Isognathotermes minitabundus ( Sjöstedt, 1913 )

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 : 87-94

Isognathotermes minitabundus ( Sjöstedt, 1913)

Figs 2, 8–12, 26–31, 33, 48, distribution map: Fig. 49; Table 8

Eutermes ( Cubitermes) minitabundus Sjöstedt, 1913: 368–369 (soldier only).

Eutermes ( Trinervitermes) carbo – Sjöstedt 1924a: 42 (the alate imago described under this name actually belonged to Cubitermes minitabundus ). Isognathotermes minitabundus – Sjöstedt 1926: 216–217, fig. 48. — Hellemans et al. 2021: 233. Cubitermes minitabundus – Snyder 1949: 161. — Harris 1958: 13–14, figs 20–23. — Williams 1966:

90–92, figs 6, 22, 38, 54, 72. — Bouillon & Vincke 1971: 269. — Krishna et al. 2013: 1927. —

Josens & Deligne 2019: 60–61.

Diagnosis

This species is very close to I. ugandensis (and I. severus ).

The worker has a fungifaber EVA ( Fig. 4) but in 3% of the samples examined, it has an EVA intermediate between the fungifaber and finitimus patterns. It is among the medium-sized workers of the genus Isognathotermes ( Fig. 30). As in I. ugandensis , the premolar tooth on left mandible is more apparent than in most other species.

The soldier is among the large-sized soldiers in the genus Isognathotermes ( Fig. 28), on average somewhat larger than that of I. ugandensis ; it has a left mandible very slightly curved to almost straight at the base and generally less curved than the right mandible (SMlc/SMrc = 0.51–1.03, with a weaker asymmetry than in I. ugandensis : SMlc/SMrc = 0.92–1.14), resulting in a low soldiers’ left mandible apical curvature index ( Fig. 29); its head is generally clearly bulbous (but this is shared with I. ugandensis and I. severus , and also with I. bulbifrons which has a finitimus EVA ).

The imago is among the medium- to large-sized imagines in the genus Isognathotermes ( Figs 26, 65); the eyes and ocelli are relatively small, as a consequence, the eye to ocellus minimal distance index is high: IEyOcD/IOc d = 1.16–1.61 (vs 0.54–1.58 in I. ugandensis ). The premolar tooth on left mandible is better seen than in most other species (but this is shared with I. severus and I. ugandensis ).

This species is also defined by its ecology and chorology: it is the southernmost species of the genus Isognathotermes , it has been found in forest-savannah mosaics and woodlands (miombo) to the south and east of the Congolian forests ( Fig. 49).

Etymology

The epithet minitabundus from the Latin minitabundus (threatening) probably refers to a supposed threat.

Material examined

Thirty-six samples from 15 locations. Of the 24 old museum samples, 18 were initially labelled as C. minitabundus , four as C. ugandensis , one as Eutermes fungifaber and one as Cubitermes sp.

Syntype of Eutermes ( Cubitermes) minitabundus ( Sjöstedt, 1913)

DEMOCRATIC REPUBLIC OF THE CONGO • soldier; Lumata ; 12°0.05′ S, 27°31′ E; 6 Jun. 1912; J. Bequaert leg.; study code: DJ 0129; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059280 .

Other material examined

DEMOCRATIC REPUBLIC OF THE CONGO • soldier, worker; Hemptine Saint Benoît [= Bunkonde]; 6°18′ S, 22°31′ E; 1912; P. Callewaert leg.; study code: DJ 0140; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059284 • soldier, worker, ♀ (queen); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 21 Jan. 1912; P. Callewaert leg.; study code: DJ 0094; initially Eutermes fungifaber in RMCA; BE RMCA INS. Iso. 059274 • soldier, worker; Hemptine Saint Benoît [= Bunkonde]; 6°18′ S, 22°32′ E; 26 Jan. 1912; P. Callewaert leg.; study code: DJ 0015; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059286 • soldier, worker, ♀ (queen); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 26 Oct. 1921; P. Callewaert leg.; study code: DJ 0139; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059283 • soldier, worker, ♀ (queen); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 26 Oct. 1921; P. Callewaert leg.; study code: DJ 0157; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059276 • soldier, worker, ♀ (alate), ♂ (alate), ♀ (queen); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 27 Oct. 1921; P. Callewaert leg.; study code: DJ 0144; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059285 • soldier, worker, ♀ (alate), ♂ (alate), ♀ (queen); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 27 Oct. 1921; P. Callewaert leg.; study code: DJ 0155; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059278 • soldier, worker, ♀ (alate), ♂ (alate), ♀ (queen); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 27 Oct. 1921; P. Callewaert leg.; study code: DJ 0156; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059275 • soldier, worker, ♀ (alate); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 27 Oct. 1921; P. Callewaert leg.; study code: DJ 0158; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059277 • soldier, worker, ♀ (alate); Luluabourg [= Kananga]; 5°53′ S, 22°26′ E; 27 Oct. 1921; P. Callewaert leg.; study code: DJ 0728; initially C. minitabundus ; AMNH • soldier, worker; Upemba N.P., Lusinga ; 8°56.4′ S, 27°8′ E; 17 Jul. 1947; G.F. De Witte et al. leg.; study code: DJ 0137; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059282 • soldier, worker, ♂ (king), ♀ (queen); Upemba N.P., Lusinga ; 8°56.4′ S, 27°8′ E; 17 Jul. 1947; G.F. De Witte et al. leg.; study code: DJ 0138; initially C. minitabundus in RMCA; BE RMCA INS. Iso. 059281 • soldier, worker, ♂ (king); Keyberg ( Lubumbashi); 11°47′ S, 27°25′ E; 21 Apr. 1948; A. Emerson leg.; study code: DJ 0729; initially C. minitabundus in AMNH • soldier, worker, ♂ (king); Likasi ; 10°59.3′ S, 26°4.27′ E; 1 Dec. 1971; P. Vincke leg.; study code: DJ 0898; initially C. ugandensis in RMCA; BE RMCA INS. Iso. 059271 • soldier, worker, ♂ (alate); Kundelungu P.N.; 10°27′ S, 27°42′ E; 15 Oct. 1972; P. Vincke leg.; study code: DJ 0899; initially Cubitermes sp. in RMCA; BE RMCA INS. Iso. 059272 • soldier, worker; Kipopo ; 11°33′ S, 27°21′ E; 2 Nov. 1972; P. Vincke leg.; study code: DJ 0908; initially C. ugandensis in RMCA; BE RMCA INS. Iso. 059273 • soldier, worker; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.3′ E; 11 Feb. 2011; G. Josens leg.; study code: DJ 0010; BE RMCA INS. Iso. 059279 • soldier, worker; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.3′ E; Jun. 2016; P. Kasangij leg.; study code: DJ 0348; GenBank nos MN646704 ( COI), MN685906 ( COII), MN685967 ( 28S), PQ679238 (mitogenome); BE RMCA INS. Iso. 059270 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.3′ E; 3 Jun. 2016; P. Kasangij leg.; study code: DJ B008; BE RMCA INS. Iso. 059259 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.3′ E; 3 Jun. 2016; P. Kasangij leg.; study code: DJ B009; GenBank no PQ679225 (mitogenome); BE RMCA INS. Iso. 059260 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.3′ E; 3 Jun. 2016; P. Kasangij leg.; study code: DJ B010; BE RMCA INS. Iso. 059261 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.3′ E; 3 Jun. 2016; P. Kasangij leg.; study code: DJ B011; BE RMCA INS. Iso. 059262 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.18′ E; 14 Jun. 2016; P. Kasangij leg.; study code: DJ B012; BE RMCA INS. Iso. 059263 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.18′ E; 14 Jun. 2016; P. Kasangij leg.; study code: DJ B014; BE RMCA INS. Iso. 059264 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.2′ E; 14 Jun. 2016; P. Kasangij leg.; study code: DJ B017; BE RMCA INS. Iso. 059265 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.2′ E; 14 Jun. 2016; P. Kasangij leg.; study code: DJ B018; BE RMCA INS. Iso. 059266 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.2′ E; 22 Jun. 2016; P. Kasangij leg.; study code: DJ B019; BE RMCA INS. Iso. 059267 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.2′ E; 22 Jun. 2016; P. Kasangij leg.; study code: DJ B020; BE RMCA INS. Iso. 059268 • soldier; Kisangwe , Mikembo sanctuary; 11°29.1′ S, 27°39.2′ E; 2 Jul. 2016; P. Kasangij leg.; study code: DJ B021; BE RMCA INS. Iso. 059269 .

ZAMBIA • soldier, worker; Kitwe , Mwekera Forest reserve; 12°52′ S, 28°21′ E; 25 Jan. 1956; W.G.H. Coaton leg.; study code: DJ 0696; initially C. minitabundus ; NHMUK 13671922 • soldier, worker; Samfya ; 11°22′ S, 29°33′ E; 27 Jan. 1957; W.G.H. Coaton leg.; study code: DJ 0665; initially C. ugandensis ; NHMUK 13672010 • soldier, worker; Chembe ; 11°57.5′ S, 28°44′ E; 28 Jan. 1957; W.G.H. Coaton leg.; study code: DJ 0685; initially C. minitabundus ; NHMUK 13671920 • soldier; Ndola–Kitwe road; 12°59′ S, 28°24.5′ E; 30 Jan. 1957; W.G.H. Coaton leg.; study code: DJ 0694; initially C. minitabundus ; NHMUK 13671921 • soldier, worker; Kasama–Mpika road; 11°0′ S, 31°0′ E; 19 Dec. 1969; M.G. Bingham leg.; study code: DJ 0695; initially C. minitabundus ; NHMUK 13671925 • soldier, worker; Chililabombwe ; 12°23′ S, 27°50′ E; 22 Dec. 1970; M.G. Bingham leg.; study code: DJ 0693; initially C. minitabundus ; NHMUK 13671926 .

Historical review

Sjöstedt (1913: 368–369) described the soldier of his species under the name Eutermes ( Cubitermes) minitabundus .

Schmitz (1916: 119) referred to this species under the name Cubitermes minitabundus .

Sjöstedt (1924a: 42) described the imago of Eutermes ( Trinervitermes) carbo that was in fact the imago of Cubitermes minitabundus (see Sands 1965: 98 and Krishna et al. 2013: 1858).

Sjöstedt (1926: 216–217) transferred the species in a new, monotypic genus ( Isognathotermes ). He provided figures of the soldier and a description of imago and worker.

Snyder (1949: 161) catalogued this species under the name Cubitermes minitabundus and housed it in the sub-family Termitinae .

Harris (1958: 13–14) provided measurements and figures of imago and soldier on basis of specimens collected in the Upemba National Park (Haut-Katanga Province, DRC).

Williams (1966: 90–92) provided a detailed redescription of imago and soldier along with measurements and figures.

Bouillon & Vincke (1971: 269) described the enteric valve of C. minitabundus as belonging to the first of three types, the “simple type ” without any spatula.

Krishna et al. (2013: 1927) referred to this species under the name Cubitermes minitabundus and housed it in the sub-family Cubitermitinae .

Josens & Deligne (2019: 39–42) placed this species within the fungifaber valve pattern group.

Hellemans et al. (2021: 233) placed this species in the restored genus Isognathotermes .

Redescription

Imago

COLOUR. Head capsule: well sclerotised, fresh samples very dark, C6–C8 (C5–C 7 in long preserved samples); fontanelle concolorous or almost so with head capsule. Postclypeus C5–C7 concolorous or slightly paler (one level) than head capsule. Antennae C4–C6 without any difference between proximal and distal articles. Thorax: pronotum C5–C7, as postclypeus, concolorous or one level paler than head capsule; meso- and metanotum C4–C7, sometimes somewhat paler than pronotum. Legs C3–C5; tibia usually concolorous with femur. Wings hyaline with brown to grey tinge (Cf2–Cf3), anterior veins darker. Abdomen: tergites C4–C6. Sternites appreciably paler in middle (C2–C3) with both sides darker (C3–C4); posterior sternites darker (C3–C4) 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 20–80 ×, but rarely even not visible at 80 ×; when present, these fine setae do not extend over the posterior margin; sometimes a small number of large setae are present on metanotum. Legs very pilose, furnished (among numerous fine setae) with some stronger setae: 8–12 on the carina of fore coxa and 0–6 on the ventral side of fore coxa and trochanter; tibia pilose fore, mid, and hind tibia furnished with 20–40 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 8; Fig. 48). Size: the imagines of I. minitabundus are among the medium- to large-sized species of the genus Isognathotermes (as I. ugandensis ) ( Fig. 26). Head capsule: compound eyes nearly round to oval; ocelli shortly to moderately oval, removed from eyes with a higher eye to ocellus minimal distance index: IEyOcD/IOc d = 1.16–1.61 ( 0.54–1.58 in I. ugandensis ); fontanelle generally a tiny round or elongate marking. Antennae: 16 articles on alate individuals, always shortened by amputation by two to five articles in queens and kings. Labrum: cupola shaped, wider than long. Left mandible with apical tooth medium to large sized (IMlAmD = 0.21–0.27 mm vs 0.19–0.27 in I. ugandensis , 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 with proximal end hardly 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 carina. Wings: R1 fused entirely with costal margin, sclerotised; Rs simple, sclerotised; M and Cu not or weakly sclerotised with 2–4 and 10–12 branches, respectively. Gut not studied.

Soldier

COLOUR. Head capsule generally tending towards deep palette (Cd4–Cd6) becoming fader (Cf4–Cf5) in long preserved samples; there is generally a smooth gradient from a darker frons to a paler back. Antennae and labrum generally one to two palette levels paler than head capsule. Mandibles dark (C6– C8) generally with an abrupt clearing on their bases (two levels) which is generally the same colour as frons; in long preserved samples, this clearing tends to disappear. Thorax and legs paler than head capsule (C3–C5) somewhat darker in long preserved samples. 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 5–8 large setae on each lobe. Thorax: pro- and mesonotum with a small number of setae mainly located on margins. Legs: fore coxa bears at least one fine seta and 1–3 spines (exceptionally 5) on carina and not any spine on ventral side; trochanter generally with some strong lined-up setae, or with 3–7 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 7–18 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 8; Fig. 48). Size: the soldiers of I. minitabundus are part of the medium to larger soldiers in the genus Isognathotermes ( Fig. 28). Head capsule: always clearly sclerotised; appreciably longer than wide. Dorsal view: lateral sides mostly subparallel with a clear or slight narrowing near posterior third or fourth; from antennal sockets sides converge towards bases of mandibles; posterior side regularly convex or sometimes with short straight or even concave parts. In profile: upper profile always slightly to strongly concave; angle between extended mandibles and frons obtuse; frons with an outlined or clear anterior hump. Gulamentum in ventral view always constricted in its posterior half, with sides of anterior part either roundly convex or more frequently forming an acute widening or even a kind of ear on each side. Antennae: of 14–15 articles. Labrum: always deeply bifurcate and wider than long, with sides varying from lyre-shaped (in 87% of the samples examined) to almost straight; lobes angular, frequently with fine, whitish, or translucent tips; anterior margin concave. Mandibles: sabre-like and rather clearly asymmetrical, the left mandible is slightly curved to almost straight and hooked distally and obviously less curved than the right mandible; inner edges generally smooth with one distinct but very small marginal tooth, near molar tooth on each mandible; mandibles clearly shorter than head; entire surface of both mandibles smooth and glossy. Right mandible always clearly more curved than left. Thorax: pronotum sellate, as wide as 52–61% of head width, with straight or indented anterior margin and posterior straight margins. Fore coxa flanged ventrally resulting in a more or less sharp carina. Gut: enteric valve seating on left side, best seen in ventral view, situated in second half of abdomen. Caecum always rather small, best seen in ventral view, near centre of abdomen, three-lobed. Arrangement of enteric valve cushions showing trilateral symmetry, the odd cushions being about 18% longer than the even cushions, generally without any crest or with crests very weakly developed.

Worker

COLOUR. Head capsule pale (C1–C3) turning grey in long preserved samples. Antennae: proximal articles pale (C2–C3), distal articles always one to two levels darker (C4–C5). Thorax, nota, and legs pale (C1–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 always carinated, bearing one fine seta and furnished with 4–6 spines on carina and 0–2 on ventral side; fore trochanter with 6–8 spines, all except one lined up; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of 8–18 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 8, Fig. 48). Size: the workers of I. minitabundus are part of the medium-sized workers in the genus Isognathotermes (with large overlapping on several other species: Fig. 30). Head capsule: weakly sclerotised (except mandibles). Antennae of 14.5 (sometimes 14) articles. Labrum: cupola shaped. Left mandible: apical tooth well developed with a sharp tip when fresh; marginal teeth three in number, first marginal tooth well developed but with a blunt tip even when fresh, second marginal appearing as an undulated edge, reduced but still present in worn mandibles (more visible than in other species), third marginal tooth with a blunt tip; premolar tooth generally well visible (more than in other species); 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 and frequently with a wavy inner edge near the base; 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 sellate, as wide as 65–70% 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 second half of abdomen. Arrangement of enteric valve cushions of the fungifaber pattern with triradial symmetry: the odd PCs, in their downstream part, are rather narrow and bear crests that are as high as or higher than they are wide, with long and strong bristles; 15–26 supporting bristles 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, generally with three to five short lobes.

Chorology-ecology

The geographic distribution of I. minitabundus is linked with the southern Congolian forest-savanna mosaic and the Central Zambezian Miombo woodland ecoregions; this is, with I. ugandensis malawii subsp. nov., the southernmost species of the genus Isognathotermes ( Fig. 49).

Molecular data

The species I. minitabundus was previously referred to as “I. afug” (DJ 0348) by Hellemans et al. (2021), which was identified as a close species to I. ugandensis . Herein, we recognise this sample to belong to its own species, due to distinct morphologies and geographical distributions.

Two mitogenomes of this species (both collected from Kisangwe, DRC, Haut-Katanga Province) are published alongside this work (GenBank accessions: see Supp. file 3 and ‘Material examined’).

The difficulty of morphological delimitation between I. minitabundus and I. ugandensis is also reflected from analyses of their mitogenomes, with I. minitabundus placed as sister to I. ugandensis in a phylogenetic reconstruction ( Fig. 33), and with whom they exhibit on average less than 2% dissimilarity (Supp. file 4). However, they also exhibit less than 2% dissimilarity with I. finitimus (Supp. file 4).