Isognathotermes congoensis ( Emerson, 1928 )

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 : 168-171

Isognathotermes congoensis ( Emerson, 1928)

Figs 22, 28, 30–31, 36–37, distribution map: Fig. 38; Table 19

Mirotermes ( Cubitermes) congoensis Emerson, 1928: 519–520 , fig. 61.

Cubitermes congoensis – Snyder 1949: 158. — Krishna et al. 2013: 1918. — Josens & Deligne 2019: 60–61 .

Isognathotermes congoensis – Hellemans et al. 2021: 233.

This species is suspected to be a junior synonym of Isognathotermes bulbifrons .

Diagnosis

The worker has a finitimus EVA and is among the smallest workers of the genus Isognathotermes ( Fig. 30).

The soldier is among the smallest in the genus Isognathotermes ( Fig. 28); the soldiers of I. fungifaber are sometimes as small but have a fungifaber EVA ; the soldier of I. phalloides sp. nov. (also with a finitimus EVA ) is sometime as small but has another, characteristic caecum.

The imago is unknown.

This species is also defined by its chorology: the two known samples come from forested regions up to about 200 km from the Atlantic coast ( Fig. 38).

Etymology

The name congoensis (from Congo and the Latin desinence - ensis, ‘from’) clearly refers to the country of type locality (“ Belgian Congo ”, now DRC).

Material examined

Three samples from two locations (probably from two colonies), all identified as C. congoensis .

Paratypes of Cubitermes congoensis Emerson, 1928

DEMOCRATIC REPUBLIC OF THE CONGO • soldier, worker; Banana ; 5°58′ S, 12°26′ E; Aug. 1915; Lang-Chapin leg.; study code: DJ 0299; initially C. congoensis ; AMNH • soldier, worker; Banana ; 6°1′ S, 12°25′ E; Aug. 1915; Lang-Chapin leg.; study code: DJ 0484; initially C. congoensis ; PPRI, ISTM 5690 .

Krishna et al. (2013: 1918) mention that the holotype is deposited in AMNH, not examined.

Other material examined

CAMEROON • soldier, worker; Mbalmayo ; 3°31′ N, 11°30′ E; Mar. 1996; P. Eggleton et al. leg.; study code: DJ 0648; initially C. congoensis ; NHMUK 13671845 .

Historical review

Emerson (1928: 519–520) described this taxon under the name Mirotermes ( Cubitermes) congoensis . He provided a description (text, measurements, and figure) of the soldier, mentioning differences with other species.

Snyder (1949: 158) catalogued this taxon under the name Cubitermes congoensis in the sub-family Termitinae and reported its known geographical distribution.

Krishna et al. (2013: 1918) housed C. congoensis in the sub-family Cubitermitinae .

Josens & Deligne (2019: 42–44) placed this taxon in the finitimus valve pattern group.

Hellemans et al. (2021: 233) placed this taxon in the restored genus Isognathotermes . The sample, however, could not be sequenced.

The validity of Isognathotermes congoensis , is puzzling: it has been found in two remote places: the type colony (DJ 0299 & DJ 0484) near the mouth of the Congo River, DRC, and another sample near Mbalmayo, Cameroon (DJ 0648). As explained in the chapter bulbifrons , four samples from incipient or very young colonies collected by N.M. Collins near Douala, Cameroon, were identified on the basis of their young queens as being I. bulbifrons ; if the soldiers had been used instead, the resulting identification would have been I. congoensis . In the PCA on soldier morphology, those soldiers join the soldiers from I. congoensis colonies (ellipse labelled “c+b” in Fig. 22). Therefore, the two samples identified as I. congoensis might also be incipient colonies of I. bulbifrons . This hypothesis is supported by the absence of imagines. This name might become a synonym if it turns out that it was assigned to an incipient colony of I. bulbifrons .

Redescription

Imago

The imago is unknown.

Soldier

COLOUR. Head capsule C4–C5 becoming fader and darker (Cf5–Cf6) in long preserved samples. Gulamentum concolorous with head. Antennae and labrum paler (C3–C4) than head capsule, darker in long preserved samples. Mandibles dark (C7) with an abrupt clearing on their bases (C5–C6) which is same colour as frons. Thorax, nota and legs paler than head capsule (C2–C4), darker in long preserved samples. Abdomen grey owing to digestive bolus.

SETATION. Head capsule with few scattered fine setae; on frons a scattered bunch of setae surrounds and overhangs fontanelle (but one sample with very few setae around fontanelle). Antennae with some prominent setae, 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). Labrum always with some large setae on lobes. Thorax: pro- and mesonotum with some setae mainly located on margins. Legs: fore coxa furnished with only one large seta on carina; fore trochanter generally with five or six aligned setae; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively; all tibiae furnished with a row of 4–6 spines. Abdomen: tergites with some large setae, mainly on their posterior margins. Sternites with long setae, erect or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 19; Fig. 28). Size: the soldiers of I. congoensis are, on average, clearly among the smallest of the genus Isognathotermes ; this is better seen in the soldiers’ head lengths ( Fig. 29). Head capsule: clearly sclerotised and appreciably longer than wide. Dorsal view: lateral sides subparallel, slightly convex to narrowed near posterior third or fourth, converging slightly towards anterior until antennal sockets; from antennal sockets sides converge towards bases of mandibles; posterior side rounded. In profile: clearly concave; frons with a faint frontal hump overhanging the fontanelle or no hump at all. Gulamentum in ventral view constricted in its posterior half, with sides of anterior part convex; rounded or with a slightly concave, posterior part from side view. Antennae: of 14.5 or 15 articles. Labrum: deeply bifurcate, with lyre-shaped sides; lobes angular or subtruncated, 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, with entire 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 posterior half of abdomen. Arrangement of enteric valve cushions showing trilateral symmetry: the odd cushions being somewhat longer and wider than the even cushions; the odd cushions with crests weakly developed; secondary cushions wide at the upstream end narrowing noticeably downstream with a homogeneous spine scattering. Caecum best seen in ventral view, near centre of abdomen, with three faint lobes.

Worker

The description of the worker is given here for the first time.

COLOUR. Head capsule pale (C2–C3) turning grey in long preserved samples. Antennae: proximal articles pale (C2), distal articles darker (C3). Thorax, nota and legs pale (C1–C2). 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 0–2 on ventral side; fore trochanter with six spines; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of five to six 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 19, Fig. 30). Size: the workers of I. congoensis are, on average, among the smallest of the genus Isognathotermes : Fig. 30. Head capsule weakly sclerotised (except mandibles). Antennae 14–14.5 articles. Labrum: cupola shaped, wider than long. 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. 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 very high density of rather short bristles on a globular bulge; supporting bristles are numerous: 22–33 on each side of the odd PCs; secondary cushions are wide at the upstream end, narrowing noticeably downstream with a homogeneous spine scattering. Caecum rather small, visible in ventral view, near centre of abdomen, shortly lobed (small lobes, sometimes only sketched).

Chorology-ecology

The type of this species was collected near the mouth of the Congo River ( Fig. 38) and despite several collecting sessions in the Kongo-Central Province by A. Bouillon and his collaborators and by other entomologists, no other samples of this species have been found there.

However, a sample from Cameroon matches I. congoensis morphology.

Molecular data

No genetic sequence is currently available.