Schedorhinotermes rectangularis Ahmad, 1965

Takematsu, Yoko & Vongkaluang, Charunee, 2012, A taxonomic review of the Rhinotermitidae (Isoptera) of Thailand, Journal of Natural History 46 (17 - 18), pp. 1079-1109 : 1103-1106

Schedorhinotermes rectangularis Ahmad, 1965

( Figures 12A–J , 14F )

Schedorhinotermes rectangularis Ahmad, 1965: 27–29 , figs.21–22.

Material examined

THAILAND: Nakhorn Ratchasima: three series, Khao Yai National Park , 700 m alt., 4 March 1998, Y. Takematsu coll. ; Chanthaburi: Chanthaburi , 26 March 1965, M. Ahmad coll. [BMNH] .

Diagnosis

Major soldier. Small species. Head rectangular, almost parallel-sided, without hairs on head capsule and pronotum. Eyes present, but small and whitish. Inner edge of apical tooth of left mandible not convex; the basal part of the right mandible without a distinct step. Antennae with 16–17 segments.

Minor soldier. Small species. Head widest at posterolateral end of antennal sockets and slightly narrowed posteriorly, with four hairs on head capsule. Eyes present, oval, but whitish and faint. Apical tooth long and strongly incurved, DAM1 / DM1M2 1.33–1.47 (1.40). Antennae with 15–16 segments. Postmentum arched, with a faint projection at anterior one third in lateral view.

Measurements (mm)

Major soldier. Six soldiers from three series: HL, 1.36–1.54 (1.49); mHW, 1.16–1.31 (1.27); LML, 0.88–0.94 (0.91); PL, 0.40–0.45 (0.43); PW, 0.71–0.84 (0.78); PosL, 0.94–1.14 (1.07); PosW, 0.44–0.46 (0.45).

Minor soldier. 12 soldiers from three series: HL 0.72–0.82 (0.79); mHW, 0.64–0.74 (0.70); LML, 0.58–0.64 (0.61); PL, 0.31–0.38 (0.34); PW, 0.46–0.56 (0.52); PosL, 0.48–0.55 (0.52); PosW, 0.27–0.31 (0.29) .

Distribution

Thailand (Northeast, East).

Remarks

This species is similar to S. medioobscurus in size. Ahmad distinguished this species from S. medioobscurus by their head shapes and the number of antennal segments. In the major soldier, S. rectangularis has a relatively rectangular head compared with S. medioobscurus , but the ranges of head length / width index of both species are almost overlapping. These two species could not be separated clearly by this character. However, this species is easily distinguished from S. medioobscurus by the other characters as follows; no hair on head capsule and pronotum; inner edge of apical tooth of left mandible not convex; apical teeth short; posterior part of marginal teeth of right mandible not swollen. In the minor soldier, it is difficult to separate these species. The number of antennal segments which Ahmad used to distinguish both species is variable within a colony. Ahmad also distinguished S. rectangularis from S. medioobscurus by lateral side of head capsule not being concave. But this character state is so faint that it is difficult to recognize. From my careful observations, S. rectangularis has only two pairs of long bristles on the head capsule ( S. medioobscurus has more than three pairs), although there are some exceptional individuals. It also distinguished by having longer apical teeth. The postmentum of S. rectangularis has a small projection on the anterior third in lateral view, but S. medioobscurus does not.

Distributions of Rhinotermitidae in Thailand

Species distribution maps are shown in Figures 13 and 14 .

There has been general agreement that the biogeographic transition between the Sundaic fauna (Peninsular Malaysia, Sumatra, Borneo, Java and associated islands) and the continental Indomalayan fauna occurs on the Thai / Malaysian peninsula. Hypotheses as to the exact location of the biological boundary vary from the northern end of the peninsular (around 14 ◦ N) to the Kra Isthmus (around 10 ◦ N), which is the narrowest land bridge connecting Peninsula Malaysia to the continental part of Asia ( Wallace 1869; Walls 1976; Hughes et al. 2003; Woodruff 2003). The Kra Isthmus is located between two of our sampling sites: Namtok Huai Yang National Park (Prachuap Khiri Khan Prov., figs. 1–18) and Khao Pla Teao Wildlife Conservation (Surat Thani Prov., figs. 1–20).

Taking account of the biogeographical boundary, termites in Thailand show three distinct distribution patterns: (1) species that occur in Thailand’s continental land area, (2) species that occur only in Thailand’s peninsula, and (3) species that occur throughout the country, in both the peninsula and the continental area. The 11 species that have been recorded in this survey can be grouped in the following way. Three species have a continental distribution; Reticulitermes assamensis , Schedorhinotermes rectangularis and Prorhinotermes flavus . Prorhinotermes flavus is usually found in coastal forests and mangroves, and has a wide distributional range from India to Indonesia. Although there is only one record in North Thailand, it is possible that this species also occurs along parts of Thailand’s coastline. The record of Reticulitermes in Central Thailand is one of the southernmost records in the Indomalayan region for this genus. This genus is restricted to the Continental part of Thailand. Four species are restricted to the peninsula; Coptotermes premrasmii , Coptotermes kalshoveni , Parrhinotermes microdentiformisoides and Parrhinotermes buttelreepeni . The northernmost distribution of this group was that of Parrhinotermes microdentiformisoides ( Figure 14B ), which was far south of the Kra Isthmus. Four species are found throughout Thailand; Coptotermes curvignathus , Coptotermes gestroi , Schedorhinotermes malaccensis and Schedorhinotermes medioobscurus .

Figures

Figure 12. Soldier of Schedorhinotermes rectangularis Ahmad.(A) Head of major soldier, dorsal view; (B) head of major soldier, lateral view; (C) pronotum of major soldier; (D) postmentum of major soldier; (E) mandibles of major soldier; (F) head of minor soldier, dorsal view; (G) head of minor soldier, lateral view; (H) pronotum of minor soldier; (I) postmentum of minor soldier; (J) mandibles of minor soldier. Scale bar 0.5 mm.

Figure 13. Distribution of Coptotermes and Reticulitermes in Thailand. (A) Coptotermes curvignathus; (B) Coptotermes gestroi; (C) Coptotermes kalshoveni; (D) Coptotermes premrasmii; (E) Reticulitermes assamensis. (Record of C. premrasmii is from original description.)

Figure 14. Distribution of Parrhinotermes, Prorhinotermes and Schedorhinotermes in Thailand. (A) Parrhinotermes buttelreepeni; (B) Parrhinotermes microdentiformisoides; (C) Prorhinotermes flavus; (D) Schedorhinotermes malaccensis; (E) Schedorhinotermes medioobscurus; (F) Schedorhinotermes rectangularis.