Lepidotrigona amruthae Viraktamath and Rojeet, 2022

Viraktamath, Shashidhar & Thangjam, Rojeet, 2022, Description of four new species of Lepidotrigona (Hymenoptera: Apidae: Meliponini) from north-east India, Zootaxa 5175 (1), pp. 1-30 : 12-13

Lepidotrigona amruthae Viraktamath and Rojeet sp. n.

( Figs. 4c , 5c , 6e , 10 , 11 , 12 )

Diagnosis. Lepidotrigona amruthae is a member of the ventralis species group with male and female bees measuring a mean of 5.08 and 4.09 mm in body length and 4.39 and 4.24 mm in forewing length, respectively. The male bees are distinct in having the apical margin of metasomal sternum 4 produced into a small lobe and sinuate laterally ( Fig 12 a ); the apicosubmedian lobes of sternum 5 widely separated (0.29 mm) ( Fig. 12 b ); apicomedian lobe long (0.33 mm) and acutely pointed in the sternum 6; apodemal lobes moderately separated from each other ( Fig. 12 c ) and longer penis valve (0.87 mm) and gonostylus (0.86 mm) ( Table 2 ).

Female bees are smaller (4.09 mm body length); mesoscutum bordered with short, yellow, plumose, scale-like hairs; first metasomal tergum with the distinct light brown, narrow semi-circular band and malar space length very short (0.10 mm).

Description

Males

Coloration. Head, mesosoma, metasoma black ( Fig. 10 a ); labrum, scape dark reddish-brown except the basal bulb light reddish-brown; pedicel, flagellomeres dark reddish-brown on both upper and lower side; ocelli transparent, pale to dark reddish-brown, raised above the level of vertex integument; compound eyes reddish-brown ( Fig. 10 c ); Mesoscutum with three, very narrow, shiny longitudinal stripes extending up to the middle of mesoscutum; tegulae dark reddish-brown ( Fig. 10 b ); wings with brownish tinge; pterostigma, veins light brown. Legs reddish-brown except for the terminal four tarsal segments ochraceous. Metasomal tergum 1 pale with a dark brown, broad semi-circular band; remaining terga black except the terminal tergum yellowish-brown; sterna pale with dark brown bands of various size and shape across each tergum giving a banded appearance ( Fig. 10 a, b ).

Pilosity. Entire face, clypeus clothed with plumose white hairs ( Fig. 10 c ); vertex, upper region of occiput with long pale hairs; lower occipital area with a patch of white fine hairs; genal, post-genal margins fringed with pale long hairs ( Fig. 10 a ). Mesoscutum not bordered with scale-like hairs, but margins fringed with fine, short pale-yellow hairs; mesoscutellum fringed with long pale-yellow hairs ( Fig. 10 b ). Pronotal lobe, mesepisternum, metepisternum, anterolateral areas of propodeum with white thick plumose hairs ( Fig. 10 a ). Anterior and posterior margins, upper surface of the hind tibia with short white hairs. Metasomal terga with white fine hairs, density increasing towards terminal segments; sterna with fine, dense white hairs with higher density towards medial and terminal ends.

Morphometry. Males measure 5.08, 1.78 and 1.20 mm in body length, head width and head length, respectively ( Table 1 ); eye 1.13 mm long, 0.49 mm wide; upper interocular distance 2.76× and 5.25× greater than interocellar (0.38 mm) and ocellocular distance (0.20 mm), respectively; median ocellus 4.75× larger than the malar space length (0.04 mm); scape 0.50 mm long, 0.14 mm wide; forewing 4.39 mm long, 1.46 mm wide; wing diagonal length 1.27 mm; hind tibia 2.34× longer than the hind basitarsus (0.62 mm) while 1.41× wider than hind basitarsus (0.37 mm).

The ratio of head length to width 0.67; eye length to upper interocular distance 1.08; interocellar to ocellocular distance 1.90; forewing length to width 3.01; hind tibial length to forewing diagonal length 1.14; hind basitarsus width to hind tibial width 0.73 ( Table 3 ).

Metasomal sterna and genitalia. The following description is based on the dissection of five males. Sternum 4 is less sclerotized with gradulus not touching the antecosta; apical margin distinctly produced into a small, broad lobe medially; sinuate on both lateral sides ( Fig. 12 a ). Gradulus of sternum 5 touches antecosta for short distance medially; apicosubmedian lobes slender, 0.30 mm long, pointed terminating into 2 to 4 short spines; both lobes separated by 0.29 mm broad inverted U-shaped concavity; each apicolateral lobe as long as wide (0.10 mm) with rounded apex ( Fig. 12 b ). Antecosta of sternum 6 weakly convex medially; the apicomedial lobe 0.33 mm long, acutely pointed at apex. Apodemal lobes moderately separated from each other ( Fig. 12 c ).

Genitalia asymmetrical except gonostyli, well sclerotized ( Fig. 12 d ). The left gonocoxa larger, 0.23 mm long, 0.51 mm wide while the right gonocoxa smaller measuring 0.23 and 0.44 mm in length and width, respectively. Penis valve 0.87 mm long with a basal width of 0.35 mm at the base; terminal half of each penis valve curved differently, often in the same direction, overlapping with each other, terminating in slender pointed apices ( Fig. 12 d ). Gonostylus arising laterally at the base of each gonocoxa, tubular, sclerotized only at basal 1/4 th, 0.86 mm long with a width of 0.03, 0.06 and 0.07 mm at the base, middle and terminal parts, respectively; sinuate at about mid-region, terminal half of each gonostylus expanded and medial and lateral surfaces lined with series of long and short setae, density increasing towards apex ( Fig. 12 e ).

Females

Coloration. Head, mesosoma black ( Fig. 11 a ); scape dark reddish-black except for the basal bulb lighter; pedicel, flagellar segments dark reddish-brown; ocelli transparent pale in colour; compound eyes dark reddishbrown to black ( Fig. 11 c ). Legs dark reddish-brown; tegulae black; wings blackish brown; pterostigma, veins dark brown. Mesoscutum with three very narrow, shiny longitudinal stripes arising from the anteromedial margin, extending up to the middle of mesoscutum. Metasomal tergum 1 pale with a narrow, light brown semi-circular band; remaining terga with various shades of brown with intersegmental lines dark brown thus appearing banded ( Fig. 11 a, b ); Some bees (30%) have terga black except the terminal segments light brown to ochraceous; sterna ochraceous.

Pilosity. Clypeus, entire face clothed with dense, white plumose hairs ( Fig. 11 c ); vertex, upper occiput with grey erect hairs, the lower part of occiput with fine white hairs ( Fig. 11 a ). Mesoscutum surrounded by yellow scale-like hairs; mesoscutellar margin fringed with ochraceous hairs ( Fig. 11 b ); pronotal lobe, mesepisternum, metepisternum, anterolateral areas of propodeum clothed with plumose yellowish hairs ( Fig. 11 a ); anterior, posterior margins of the hind tibia with ochraceous mixed with dark brown setae. Metasomal terga and sterna with fine white hairs, the density increasing progressively towards terminal segments.

Morphometry. Females measure a mean of 4.09 mm in length and 1.77 mm in head width; head length 1.26 mm; eye 2.95× longer than its width (0.38 mm); upper interocular distance 3.34× and 4.18× greater than interocellar (0.35 mm) and ocellocular distance (0.28 mm), respectively; median ocellar diameter 0.15 mm; malar space length 0.10 mm; scape 6.50× longer than its width (0.10 mm); forewing 4.24 mm long, 1.47 mm wide; wing diagonal length 1.23 mm; hind tibia 2.16× longer than hind basitarsus (0.68 mm).

The ratio of head length to width 0.71; interocellar to ocellocular distance 1.25; scape length to eye length 0.58; forewing length to width 2.89; hind tibial length to head width 0.70; hind tibial length to forewing diagonal 1.18; hind basitarsus to hind tibial width 0.75 ( Table 3 ).

Nest: A colony was found nesting in a tree. The entrance tube was soft, 5.3 cm long with a funnel-like opening of 2.00 cm diameter. The entrance tube was protruding from the nest, dark brown at the base and lighter towards the anterior portion ( Fig. 6 e ).

Material examined. Holotype: Male: Mizoram: Thenzawl (23.2808° N, 92.7741° E, Altitude 783 m a.s.l.), 12. x. 2020, leg. Rojeet T. deposited at UASB . Paratypes: 10 males, 28 females with the same collection data deposited at UASB ; one female paratype will be deposited at ZSIK .

Etymology. The species name is derived based on the Sanskrit word “Amrutha” meaning “nectar of immortality”. The name refers to the high medicinal value of the honey produced by stingless bees.

Figures

FIGURE 4. Comparison of metasomal sterna 4 (s-4), 5 (s-5) and 6 (s-6) of Lepidotrigona thenzawlensis (a), L. rajithae (b), L. amruthae (c) and L. sikkimensis (d) (Not to scale)

FIGURE 5. Comparison of genitalia dorsal view (1), seen from above (2), terminal expanded part of gonostylus (3) of Lepidotrigona thenzawlensis (a), L. rajithae (b), L. amruthae (c) and L. sikkimensis (d) (Not to scale)

FIGURE 6. Nest entrance and brood chamber of Lepidotrigona thenzawlensis(a, b), L. rajithae (c, d) and nest entrance of L. amruthae (e)

FIGURE 10. Lepidotrigona amruthae n. sp. Male holotype: a. lateral habitus, b. head, mesosoma and basal part of metasoma dorsal view, c. head frontal view

FIGURE 11. Lepidotrigona amruthae n. sp. Female paratype: a. lateral habitus, b. head, mesosoma and basal part of metasoma dorsal view, c. head frontal view

FIGURE 12. Lepidotrigona amruthae n. sp. Male paratype: a. Metasomal sternum 4, b. sternum 5, c. sternum 6, d. genitalia, e. gonostylus terminal part