Cubitermes Wasmann, 1906

Josens, Guy & Deligne, Jean, 2019, Species groups in the genus Cubitermes (Isoptera: Termitidae) defined on the basis of enteric valve morphology, European Journal of Taxonomy 515, pp. 1-72 : 23-30

Genus Cubitermes Wasmann, 1906

Cubitermes Wasmann, 1906: 573 .

Cubitermes – Wasmann 1911: 149 (original description).— Holmgren 1910: 286 and Holmgren 1912: 107 (as a subgenus of Mirotermes ). — Emerson 1928: 506 (as a subgenus of Mirotermes ). — Snyder 1949: 155 (as a genus).— Krishna et al. 2013: 1911 (as a genus).

The genus Cubitermes is currently included in the Cubitermitinae. This subfamily, first proposed as the tribe Cubitermitini by Weidner (1956), then synonymised with the Termitinae ( Engel & Krishna 2004) , was eventually restored by Engel et al. (2009) as one of the eight subfamilies in Termitidae . The Cubitermitinae are characterised notably by the presence of a mixed segment and a blind diverticulum, or caecum, on the second paunch of the hindgut (P3) in workers, soldiers and imagines. They comprise 26 genera, among which Cubitermes is by far the richest in species. We consider here as belonging to Cubitermes all the species recorded as such in the recent Treatise of Krishna et al. (2013).

In this article the results are divided into two parts: the detailed re-description of the genus Cubitermes and the descriptions of nine groups of species based on their valve morphology.

Type species

Cubitermes bilobatus Haviland, 1898 , by original designation (type deposited in the NHMM). The original descriptions of Wasmann (1906; 1911) are very scant and have not been completed since, except for the worker caste ( Sands 1998). A more detailed description is therefore proposed here, based on both published and new data, for imagines (255 individuals), soldiers (427 individuals) and workers (421 individuals).

Imago

COLOUR.

Head capsule: Well sclerotised and generally dark, C6–C8 (however, long preserved imagines can become as clear as C4, as already mentioned by Williams 1966); fontanelle concolorous with or paler than head capsule (one to five palette levels paler); postclypeus C4–C7 frequently paler (one to two levels) than head capsule, sometimes concolorous; three muscle insertions on head capsule visible as paler areas, one on each side between ocellus and postclypeus, and a smaller one immediately in front of fontanelle, but these insertions are sometimes indistinct due to dark colour of head of imagines; antennae C4–C7 without any difference between proximal and distal articles.

Thorax: Pronotum C4–C7 more or less as postclypeus, frequently one to two levels paler than head capsule, with some still paler areas, that is a T-shaped marking centrally, one oval spot near each antero-lateral corner and two oval spots in middle near posterior margin; meso- and metanotum C4–C7,

frequently somewhat paler than pronotum; legs generally C3–C5, tibiae usually slightly (one level) darker than femora; wings hyaline with brown to grey tinge (Cf2–Cf4), anterior veins darker.

Abdomen: Tergites C5–C7; sternites appreciably paler in middle (C3–C4) with both sides darker (C4– C6); posterior sternites darker (C4–C6) than anterior.

SETATION

Head capsule: Labrum and postclypeus with a variable density of prominent setae set amongst a very variable density of shorter, finer setae of variable length: sometimes these small setae are almost lacking, sometimes they form a dense mat; 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; mesonotum and metanotum glabrous or with some fine setae, sometimes so small and thin that they cannot be seen even at a magnification of 100 ×, remaining, however, detectable through their setal sockets, visible as pale round spots.

Legs: Generally very pilose, often furnished with spines in various densities on fore coxae and trochanters; fore, mid and hind tibiae bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively (subapical spurs sometimes weakly developed).

Abdominal tergites: With many large and small setae; abdominal sternites with long setae, vertical or directed slightly forward, and many long and smaller setae directed backwards.

STRUCTURE (measurements in Table 1 )

Head capsule: Compound eyes nearly round to shortly oval; ocelli nearly round to oval, removed from eyes by a variable distance relative to their own greatest diameter. Fontanelle varies from a tiny round or elongate marking to a round, obvious, margined depression larger than one-tenth of head width.

Antennae: Generally 16 articles on alate individuals, rarely 15 (in 7% of individuals), or very rarely 17 (in 1 % of individuals), almost always shortened by amputation by at least one article in queens and kings (one exception, not shortened, on 116 individuals examined).

Labrum: Cupola-shaped, generally wider than long.

Left mandible ( Fig. 3 ): With apical tooth of variable length but always longer and 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 apical tooth is acute in unworn specimens; premolar tooth with proximal end obscured or partly 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 ( Fig. 3 ): With apical tooth of variable length but 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 eyes), straight to very weakly sellate, with anterior lobe short and very slightly elevated.

Wings: R1 fused entirely with costal margin, sclerotised; Rs simple, sclerotised; M not sclerotised with 2–7 branches near wingtip; Cu with 7–14 branches to posterior margin of wing.

Gut (only studied in some cases): enteric valve is weakly developed and hardly comparable with workers’ and soldiers’ valves; diverticulum (or caecum) is present as a small amorphous button.

Soldier

COLOUR

Head: Capsule generally tending towards deep palette (Cd3–Cd6) with a generally smooth but sometimes a more abrupt gradient from a dark frons to a paler back (e.g., Cd6–Cd4); antennae and labrum frequently paler than head capsule.

Mandibles: Dark (C6–C8) with an abrupt clearing on their bases (two palette levels) which are generally of same colour as frons.

Thorax and legs: Paler than head capsule (C3–C4).

Abdomen: Grey to red-brown owing to digestive bolus, sometimes with a yellow to reddish-brown tinge on tergites.

SETATION

Head capsule: With few scattered setae; on frons a dense bunch of hair-like setae surrounds and overhangs fontanelle; antennae with some 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 some large setae on lobes (generally <20, exceptionally up to 24). Thorax: pronotum and mesonotum with a small number (<20) of setae mainly located on rims.

Legs: Furnished with a row of spines along shaft of every tibia; fore coxae bear at least one fine seta and may or may not be furnished with some spines on carina and front surface; trochanters generally with some long, lined-up setae, sometimes with six or seven spines; fore, mid and hind tibiae bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs, respectively (latter sometimes weakly developed).

Abdominal tergites: With some large setae, mainly or only on their posterior rim; abdominal sternites with long setae, vertical or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 2 )

Head capsule: Always clearly sclerotised. Proportions: head length varies from being almost as wide as long to appreciably longer. Dorsal view: lateral sides mostly subparallel (frequently with a small narrowing near posterior third or fourth) or slightly convex, converging slightly towards anterior until antennal sockets or, rarely, towards posterior; from antennal sockets sides converge more or less clearly towards bases of mandibles; posterior side variable. In profile: upper profile straight to clearly concave; angle between extended mandibles and frons varies from almost right to obtuse; frons with or without an anterior frontal hump; profile of gulamentum variable. In ventral view: gulamentum variable, from almost rectangular to more or less constricted in its posterior half, with sides of anterior part either roundly convex or forming an acute widening or even a kind of ear on each side.

Antennae: Mostly of 14.5–15 articles, or rarely 14 (in 12% of specimens examined).

Labrum: Always more or less deeply bifurcate, varying from as long as wide to much wider, with sides varying from straight to slightly concave or lyre-shaped, rarely convex ( Fig. 9 ); tips of lobes rounded

or angular or with fine whitish or translucent tips; anterior margin concave, ranging from round to more or less V-shaped.

Mandibles: Sabre-like with variable curvatures; inner edges generally smooth (rarely finely serrated) with one distinct marginal tooth, sometimes very small, near molar tooth on each mandible; mandibles generally shorter or a little longer (rarely much longer) than head; entire surface of both mandibles generally smooth and glossy but sometimes matt due to very fine stripes mainly near tips.

Thorax: Pronotum sellate, as wide as 45–90% of head width, with an anterior margin varying from entire to distinctly notched in its middle.

Gut: Configuration as shown in Fig. 10 . Enteric valve placed on left side, more visible in ventral view, situated in second half of abdomen. Diverticulum of gut (or caecum) always rather small, more visible in ventral view, near centre of abdomen, amorphous or lobed, sometimes with a lobe expanded forward or backwards. Arrangement of enteric valve cushions variable, showing hexaradial, trilateral or bilateral symmetry or no symmetry at all.

Worker

COLOUR

Head capsule: Pale (C1–C3).

Antennae: Proximal articles pale (C2–C3), distal articles appreciably darker (C4–C5).

Thorax and legs: pale (C1–C3).

Abdomen: Grey to red-brown owing to digestive bolus.

Soldiers (counts) Code Range (Nb) Fore coxae: number of spines on carina SCx1CN 0–16 Fore coxae: number of spines on fore side SCx1SN 0–2

SETATION

Head capsule: Postclypeus and labrum with few scattered setae.

Antennae: With some prominent setae, some 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).

Thorax: With some scattered setae; legs furnished with a row of spines along shaft of each tibia; fore coxae bearing at least one fine seta and furnished or not with a small number of setae or spines on carina and anterior surface; trochanters with or without spines; fore, mid and hind tibiae bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs, respectively (latter sometimes weakly developed).

Abdominal tergites: With some scattered setae; abdominal sternites with long setae, vertical or slightly directed forward, often coloured and smaller setae directed backwards.

STRUCTURE (measurements in Table 3 )

Head capsule: Weakly sclerotised (except mandibles).

Antennae: Of 14–14.5 articles, rarely 15 (in 4% of specimens examined).

Labrum: Cupola-shaped, generally wider than long. Left mandible ( Fig. 3 ): 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 tooth faint (visible as an undulated edge and disappearing in worn mandibles), third marginal tooth 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; apicomarginal index variable.

Right mandible ( Fig. 3 ): Apical tooth well developed with a sharp tip when fresh; 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. Apico-marginal index variable.

Thorax: Pronotum sellate, as wide as 50 to 80% of head width.

Gut: Configuration of gut as shown in Fig. 10 . Enteric valve placed on left side, more visible in ventral view, situated in second half of abdomen. Diverticulum of gut (or caecum) always rather small, visible in ventral view, near centre of abdomen, amorphous or lobed, sometimes with a lobe expanded forward or backwards. Arrangement of enteric valve cushions variable, showing hexaradial, trilateral or bilateral symmetry or no symmetry at all.

Species groups based on enteric valve morphology

Following the suggestion made by Bouillon & Vincke (1971), the enteric valves in the worker and soldier castes were systematically examined with a possible outcome of creating new genera or subgenera. Obviously, the genus Cubitermes might have been divided into four clear taxa: one with “basic valves” (without any spatulae) and three taxa with “spatulated enteric valves” showing respectively two, three and six primary cushions ending in a flat structure looking like a spatula which sticks out of the valve. However, an ongoing molecular study suggests that some of these taxa would not be monophyletic. Therefore, in the prospect of a revision of the genus Cubitermes the first step proposed in this article is to introduce nine rather clear-cut species groups based on the morphology ( Fig 11 , Tables 3 and 4 ) and biometry ( Table 5 ) of their enteric valves. These groups, referred to here as ‘valve pattern groups’, or ‘valve patterns’ for short, have for now no taxonomic ranking, but their definition will enable a better recognition of species of Cubitermes : some species with different valve patterns indeed cannot be distinguished based on their external morphology alone.

Figures

Fig. 3. Imago and worker mandible terminology. Left mandible on the left side, A = apical tooth, m1 = first marginal, m2 = second marginal (reduced to a wave), m3 = third marginal, p = premolar tooth, MP = molar prominence (the molar tooth is hidden behind the molar prominence), MA = molar posterior acute apophysis. Right mandible on the right, A = apical tooth, m1 = first marginal, m2 = second marginal, M = molar tooth, MP = molar prominence.

Fig. 9. Basic shapes of the labrum in soldiers. The lobes are A. Truncated without sharp angles; B. Truncated with sharp angles; C. Short finger-like; D. Elongated finger-like; E. Convex almost lyreshaped; F. Lyre-shaped; G. Triangular. All drawings to the same scale.

Fig. 10. Gut coiling in soldiers and workers. A. Dorsal view; B. Ventral view. C = crop; D = diverticulum or caecum of the second paunch; Gz = Gizzard; M = mesenteron (dotted segment); MS = mixed segment; P1 to P5: first to fifth hind-gut segments (Holmgren 1909; Noirot 2001): P1 = ileum, P2 = enteric valve, P3 = paunch, P4 = colon, P5 = rectum. The gut is quite convoluted and some masked parts need to be described. In dorsal view, the distal end of the mesenteron (M) passes behind the upper loop of P3 to join P1 which is connected to P3 via P2; P3 turns forward, passes under the loops of M and P4 and finally turns left to join P4; P4 loops rightwards along M, then turns right and backwards behind M to join P5.

Fig. 11. Representative primary cushions of the various patterns encountered in the workers of the genus Cubitermes; WVPD = downstream bristly part; WVPM = middle spiny part; WVPS = spatula; WVPU = upstream spiny part. A. PC1 of the bilobatus valve pattern. B. PC1 of the oculatus valve pattern. C. any odd PC of the bilobatodes valve pattern. D. PC1 of the muneris valve pattern. E. PC6 and PC1 of the fungifaber valve pattern. E’. PC3 of the fungifaber valve pattern, twisted and partly seen in profile. F. PC1 of the finitimus valve pattern. F’. PC3 of the finitimus valve pattern, twisted and seen in profile. G. PC3 of the sankurensis valve pattern. H and H’. PC3 and PC4 of the oblectatus valve pattern. I. Any PC of the sulcifrons valve pattern. I’. Any PC of the sulcifrons valve pattern, twisted and seen in profile. All drawings to the same scale.

Tables

Table 1. Ranges of measurements taken of 257 Cubitermes Wasmann, 1906 imagines (only 103 individuals for the wings) in 56 taxa, including some possible synonyms and some possible new species (in alphabetical order of the “Code” column).

Imagines (counts)	Code	Range (nb)
Fore coxae: number of spines on carina	ICx1CN	0–25
Fore coxae: number of spines on fore side	ICx1SN	0–8
Imagines (raw data)	Code	Range (mm)
Eye: large diameter	IEy D	0.23–0.57
Eye: small diameter	IEy d	0.21–0.50
Eye distance from inferior head edge	IEyHdD	0.01–0.14
Eye to ocellus minimal distance	IEyOcD	0.05–0.25
Eye width (bulging)	IEyW	0.08–0.23
Head: length to fore edge of postclypeus	IHdL	0.82–1.58
Head: width across the eyes	IHdW	1.10–1.91
Mandible (left): length of apical tooth	IMlAL	0.10–0.39
Mandible (left): apical to first marginal	IMlAmD	0.10–0.33
Mandible (left): width of apical tooth	IMlAW	0.09–0.22
Mandible (left): functional length	IMlL	0.43–0.84
Mandible (left): length of molar tooth	IMlML	0.14–0.28
Mandible (left): first to third marginal	IMlmmD	0.10–0.19
Mandible (left): third marginal to molar	IMlmMD	0.06–0.13
Mandible (left): width of the first marginal	IMlmW	0.03–0.16
Mandible (left): width from molar prominence	IMlW	0.29–0.58
Mandible (right): apical to first marginal	IMrAmD	0.12–0.31
Mandible (right): first to second marginal	IMrmmD	0.07–0.13
Ocellus: large diameter	IOc D	0.11–0.27
Ocellus: small diameter	IOc d	0.07–0.18
Postclypeus: maximal length	IPcL	0.26–0.53
Postclypeus: width	IPcW	0.52–0.98
Pronotum: maximal length	IPnL	0.58–1.21
Pronotum: maximal width	IPnW	0.88–1.77
Tibia (hind): length	IT3L	1.06–2.31
Wing: length	IWgL	8.44–21.8
Wing: maximal width	IWgW	2.01–5.31
Imagines (indices)	Code	Range (ratio)
Eye elongation index	IEy D /IEy d	0.98–1.26
Eye size index	IEy D /IHdW	0.20–0.34
Eye elevation index	IEyHdD/IEy D	0.03–0.41
Eye-ocellus index	IEyOcD/IOc D	0.21–1.45
Eye prominence index	IEyW/IHdW	0.06–0.13
Mandible left apico-marginal index	IMlAmD/IMlmmD	0.83–1.94
Mandible right apico-marginal index	IMrAmD/IMrmmD	1.34–3.28
Ocellus size index	IOc D /IHdW	0.07–0.18

Table 2. Ranges of measurements taken of 427 soldiers in 73 taxa Cubitermes Wasmann? 1906, including some possible synonyms and some possible new species (in alphabetical order of the “Code” column).

Soldiers (raw data)	Code	Range (mm)
Soldiers (indices)	Code	Range (ratio)
Head upper concavity percentage	100*SHdC/SHdL	0.00–3.38
Mandible (left) curvature acceleration index	ln(SMlpR)–ln(SMldR)	0.09–3.01
Gulamentum thickness index	SGuH/SHdH	0.04–0.17
Gulamentum constriction index	SGuW/SGuw	1.12–2.20
Head elongation index	SHdL/SHdW	1.04–1.68
Labrum fork index	SLaFL/SLaL	0.20–0.73
Labrum widening index	SLaW/SLaL	0.98–3.85
Mandible bi-curvature index	SMlC/SMlc	1.12–2.45
Mandible (left) apico-marginal lesser curvature index	SMlc/SMlL	0.03–0.21
Gnatho-cephalic index	SMlL/SHdL	0.54–1.43
Mandible (left) robustness index	SMlW/SMlL	0.07–0.20
Valve: bilateral symmetry index	SVP1-Bil	0.80–1.88
Valve: PC1 pre-eminence index	SVP1-Pre	0.81–1.95
Valve: alternation index	SVP-Alt	0.82–1.75
Valve: average cushion length	SVP-AvL	0.31–0.82
Valve: odd PC elongation index	SVPOdd-Elg	4.97–15.8