Isognathotermes ugandensis ( Fuller, 1923 )

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 : 144-152

Isognathotermes ugandensis ( Fuller, 1923)

Figs 26–31, 33, 65–69, distribution map: Fig. 49; Tables 16–17

Cubitermes ugandensis Fuller, 1923: 191–192 .

Cubitermes antennalis Sjöstedt, 1924c: 493 .

Mirotermes ( Cubitermes) antennalis – Emerson 1928: 513–515, text-fig. 57, pl XXXIII.

Cubitermes ugandensis – Sjöstedt 1926: 251–252, table 10 b1–b2. — Snyder 1949: 165. — Williams 1966: 107–108, figs 15, 31, 47, 64, 82. — Bouillon & Vincke 1971: 269. — Krishna et al. 2013: 1942. — Josens & Deligne 2019: 60–61 .

Cubitermes antennalis – Williams 1966: 107–108. — Krishna et al. 2013: 1943.

Cubitermes ugandensis – Hellemans et al. 2021: 233.

Isognathotermes antennalis – Hellemans et al. 2021: 233.

Isognathotermes ugandensis – Hellemans et al. 2021: 233.

With four new subspecies:

Isognathotermes ugandensis burundii Josens & Deligne subsp. nov.

Isognathotermes ugandensis kenyae Josens & Deligne subsp. nov.

Isognathotermes ugandensis malawii Josens & Deligne subsp. nov.

Isognathotermes ugandensis ugandensis Josens & Deligne subsp. nov.

Diagnosis

This species is very close to I. minitabundus and I. severus . The worker (all four subspecies) has a fungifaber EVA but in 6% of the samples examined, it has an EVA intermediate between the fungifaber and finitimus patterns. Its valve is, on average, somewhat larger than that of I. minitabundus ( Fig. 31). It is among the medium- to large-sized workers of the genus Isognathotermes ( Fig. 30). As in I. minitabundus , the premolar tooth of the left mandible is more apparent than in most other species.

The soldier (all four subspecies) is among the medium- to large-sized soldiers in the genus Isognathotermes ( Fig. 28), on average somewhat larger than I. severus . It has the left mandible slightly curved to almost straight and obviously less curved than the right mandible as in I. minitabundus but more asymmetrical than in I. severus (SMlc/SMrc = 0.68–1.02, vs 0.51–1.03 in I. minitabundus and 0.79–1.24 in I. severus ). Its head is generally clearly bulbous, but this is shared with I. severus (and also with I. bulbifrons which has a finitimus EVA ).

The imago is among the medium- to large-sized imagines of the genus Isognathotermes ( Figs 26, 65). The premolar tooth on left mandible is more apparent than in most other species (but this is shared with I. severus and I. minitabundus ).

Contrary to usual, the morphology of imagines is more heterogeneous than that of soldiers and workers ( Figs 65–69), and this heterogeneity is linked to origin and altitude ( Fig. 66), revealing clear subgroups that are hardly detectable in soldiers or workers. Pending more comprehensive molecular data (most of the available samples being too old to be sequenced), we propose to distinguish four subspecies based on overall size (first PCA factor) and eye and ocelli dimensions (second PCA factor).

Etymology

The name ugandensis (from Uganda and Latin desinence - ensis, from) clearly refers to the country ( Uganda) of the type locality.

Material examined

See hereafter the material examined of Isognathotermes ugandensis ugandensis and other subspecies.

Historical review

Fuller (1923: 191–192) described this species under the name Cubitermes ugandensis . He provided descriptions of alate, imago, and soldier.

Sjöstedt (1926: 251–252) provided a redescription of alate imago and soldier, together with figures of the soldier’s head, and a short first description of the worker. Sjöstedt (1926: 249–250) included Cubitermes ugandensis in imagines’ and soldiers’ keys of Cubitermes species and inserted it in a “ bulbifrons -Gruppe” of species with an upwards humped soldier’s frons.

Snyder (1949: 165) catalogued Cubitermes ugandensis in the sub-family Termitinae .

Williams (1966: 107–108) provided a detailed redescription of imago and soldier along with measurements and figures. He stated that the alate imago described by Fuller (1923) and Sjöstedt (1926) belonged to Ophiotermes ugandaensis .

Williams (1966: 108) considered C. ugandensis as a senior synonym of C. antennalis .

Emerson, in his unpublished “card catalog”, named six samples (from three nests) “ Cubitermes basilewskyi ” in honour of Pierre Basilewsky who collected this material in Rwanda, but it was neither described nor published (nomen nudum). Two such subsamples preserved in RMCA were examined by Williams in 1968 and considered to be Cubitermes ugandensis ; confirmed in this study as I. u. burundii.

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

Krishna et al. (2013: 1942) housed Cubitermes ugandensis 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 .

Here, we divide the species I. ugandensis into four subspecies that could later become true species. The problem at this stage of our knowledge is that molecular data is still scarce; these taxa can therefore only be recognised by the morphology of the imagines (which are missing from almost half the samples) and by their geographical origin.

Redescription

The redescription concerns the species; the distinction between subspecies is based mainly on the imagines’ sizes and origins: see diagnosis.

Imago

COLOUR. Head capsule: well sclerotised, fresh samples very dark, C6–C8 (C6–C 7 in long preserved imagines); fontanelle concolorous or almost so with head capsule. Postclypeus C5–C7 concolorous or slightly paler (one level) than head capsule. Antennae C4–C7 without any difference between proximal and distal articles. Thorax: pronotum C5–C7, as postclypeus, concolorous or slightly (one level) paler than head capsule; meso- and metanotum C5–C6, sometimes somewhat paler than pronotum. Legs C3–C5; tibia concolorous with femur or somewhat (one level) darker. Wings hyaline with brown to grey tinge (Cf2–Cf3), anterior veins darker. Abdomen: tergites C6–C7. Sternites appreciably paler in middle (C3–C4) with both sides darker (C4–C5); posterior sternites darker (C4–C5) 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 40–80×, these fine setae do not extend over the posterior margin. Legs very pilose, furnished (among numerous fine setae) with some stronger setae: 7–12 on the carina of fore coxa and 1–6 on the ventral side of fore coxa and on trochanter; tibia pilose, fore, mid, and hind tibia furnished with 15–30 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 Tables 16–17; Fig. 67). Size: the imagines of I. ugandensis are among the medium- to large-sized species of the genus Isognathotermes (as I. minitabundus ) ( Fig. 26). The imagines’ size is one of the criteria that distinguish the subspecies (see diagnosis). Head capsule: compound eyes oval; ocelli shortly to moderately oval, removed from eyes by a short distance with an eye to ocellus minimal distance index: IEyOcD/IOc d = 0.54–1.58 somewhat larger than in I. severus (0.39–1.29) and smaller than in I. minitabundus (1.10–1.70); fontanelle generally a tiny round or elongate marking. Antennae: 16 articles on alate individuals, shortened by amputation by some articles in king and queen. Labrum: cupola shaped, wider than long. Left mandible with apical tooth medium to small sized (IMlAmD = 0.19–0.27 mm: Fig. 27) and always more prominent than first marginal; marginal teeth three in number; second marginal appearing as an undulated edge, reduced but still present in worn mandibles, third marginal tooth with a blunt tip; premolar tooth generally well visible (best seen than in most other species); only the apical tooth is acute in unworn specimens; 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 2–5 and 9–12 branches, respectively. Gut not studied.

Soldier

COLOUR. Head capsule generally tending towards deep palette (Cd4–Cd6) becoming fader and somewhat darker 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 (one to two levels) which is generally the same colour as frons; in long preserved samples, this clearing tends to fade. Thorax and legs paler than head capsule (C3–C4) 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 always with 4–8 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 6) on carina and not any spine on ventral side (rarely one); 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 16; Figs 28, 67). Size: the soldiers of I. ugandensis 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 narrowing near posterior third or fourth, from antennal sockets sides converge towards bases of mandibles; posterior side regularly convex or sometimes with short straight parts. Upper profile always rather strongly concave; angle between extended mandibles and frons obtuse; frons with sketched to clear anterior hump. Gulamentum in ventral view always constricted in its posterior half, with sides of anterior part generally 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 90% of the samples examined) to convex; lobes angular, generally with fine, whitish, or translucent tips; anterior margin concave. Mandibles: sabre-like and rather clearly asymmetrical (but a little less than in I. minitabundus ), the left mandible is slightly curved 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 54–61% of head width, with straight or indented anterior margin and posterior straight margin. 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 always rather small, best seen in ventral view, near centre of abdomen, generally three-lobed. Arrangement of enteric valve cushions showing trilateral symmetry, the odd cushions being about 16% 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 3–5 spines on carina and 0–2 on ventral side; fore trochanter with 6–7 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 7–16 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 16, Figs 30, 67). Size: the workers of I. ugandensis are part of the medium to larger workers in the genus Isognathotermes (but with large overlapping on several other species: Fig. 30). Head capsule: weakly sclerotised (except mandibles). Antennae of 14 or more often 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 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 (better seen than in other species), third marginal tooth with a blunt tip; premolar tooth generally well visible (also better seen 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 sometimes 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 60–68% 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 (but in 6% of the samples examined, the EVA is intermediate between the fungifaber and finitimus patterns); 16–27 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 two short lobes.

Chorology-ecology

Isognathotermes ugandensis is the easternmost and southernmost species of the genus Isognathotermes ( Fig. 49) its geographic distribution is linked with the Victoria basin forest-savanna mosaic, the east Sudanian savanna, the central Zambezian miombo woodlands, and the northern Acacia-Commiphora bushlands and thickets ecoregions. It settles at high altitudes: Williams (1966) mentioned that all his C. ugandensis samples had been collected between 1100 and 2400 m a.s.l. Here, we confirm and extend this range to 625–2500 m with a range of four subspecies.

Molecular data

Of the four considered subspecies, only two ( I. ugandensis burundii subsp. nov., and I. u. kenyae subsp. nov.) were successfully sequenced. Six mitogenomes of I. ugandensis are published alongside this work (GenBank accessions: see Supp. file 3 and ‘Material examined’). Overall, mitogenomes exhibited less than 1.3% dissimilarity with each other (see Supp. file 4), with I. u. kenyae (DJ 0599) being the most dissimilar. Our phylogenetic reconstructions placed I. ugandensis + I. minitabundus as sister to I. finitimus ( Fig. 33; SHalrt /UFB = 99.3/93), with whom they are less than 2% dissimilar. Of note, I. ugandensis and I. minitabundus exhibit a fungifaber EVA which is distinctive from I. finitimus .

Remarks

The subdivision of I. ugandensis into four subspecies and the difficulty of incorporating I. antennalis into one of these subspecies betrays the vagueness that surrounds the Isognathotermes of East Africa. The morphological diversity of the imagines may result from genuine genetic differences, in which case the subspecies could become species, but it could also reflect phenotypic plasticity linked to altitude: only further molecular studies could resolve this question.