Rhadinotermes coarctatus Sjöstedt, 1902 压缩锥形白蚁

Morphology

The description below is paraphrased from the original or a later revision, by caste; the source is cited at the end.

Diagnostic characters

Sands placed this genus in the Procornitermes branch; the soldier head capsule is sharply constricted behind the antennal sockets, similar to Fulleritermes, but it is not phylogenetically close to Leptomyxotermes/Grallatotermes, belonging instead to a mainly Neotropical clade containing Velocitermes, Tenuirostritermes and Diversitermes; the former placement in Coarctotermes was based only on soldier similarity. Soldier monotypic, the nasus conical, the mandibles with a small point, the posterior lobe usually only about a quarter wider than the anterior part, antennal segments 12; alate left mandible index 0.32–0.36, marginal tooth 2 absent, the molar plate of the right mandible with 6–7 transverse ridges diminishing towards the base, the first forming a stout tooth, the fontanelle an extremely narrow slit and hardly branching anteriorly. The genus name derives from the Greek rhadinos (tapering).

Alate

Head capsule very dark brown to pitch black, postclypeus and antennae dark sepia-brown, wings semi-transparent pale brown; the posterior margin of the head behind the compound eyes is almost semicircular; compound eyes not projecting, relatively small for the head (W/E 3.4–3.8), slightly angular-oval; ocelli small and oval, their distance from the compound eye about 1.5 times their own least diameter; postclypeus strongly inflated, 2.2 times as wide as long, the anterior margin slightly concave; antennal segments 15, segments II, IV and V nearly equal in length, II more slender, III longer. Mandibles: the apical tooth of the left mandible equal to or slightly shorter than marginal tooth 1, the distance from the apical tooth to marginal tooth 1 about one-third of the distance between marginal teeth 1 and 3 (index 0.32–0.36), marginal tooth 2 absent, the cutting edge between marginal teeth 1 and 3 entire; the apical tooth of the right mandible nearly equal to marginal tooth 1, marginal tooth 1 with a small accessory tooth near its tip; the molar plate of the right mandible weakly concave near the base of the anterior margin, the posterior margin extended into a rounded ridge, the first transverse ridge forming a stout tooth, the remaining 6–7 diminishing towards the base; fontanelle extremely narrow, slit-like, hardly branching anteriorly (more pronounced in females), slightly paler than the head to distinctly pale.

Soldier

Monotypic. Nasus conical. Mandibles vestigial, with a small point. Head capsule sharply constricted behind the antennal sockets, the posterior lobe usually only about a quarter wider than the anterior part. Antennal segments 12. Head capsule sepia-brown to pitch black, the nasus black with a reddish tip; the lateral profile of the head is raised and rounded behind the constriction and rather straight in front of it; the nasus is as long as or shorter than the rest of the head capsule measured from the posterior margin of the antennal sockets; nasus cone angle 10–20°; antennal segment II short, IV and V longer; setae confined to 4 at the nasus tip, one pair on the vertex and a few short curved hairs on the dorsal surface. 25 specimens: head length (to the nasus tip) 1.17–1.39 mm, head width 0.54–0.66 mm, hind tibia 0.92–1.10 mm.

This genus is monotypic, containing only this species; the following is the genus-level description based on the original literature; species-level measurements and intraspecific variation are given in the original.