Discoxenus minutus, Kanao, Taisuke & Maruyama, Munetoshi, 2015

Kanao, Taisuke & Maruyama, Munetoshi, 2015, Eight new species, a new record, and redescription of the genus Discoxenus Wasmann, 1904: The first record of termitophilous rove beetles in Cambodia (Coleoptera: Staphylinidae: Aleocharinae), Zootaxa 4044 (2), pp. 201-223 : 215-216

Discoxenus minutus n. sp.

( Figs. 11, 12 , 105–120 )

Type materials. Holotype: ♀, 500 m S of Ankor Wat, Siem Reap, Cambodia, 5 VI 2012, Maruyama M. leg. (Colony no. MMCB-T-2012-1-002).

Paratypes: Cambodia: 2♂♂, 3♀♀, same data as holotype (2♂♂, completely dissected). 2♀♀, 1 km S of Angkor Wat, Siem Reap, 18 VIII 2012, Maruyama M. leg. (Colony no. MMCB-T-2012-2-003) (1♀, abdominal segments dissected off). 1♀, North Wall of Preah Khan, Siem Reap, 19 VIII 2012, Maruyama M. leg. (Colony no. MMCB-T-2012-2-005). 1♂, 1♀, Siem Reap, Ankor Thom, Bayon, 20 VIII 2012, Maruyama M. leg. (Colony no. MMCB-T-2012-2-009). 1♂, 1♀, 1 km W of Banteay Prei, Siem Reap, 21 VIII 2012, Maruyama M. leg. (Colony no. MMCB-T-2012-2-0017) (1♂, completely dissected). 1♂, 1♀, 0.76 km NE of Preah Kham, Siem Reap, 18 VIII 2014, Kakizoe S. & Maruyama M. leg. (Colony no. SK002). 2♂♂, same locality data to SK002, 19 VIII 2014, Kakizoe S. leg. (Colony no. SK007).

Diagnosis. This species is distinguished from other Discoxenus species by a combination of the following four character states: macrochaetotaxy of tergites III–VIII (6, 6, 6, 6, 6, 6), sternites III–VII with macrosetae only at each posterior margin, paramere with paramerite more than 3 times wider than condylite ( Fig. 119 ), and spermatheca with basal part more than 1.5 times longer than apical part ( Fig. 120 ). This species is most similar to D. kohkongensis , but is distinguishable from it by a male aedeagal median lobe with apically rounded crest ( Fig. 118 ).

Description. Head ( Fig. 105 ) approximately 1.3 times wider than long. Antenna ( Figs. 11, 12 , 106 ) with segment I longer than other segments; segment II as long as segment III, with 3 macrosetae; segment III trapezoidal; segment IV transverse; segment V wider than other segments; segments VI–XI successively narrowed distally; segments VI–VII wider than long; segment VIII subquadrate; segments IX–X longer than wide; segment XI approximately 2.5 times longer than wide, widest at middle. Labrum ( Fig. 107 , left side) with anterior margin slightly concave at middle; median projection of apodeme short, with apex broadly rounded; 5 lateral setae present in ventral view ( Fig. 107 , right side). Mandibles ( Figs. 108, 109 ) covered with approximately 30 pores. Left mandible ( Fig. 108 ) with adoral margin moderately pointed at apical third. Right mandible ( Fig. 109 ) with a distinct tooth. Maxillary palpal segment III approximately two times longer than wide. Mentum ( Fig. 110 ) approximately 2.3 times wider than long, covered with around 40 pores. Labium with prementum covered with 12– 14 pores.

Pronotum ( Fig. 111 ) sparsely covered with approximately 44 macrosetae, 6 minute setae present around anterior margin. Elytron ( Fig. 112 ) transverse, sparsely covered with several setae at anterolateral outer corner, 12 macrosetae present on disc. Metaventrite approximately 1.3 times as long as mesoventrite.

Tergites III–IV ( Fig. 11 ) almost without seta. Tergites V–VII with a row of setae anteapically. Tergite VIII ( Fig. 113 ) with posterior margin pointed, 3 pairs of macrosetae present at posterior margin, with 2 pairs of macrosetae around middle. Macrochaetotaxy of abdominal tergites III–VIII = 6, 6, 6, 6, 6, 6. Sternite III ( Fig. 12 ) with posterior half densely covered with setae. Sternites IV–VIII with a row of yellow setae at middle. Sternites III–VII with 6–10 macrosetae at posterior margin.

Male. Sternite VIII ( Fig. 114 ) with 3 pairs of macrosetae at posterior margin, 2 pairs of macrosetae present at middle. Median lobe of aedeagus moderately narrowed toward apical lobe in ventral view ( Fig. 117 ); basal capsule with distal crest rounded apically in lateral view ( Fig. 118 ); apical lobe less than half as wide as basal capsule in lateral view ( Fig. 118 ). Paramere ( Fig. 119 ) with paramerite more than 3 times wider than condylite; velar sac sclerite with 5–6 setae; apical lobe with 4 minute setae at apex.

Female. Sternite VIII ( Fig. 115 ) with 2 pairs of macrosetae at posterior margin and middle, respectively. Spermatheca ( Fig. 120 ) with basal part approximately 1.8 times longer than apical part.

Measurement. Body length = average 1.62 mm (1.53–1.73 mm, N = 10), pronotal length = average 0.54 mm (0.51–0.56 mm, N = 10), pronotal width = average 0.73 mm (0.68–0.77 mm, N = 10), elytral length = average 0.38 mm (0.36–0.39 mm, N = 10), elytral width = average 0.41 mm (0.39–0.43 mm, N = 10).

Etymology. The specific epithet minutus is a Latin adjective meaning “small,” in reference to the small body size of this species.

Host species. Hypotermes makhamensis Ahmad, 1965 and H. cf. xenotermitis ( Wasmann, 1896) .

Comments. Total of 13 specimens of D. minutus were collected and morphologically observed in the present study. Six beetle specimens were collected from only one colony (Colony no. MMCB-T-2012-1-002) of H. cf. xenotermitis . The other seven beetle specimens were found in four different nests of H. makhamensis . All specimens of D. minutus were directly collected from the fungus gardens of their host termites, and it is unlikely that the beetles may have accidentally intruded in the nest of one of these host species.

There are small morphological differences between the specimens collected from the nests of H. makhamensis and H. cf. xenotermitinis. The specimens collected from H. makhamensis nests have slightly narrower elytra and broader paramerites of paramere than those of the specimens collected from H. cf. xenotermitinis nests. However, given the present data, we consider these differences to be insufficient for a species-level distinction. Examination of further material and DNA analysis will provide more data for species delimitation.

Figures

FIGURES 5 – 12. Habitus. 5 – 6. Discoxenus phourini n. sp.: 5. Dorsal view, 6. Ventral view. 7 – 8. D. kohkongensis n. sp.: 7. Dorsal view, 8. Ventral view. 9 – 10. D. hirsutus n. sp.: 9. Dorsal view, 10. Ventral view. 11 – 12. D. minutus n. sp.: 11. Dorsal view, 12. Ventral view.

FIGURES 105 – 120. Discoxenus minutus n. sp.: 105. Head, 106. Antenna, 107. Labrum (left side = dorsal view, right side = ventral view), 108. Mandible, left, 109. Mandible, right, 110. Mentum, 111. Pronotum, 112. Elytron, right, 113. Tergite VIII, 114. Sternite VIII, male, 115. Sternite VIII, female, 116. Tergites IX and X, 117. Median lobe of aedeagus, ventral view, 118. Median lobe of aedeagus, lateral view, 119. Paramere, 120. Spermatheca.