Isognathotermes finitimus ( Schmitz, 1916 )

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 : 56-66

Isognathotermes finitimus ( Schmitz, 1916)

Figs 5, 13–20, 22, 26–33, 39–41, distribution map: Fig. 38; Table 4

Cubitermes finitimus Schmitz, 1916: 120–124 , figs 1–2.

Cubitermes speciosus Sjöstedt, 1924b: 256 . Syn. nov.

Mirotermes ( Cubitermes) subarquatus Emerson, 1928: 510–511 , pl. XXIX fig. 55.

Cubitermes finitimus – Sjöstedt 1926: 221–226. — Snyder 1949: 159. — Bouillon & Vincke 1971: 269. — Krishna et al. 2013: 1920. — Josens & Deligne 2019: 60–61 , figs 11, 16.

Cubitermes subarquatus – Krishna et al. 2013: 1938.

Isognathotermes finitimus – Hellemans et al. 2021: 231–233.

Diagnosis

As already pointed out by H. Schmitz (1916), a soldier or an imago alone does not allow a confident identification. Indeed, this species is difficult to identify from its morphology since it is in a medium position in the genus Isognathotermes (blue ellipse in the middle of Fig. 22).

It is obviously easier to identify this species from its mitogenome: I. finitimus makes a clade well apart from the planifrons clade ( Hellemans et al. 2021: 231).

If molecular data are not available, the best recognition is reached by a combination of worker’s EVA, soldiers’ mandibles, and geographical origin.

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

The soldier is also medium sized in the genus Isognathotermes ( Fig. 28; SHdL = 2.70–3.45 mm), and its EVA can generally be recognized as a finitimus EVA. The forehead has little, or no prominence, and the upper profile is only slightly concave. In comparison with I. planifrons , it has, on average, a higher acceleration of the mandible curvature: ln(SMlpR) - ln(SMldR) = 1.28–2.42 ( 0.89–2.28 in I. planifrons ), that means: mandibles less curved at the base and more so at the tip. In I. planifrons , the soldier has on average slightly more curved mandibles.

The imago is also medium sized ( Fig. 26) in the genus Isognathotermes (IHdW = 1.47–1.71 mm).

This medium-sized species can be confused with several other species with a finitimus EVA : I. planifrons and I. bulbifrons ( I. phalloides sp. nov. and I. phallicaecalis sp. nov. have also similar sizes and morphologies but they can be distinguished easily by their caecum).

Isognathotermes finitimus can also be characterized by its ecology and chorology: it has always been found in continental forests east of longitude 15°E (but the I. finitimus and I. planifrons areas overlap in the south-west of CAR ( Figs 38, 47); other species with a finitimus EVA can be found in this area: I. magniplanifrons sp. nov. with distinctly larger soldiers or I. phallicaecalis sp. nov. and I. phalloides sp. nov. with a characteristic, different caecum.

Etymology

The epithet finitimus from the Latin finitimus (bordering, close to) doubtless refers to the proximity of C. finitimus with both C. fungifaber and C. zenkeri , discussed at length by Schmitz in the original description.

Material examined

Sixty samples from 24 locations. Of the 35 old museum samples examined, nine samples were initially labelled as Cubitermes finitimus , four as C. fungifaber , one as C. fungifaber var. elongata , one as C. loubetsiensis , six as C. minitabundus , 11 as C. speciosus , two as C. subarquatus , and one as Cubitermes sp.

Syntype of Cubitermes finitimus Schmitz, 1916

DEMOCRATIC REPUBLIC OF THE CONGO • ♀ (queen); Stanleyville [= Kisangani]; 0°31′ N, 25°12′ E; before 1904; H. Kohl leg.; study code: DJ 0291; initially C. finitimus → C. fungifaber ; AMNH.

Syntypes of Cubitermes speciosus Sjöstedt, 1924

DEMOCRATIC REPUBLIC OF THE CONGO • soldier, worker, ♀ (queen); Moto; 2°54.47′ N, 29°24.85′ E; 1923; L. Burgeon leg.; study code: DJ 0061; initially C. speciosus in RMCA; BE RMCA INS. Iso. 059178 .

Krishna et al. (2013: 1937) mention that other syntype samples are deposited in AMNH and PPRI, not examined.

Syntypes of Cubitermes subarquatus Sjöstedt, 1926

DEMOCRATIC REPUBLIC OF THE CONGO • soldier, ♂ (alate); Stanleyville [= Kisangani]; 0°31′ N, 25°12′ E; before 1904; H. Kohl leg.; study code: DJ 0803; initially C. subarquatus → C. finitimus ; AMNH, IZC 00321262.

This latter label (DJ 0803) has been amended: on the one hand Emerson (1928: 510–511) mentioned for this sample: “Lubila River, Belgian Congo: Lang-Chapin Coll., Sept. 20, 1919 ” but in his introduction he wrote: “the collection was made by Mr. Herbert Lang and Mr. James P. Chapin during the American Museum Congo expedition, 1909–1915,…”: this period does not include the collecting date of September 1919. On the other hand, the photo of the nest (plate XXIX) is dated “ September 20, 1909 ”, which is consistent with the dates of the Lang-Chapin expedition. In agreement with Sjöstedt (1926: 244), we changed the label to: “Stanleyville [= Kisangani], H. Kohl coll. [Date unknown, probably before 1904]”.

Krishna et al. (2013: 1938) mention that another syntype sample is deposited in PPRI, not examined.

Other material examined

CENTRAL AFRICAN REPUBLIC • soldier, worker; Lobaye rain forest; 4°5′ N, 17°0′ E; 1975; G. Becker leg.; study code: DJ 0680; initially C. speciosus ; NHMUK 13671988 • soldier; near Bangui; 4°16′ N, 18°31′ E; 1975; G. Becker leg.; study code: DJ 0679; initially C. speciosus ; NHMUK 13671989 .

DEMOCRATIC REPUBLIC OF THE CONGO • soldier, ♀ (alate); Sankuru; 3°57′ S, 21°48′ E; [no date]; unknown leg.; study code: DJ 0279; initially C. fungifaber var. elongata ; AMNH • soldier, worker, ♀ (queen); unclear data: “Lubila R.”; 1°0′ N, 27°10′ E; 20 Sept. 1919 or Stanleyville [= Kisangani]; 0°31′ N, 25°12′ E; before 1904; H. Kohl leg.; study code: DJ 0295; initially C. subarquatus → C. finitimus ; AMNH • soldier, worker; Irumu–Avakubi road; 1°21′ N, 29°6′ E; Oct. 1906; unknown leg.; study code: DJ 0677; initially C. subarquatus ; NHMUK 13671992 • soldier, worker; Medje; 2°25′ N, 27°18′ E; Jun. 1914; Lang-Chapin leg.; study code: DJ 0122; initially C. loubetsiensis in RMCA; BE RMCA INS.Iso.059177 • soldier, ♀ (queen); Medje; 2°25′ N, 27°18′ E; Jun. 1914; Lang Chapin leg.; study code: DJ N125; initially C. fungifaber ; AMNH • soldier, worker; Medje; 2°25′ N, 27°18′ E; Jul. 1914; Lang-Chapin leg.; study code: DJ 0612; initially C. finitimus ; AMNH • soldier, worker; unclear location “Lubila R.”; [ 1°0′ N, 27°10′ E?]; 20 Sep. 1919; Lang-Chapin leg.; study code: DJ 0064; initially C. subarquatus in RMCA; BE RMCA INS.Iso.059182 • soldier, worker; Moto; 3°2′ N, 29°30′ E; 1922; L. Burgeon leg.; study code: DJ 0166; initially C. speciosus in RMCA; BE RMCA INS.Iso.059179 • soldier, ♀ (alate), ♂ (alate), ♀ (queen); Moto; 3°2′ N, 29°30′ E; 1923; L. Burgeon leg.; study code: DJ 0071; initially C. speciosus in RMCA; BE RMCA INS.Iso.059180 • soldier, worker, ♀ (alate), ♂ (alate); Moto; 3°2′ N, 29°30′ E; 1923; L. Burgeon leg.; study code: DJ 0072; initially C. speciosus in RMCA; BE RMCA INS.Iso.059181 • soldier, worker, ♀ (alate), ♀ (queen); Epulu; 1°24′ N, 28°36′ E; 2 May 1948; A. Emerson leg.; study code: DJ 0613; initially C. finitimus ; AMNH • soldier, worker, ♀ (queen); Epulu; 1°24′ N, 28°36′ E; 12 May 1948; A. Emerson leg.; study code: DJ 0618; initially C. finitimus ; AMNH • soldier, worker; Epulu; 1°24′ N, 28°36′ E; 12 May 1948; A. Emerson leg.; study code: DJ 0619; initially C. finitimus ; AMNH • soldier, worker, ♀ (queen); Epulu; 1°24′ N, 28°36′ E; 13 May 1948; A. Emerson leg.; study code: DJ 0617; initially C. finitimus ; AMNH • soldier, worker, ♀ (queen); Epulu; 1°24′ N, 28°36′ E; 15 May 1948; A. Emerson leg.; study code: DJ 0286; initially C. finitimus ; AMNH • soldier, ♀ (queen); Yangambi; 0°48′ N, 24°29.3′ E; 29 May 1948; A. Emerson leg.; study code: DJ N127; initially C. fungifaber ; AMNH • soldier, ♂ (king); Stanleyville [= Kisangani]; 0°31′ N, 25°11′ E; 1 Jun. 1948; A. Emerson leg.; study code: DJ N128; initially C. fungifaber ; AMNH • soldier, ♀ (queen); Stanleyville [= Kisangani]; 0°31′ N, 25°12′ E; 1 Jun. 1948; A. Emerson leg.; study code: DJ 0616; initially C. finitimus ; AMNH • soldier, ♂ (king); Mondongo; 2°16.5′ N, 19°9.4′ E; 13 Sep. 1966; J. Ruelle leg.; study code: DJ B318; initially C. minitabundus in RMCA; BE RMCA INS.Iso.059173 • soldier, worker; near Mongolo; 2°14′ N, 19°12′ E; 14 Sep. 1966; J. Ruelle leg.; study code: DJ 0874; initially C. minitabundus in RMCA; BE RMCA INS.Iso.059170 • soldier, worker; Beronge; 1°30′ S, 19°0′ E; 18 Sep. 1966; P. Cappelle leg.; study code: DJ 0897; initially C. minitabundus in RMCA; BE RMCA INS.Iso.059176 • soldier, worker; Yalosemba; 2°34.5′ N, 21°47.5′ E; 24 Sep. 1966; J. Ruelle leg.; study code: DJ 0876; initially C. minitabundus in RMCA; BE RMCA INS.Iso.059174 • soldier, worker, ♂ (king); Yalosemba; 2°34.5′ N, 21°47.5′ E; 24 Sep. 1966; J. Ruelle leg.; study code: DJ 0877; initially C. minitabundus in RMCA; BE RMCA INS.Iso.059175 • soldier, worker, ♀ (queen); Mondongo; 2°16.5′ N, 19°9.4′ E; 27 Sep. 1966; unknown leg.; study code: DJ 0875; initially C. minitabundus in RMCA; BE RMCA INS.Iso.059171 • soldier, worker; Irangi; 1°54′ S, 28°27′ E; 1 Apr. 1972; A. Bouillon leg.; study code: DJ 0878; initially Cubitermes sp. in RMCA; BE RMCA INS.Iso.059172 • soldier, worker, ♀ (queen); Kisangani, Masako reserve; 0°38′ N, 25°15′ E; 1990; K. Soki leg.; study code: DJ 0012; BE RMCA INS.Iso.059169 • soldier, worker, ♀ (queen); Yaekela; 0°49.12′ N, 24°16.67′ E; 2 May 2010; B. Le Ru leg.; study code: DJ 0739; GenBank no PQ679218 (mitogenome); BE RMCA INS.Iso.059166 • soldier, worker, ♂ (king); Bomane; 1°15.74′ N, 23°42.4′ E; 19 May 2010; B. Le Ru leg.; study code: DJ 0741; GenBank no PQ679248 (mitogenome); BE RMCA INS.Iso.059168 • soldier, worker; Lokulu; 1°14.12′ N, 23°43.19′ E; 22 May 2010; B. Le Ru leg.; study code: DJ 0742; GenBank no PQ679241 (mitogenome); BE RMCA INS.Iso.059167 • soldier, worker; Yangambi; 0°52.9′ N, 24°19.5′ E; 3 Jul. 2013; Y. Roisin leg.; study code: DJ 0086; GenBank nos MN646708 ( COI), MN685910 ( COII), MN685971 ( 28S); BE RMCA INS.Iso.059183 • soldier, worker; Yangambi; 0°47.369′ N, 24°31.08′ E; 5 Jul. 2013; Y. Roisin leg.; study code: DJ 0652; GenBank nos MN646709 ( COI), MN685911 ( COII), MN685972 ( 28S); BE RMCA INS.Iso.059184 • soldier; Yangambi; 0°52.957′ N, 24°19.475′ E; 8 Jul. 2013; Y. Roisin leg.; study code: DJ Y143; BE RMCA INS.Iso.059163 • soldier, worker; Yangambi; 0°47.369′ N, 24°31.08′ E; 9 Jul. 2013; Y. Roisin leg.; study code: DJ 0654; BE RMCA INS.Iso.059186 • soldier, worker; Yangambi; 0°47.151′ N, 24°31.437′ E; 10 Jul. 2013; Y. Roisin leg.; study code: DJ 0655; GenBank no PQ679174 (mitogenome); BE RMCA INS.Iso.059187 • soldier; Yangambi; 0°46.851′ N, 24°31.255′ E; 11 Jul. 2013; Y. Roisin leg.; study code: DJ Y147; BE RMCA INS.Iso.059164 • soldier; Yangambi; 0°46.851′ N, 24°31.255′ E; 11 Jul. 2013; Y. Roisin leg.; study code: DJ Y148; BE RMCA INS. Iso.059165 • soldier, worker; Yangambi; 0°46.851′ N, 24°31.255′ E; 11 Jul. 2013; Y. Roisin leg.; study code: DJ 0656; GenBank no PQ679205 (mitogenome); BE RMCA INS.Iso.059188 • soldier, worker, ♀ (alate); Yangambi; 0°46.851′ N, 24°31.255′ E; 11 Jul. 2013; Y. Roisin leg.; study code: DJ 0657; GenBank no PQ679173 (mitogenome); BE RMCA INS.Iso.059189 • soldier; Yangambi; 0°48.152′ N, 24°29.258′ E; 15 Jul. 2013; Y. Roisin leg.; study code: DJ Y149; BE RMCA INS.Iso.059156 • soldier, worker; Yangambi; 0°48.152′ N, 24°29.268′ E; 15 Jul. 2013; Y. Roisin leg.; study code: DJ 0653; GenBank nos MN646710 ( COI), MN685912 ( COII), MN685973 ( 28S), PQ679167 (mitogenome); BE RMCA INS.Iso.059185 • soldier; Yangambi; 0°47.598′ N, 24°29.498′ E; 18 Jul. 2013; Y. Roisin leg.; study code: DJ Y144; BE RMCA INS.Iso.059157 • soldier, worker, ♂ (king); Yangambi; 0°47.598′ N, 24°29.498′ E; 18 Jul. 2013; Y. Roisin leg.; study code: DJ 0757; BE RMCA INS.Iso.059190 • soldier; Yangambi; 0°47.598′ N, 24°29.498′ E; 19 Jul. 2013; Y. Roisin leg.; study code: DJ Y145; BE RMCA INS.Iso.059158 • soldier; Yangambi; 0°47.598′ N, 24°29.498′ E; 19 Jul. 2013; Y. Roisin leg.; study code: DJ Y150; BE RMCA INS.Iso.059159 • soldier; Yangambi; 0°47.598′ N, 24°29.498′ E; 19 Jul. 2013; Y. Roisin leg.; study code: DJ Y151; BE RMCA INS.Iso.059160 • soldier; Yangambi; 0°47.598′ N, 24°29.498′ E; 19 Jul. 2013; Y. Roisin leg.; study code: DJ Y152; BE RMCA INS.Iso.059161 • soldier; Yangambi; 0°48.51′ N, 24°31.647′ E; 20 Jul. 2013; Y. Roisin leg.; study code: DJ Y146; BE RMCA INS.Iso.059162 • soldier, worker; Yangambi; 0°48.51′ N, 24°31.647′ E; 20 Jul. 2013; Y. Roisin leg.; study code: DJ 0620; GenBank no KY224569 (mitogenome); BE RMCA INS.Iso.059191 • soldier, worker, ♂ (king); Yangambi; 0°48.51′ N, 24°31.647′ E; 20 Jul. 2013; Y. Roisin leg.; study code: DJ 0758; BE RMCA INS.Iso.059192 • soldier, worker, ♂ (king); Yangambi; 0°48.51′ N, 24°31.647′ E; 20 Jul. 2013; Y. Roisin leg.; study code: DJ 0758; BE RMCA INS.Iso.059192.

UGANDA • soldier, ♀ (queen); Bugondo forest ; 1°46′ N, 31°35′ E; 1944; C.J. Eggding and W.V. Harris leg.; study code: DJ U086; initially C. speciosus ; NHMUK 13671980 • soldier, worker; Kawanda ; 0°25.23′ S, 32°32.43′ E; 6 Dec. 1949; W.V. Harris leg.; study code: DJ 0684; initially C. speciosus ; NHMUK 13671982 • soldier; Kampala – Fort Portal road; 0°22′ N, 32°16.5′ E; 3 Feb. 1955; R.M.C. Williams leg.; study code: DJ U088; initially C. speciosus ; NHMUK 13671981 • soldier, worker, ♀ (alate); Entebbe – Kampala road; 0°7.5′ N, 32°31.5′ E; 2 Jul. 1970; Kistner leg.; study code: DJ 0681; initially C. speciosus ; NHMUK 13671985 • soldier; Kisubi forest ; 0°7′ N, 32°30′ E; 12 Jul. 1970; Kistner leg.; study code: DJ U087; initially C. speciosus ; NHMUK 13671987 .

Historical review

Schmitz (1916: 120–124) described this species under the name Cubitermes finitimus . He provided a description and measurements of king, queen, and soldier, mentioning that imagines are like those of C. zenkeri while the soldier closely resembles the soldier of C. fungifaber .

Sjöstedt (1926: 221–226) included C. finitimus in his soldiers’ key of Cubitermes species and inserted it in a “ zenkeri -Gruppe” of Cubitermes species with relatively shorter soldier’s mandibles. He clarified some morphological differences between C. finitimus , C. zenkeri and C. fungifaber .

Snyder (1949: 159) catalogued this species under the name Cubitermes finitimus in the sub-family Termitinae and reported its known geographical distribution.

Emerson, in his unpublished “card catalog” considered C. subarquatus as a synonym of C. finitimus (quoted by Krishna et al. 2013: 1938): this is confirmed in this work.

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

Krishna et al. (2013: 1920) housed Cubitermes finitimus in the sub-family Cubitermitinae .

Josens & Deligne (2019: 42–44) choose this species as type of the finitimus valve pattern group.

Hellemans et al. (2021: 231–233) placed this species in the restored genus Isognathotermes and within a “ finitimus clade”.

Redescription

Imago

COLOUR. Head capsule: well sclerotised, dark when fresh, C6–C7, lighter in old, preserved samples (C4–C6); fontanelle concolorous with or somewhat paler than head capsule. Postclypeus C6–C7 slightly paler (one level) than head capsule. Antennae C5–C6 without any difference between proximal and distal articles. Thorax: pronotum C6–C7, concolorous with or somewhat paler than head capsule; meso- and metanotum C6–C7, as pronotum. Legs C4–C5. Wings hyaline with brown to grey tinge (Cf3–Cf4), anterior veins darker. Abdomen: tergites C6–C7. Sternites appreciably paler in middle (C3–C4) with both sides darker (C4–C6); posterior sternites darker (C4–C6) than anterior.

SETATION. Head capsule with some prominent setae, mainly near the eyes, and a higher density of shorter, finer setae everywhere. 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 many shorter ones in middle; meso- and metanotum with some fine, pale setae, arranged in a medio-longitudinal strip, generally visible at 20 to 80 ×, with frequently one to four larger setae on metanotum. Legs very pilose, frequently furnished (among numerous fine setae) with some strong setae: 6–10 on the carina of fore coxa and 0–2 on the ventral side of fore coxa; tibia pilose; fore, mid, and hind tibia furnished with 10–30 strong setae 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 4; Figs 26, 39). Size: the imagines of I. finitimus are, on average, medium sized in the genus Isognathotermes ; as shown in Fig. 26. Head capsule ( Fig. 39): compound eyes nearly round; fontanelle generally a tiny round to elongate marking; ocelli nearly round to oval, removed from eyes by a distance about equal to 0.7–1.5 ocellus small diameter. Antennae: 16 articles on alate individuals, always shortened by amputation by one-three articles in queens and kings. Labrum: cupola shaped. Left mandible with apical tooth always longer and more prominent than first marginal; marginal teeth three in number but second one only suggested by a slight undulation of edge between first and third marginal teeth (this undulation disappears in worn mandibles); only the apical tooth is acute in unworn specimens; premolar tooth with proximal end 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 longer and 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 more or less sharp carina. Wings: R1 fused entirely with costal margin, sclerotised; Rs simple, sclerotised; M and Cu not or weakly sclerotised with 2–4 and 10–15 branches respectively. Gut (only studied in some cases): enteric valve weakly developed and hardly comparable with workers’ and soldiers’ valves; odd PCs are slightly longer than even PCs ( Fig. 6). Caecum present as a small amorphous button.

Soldier

COLOUR. Head capsule generally Cd4–Cd6 becoming fader and darker (e.g., Cf5–Cf7) in long preserved samples; there is frequently a gradient from a darker frons to a paler back (e.g., from C6–C4) sometimes giving the impression that the head capsule is bicolorous ( Fig. 13). Gulamentum generally concolorous with head. Antennae and labrum slightly paler (half a level) than head capsule. Mandibles dark (C7–C8) generally with an abrupt clearing on their bases (two palette levels) which is generally the same colour as frons. Thorax, nota and legs paler than head capsule (C3–C4). Abdomen grey to red-brown owing to digestive bolus, rarely with a yellow tinge on tergites.

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 always with 3–6 large setae on each lobe. Thorax: pro- and mesonotum with some setae mainly located on margins. Legs: fore coxa furnished with 2–4 (rarely 1 or 5) spines on carina and not any one on ventral side; trochanter generally with some long lined-up setae, sometimes with 4–7 spines; 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 7–15 spines. 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 4; Figs 28, 40). Size: the soldiers of I. finitimus are medium sized in the genus Isognathotermes ; this can be seen in the soldiers’ head lengths ( Fig. 28). Head capsule ( Fig. 40): always clearly sclerotised and appreciably longer than wide. Dorsal view: lateral sides mostly subparallel with a slight to very slight narrowing near posterior third or fourth; from antennal sockets sides converge clearly towards bases of mandibles; posterior side variable. In profile: upper profile slightly to clearly concave; frons: fontanelle overhanged by a very small frontal hump (or sometimes no hump at all). Gulamentum in ventral view always constricted in its posterior half, with sides of anterior part either forming an acute widening or even a kind of ear on each side. Antennae: of 15 articles, rarely 14.5 or 14. Labrum: always deeply bifurcate and wider than long, with sides always more or less lyre-shaped; lobes angular, with fine, whitish, or translucent tips; anterior margin concave ( Fig. 40). Mandibles: sabre-like, generally regularly curved but sometimes almost hooked distally; inner edges smooth with one distinct but generally 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 generally slightly more curved than left. Thorax: pronotum sellate, clearly narrower than head, generally with a slight notch in anterior margin and entire posterior margin. 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 posterior half of abdomen. Arrangement of enteric valve cushions showing trilateral symmetry: the odd cushions are on average 18% longer than the even cushions, generally without any hump or with humps weakly developed, however, the pilosity becoming abruptly very dense shows the place where a hump is expected ( Fig. 41); secondary cushions wide at the upstream end narrowing noticeably downstream with a homogeneous spine scattering. Caecum always rather small, best seen in ventral view, near centre of abdomen, lobed (two to five small lobes).

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 3–7 spines on carina and 0–2 on ventral side; fore trochanter with 5–7 spines or strong setae; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of 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 4; Figs 30, 41). Size: the workers of I. finitimus are, on average, medium sized in the genus Isognathotermes (but with large overlapping on several other species: Fig. 30). Head capsule weakly sclerotised (except mandibles). Antennae 14.5 articles, rarely 14. 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 64–74% 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 very high density of rather short bristles on a globular bulge ( Fig. 41); supporting bristles are generally numerous: 22–29 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 (two to five small lobes, sometimes only sketched).

Chorology-ecology

The geographic distribution of I. finitimus is linked with the continental forests of central Africa; it includes the central and northeastern Congolian lowland forest and the Victoria Basin forest-savanna mosaic ecoregions ( Fig. 38).

Molecular data

Seven mitogenomes of I. finitimus are published alongside this work (GenBank accessions: see Supp. file 3 and ‘Material examined’). They are characterized by less than 1.05% dissimilarity with each other (Supp. file 4), with the sample DJ 0741 being the most dissimilar. Phylogenetic reconstructions based on full mitogenomes placed them in a sister relationship to the species I. ugandensis and I. minitabundus , to which they exhibit less than 2% dissimilarity.

Remarks

In the absence of genetic information, I. finitimus is often difficult to ascertain as its morphology places it in the middle of the genus Isognathotermes ; for the species with a finitimus EVA alone, there are partial overlaps with I. bulbifrons and I. planifrons , and also with I. phallicaecalis sp. nov., and I. phalloides sp. nov. but these last two are distinguished by their caecum.

Integrative taxonomy comes into its own here: in particular, chorology is a valuable aid: two samples – DJ 0655 and DJ 0656 – collected at Yangambi (Tshopo Province, DRC), were initially identified as I. gibbifrons on the basis of their morphology (although in disagreement with the chorology of this species). Mitogenome-based phylogenetic reconstructions subsequently placed these samples in I. finitimus .