. Thorax: pronotum appreciably wider than long and narrower than head width (including the eyes), straight to very weakly sellate with anterior lobe short and very slightly elevated. Fore coxa flanged ventrally resulting in a sharp carina. Gut not studied.

Soldier

COLOUR. Head capsule uniformly C5. Antennae and labrum one to two palette levels paler than head capsule. Mandibles dark (C6) with an abrupt clearing on their bases (one levels) which is generally the same colour as frons. Thorax and legs paler than head capsule (C4). Abdomen grey to red-brown owing to digestive bolus.

SETATION. Head capsule with few scattered setae; on frons a dense bunch of setae surrounds and overhangs fontanelle. Antennae with some prominent setae, more numerous smaller setae and at distal extremity of distal articles, a bunch of very fine, bent setae (visible only at high magnification, 50 × or more). Labrum with 4–6 large setae on each lobe. Thorax: pro- and mesonotum with a small number of setae mainly located on margins. Legs: fore coxa with at least one fine seta and 2–3 spines on carina and not any spine on ventral side; trochanter generally with some strong lined-up setae, including 3–4 spines; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively (the latter sometimes weakly developed) and a row of 6–12 spines along their shaft. Abdomen: tergites with some large setae, mainly or only on their posterior margins. Sternites with long setae, erect or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 9, Fig. 50). Size: the soldiers of I. modicus sp. nov. are part of the smallest soldiers in the genus Isognathotermes ( Fig. 28). Head capsule: always clearly sclerotised; appreciably longer than wide. Dorsal view: lateral sides mostly subparallel with a very slight narrowing near posterior third or fourth; from antennal sockets sides converge towards bases of mandibles; posterior side regularly convex. Slightly concave or straight upper profile; angle between extended mandibles and frons obtuse; frons flat or with a small anterior hump. Gulamentum in ventral view always constricted in its posterior half, with sides of anterior part roundly convex. Antennae: of 14.5–15 articles. Labrum: always deeply bifurcate and wider than long, with lyre-shaped sides; lobes angular, with fine, whitish, or translucent tips; anterior margin concave. Mandibles: sabre-like; inner edges smooth with one distinct but small marginal tooth, near molar tooth on each mandible; mandibles clearly shorter than head; entire surface of both mandibles smooth and glossy. Right mandible slightly more curved than left. Thorax: pronotum sellate, as wide as 56–60% of head width, with straight anterior and posterior margins. Fore coxa flanged ventrally resulting in a sharp carina. Gut: enteric valve seating on left side, best seen in ventral view, situated in second half of abdomen. Caecum rather small, best seen in ventral view, near centre of abdomen, three-lobed. Arrangement of enteric valve cushions showing trilateral symmetry, the odd cushions recognizable as a finitimus EVA.

Worker

COLOUR. Head capsule pale (C2–C3). Antennae: proximal articles pale (C2), distal articles two levels darker (C4). Thorax, nota, and legs pale (C2–C3). Abdomen grey to red-brown owing to digestive bolus.

SETATION. Head capsule and postclypeus with few, erect, scattered setae. Labrum with few, robust scattered setae. Antennae with some prominent setae, some more numerous smaller setae and at distal extremity of distal articles, a bunch of fine, bent setae (visible only at high magnification, 50 × or more). Thorax: nota with some scattered setae. Legs: fore coxa carinated, bearing one fine seta and furnished with 3–5 spines on carina and not any one on ventral side; fore trochanter with 4–6 lined up spines; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of 6–12 spines. Abdomen: tergites with scattered setae. Sternites with long setae, erect or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 9, Fig. 50). Size: the workers of I. modicus sp. nov. are the smallest workers with a finitimus EVA , of the same size as the smallest workers of I. fungifaber (which have a fungifaber EVA ). Head capsule: weakly sclerotised (except mandibles). Antennae: 14.5 articles. Labrum: cupola shaped. Left mandible: apical tooth well developed with a sharp tip when fresh; marginal teeth three in number, first marginal well developed but with a blunt tip even when fresh, second marginal faint (visible as an undulated edge and disappearing in worn mandibles), third marginal with a blunt tip; premolar tooth with its proximal end generally hidden under molar prominence; molar tooth bearing a rounded molar prominence dorsally and ending posteriorly in a tiny acute apophysis. Right mandible: apical tooth well developed with a sharp tip when fresh; marginal teeth two in number; first marginal well developed with a sharp tip when fresh; second marginal smaller and with a blunt tip even when fresh; molar tooth bearing a ventral rounded flange and ending posteriorly in a kind of heel. Thorax: pronotum sellate, as wide as about 64% of head width. Fore coxa flanged ventrally resulting in a sharp carina. Gut: enteric valve seating on left side, best seen in ventral view, situated in posterior half of abdomen. Arrangement of enteric valve cushions of the finitimus pattern with triradial symmetry: the odd PCs, in their downstream part, are wide and bear at that place a high density of rather short bristles on a globular bulge ( Fig. 50); supporting bristles are rather numerous: 20–28 on each side of the odd PCs; secondary cushions are wide at the upstream end, narrowing noticeably downstream with a homogeneous spine scattering. Caecum always rather small, visible in ventral view, near centre of abdomen, shortly lobed (three or four small lobes).

Chorology-ecology

To date, this species is only known only from the “Forêt des Abeilles”, Gabon, at the limit of the northwestern Congolian lowland forests and the Atlantic equatorial coastal forest ecoregions ( Fig. 53).

Molecular data

No genetic sequence is currently available.