Aethina Erichson, 1843

Dasgupta, Jhikmik & Pal, Tarun Kumar, 2022, On Aethina Erichson of Northeast India (Coleoptera: Nitidulidae: Nitidulinae), Zootaxa 5124 (5), pp. 533-550 : 535-538

Genus Aethina Erichson, 1843

Aethina Erichson, 1843: 306 . Type species: Aethina pubescens Erichson, 1843 (by monotypy)

Aethinopa Reitter, 1875: 109 . Type species: Aethinopa fulvovestita Reitter, 1875 . (Synonymised by Kirejtshuk 1986)

Pseudomystrops Grouvelle, 1913b: 389 . Type species: Idaethina humeralis Grouvelle, 1890 . (Synonymised by Kirejtshuk 1986)

Meligethopsis Rebmann, 1944: 25 . Type species: Meligethopsis singularis Rebmann, 1944 . (Synonymised by Kirejtshuk 1986)

Characterisation. General appearance ( Figs.1–18 ): Oval, rather convex dorsally and subdepressed ventrally, length 1.4 to 3.4 mm, moderately shiny, punctate-pubescent, elytral punctation often arranged in longitudinal rows, with linear rows of moderately long, decumbent setae, colour range: yellowish- or reddish-brown to chocolate brown, antenna with a compact three-segmented club, pronotum and elytra feebly explanate laterally; abdominal segments, except the pygidium, covered by elytra dorsally.

Head ( Fig. 1 ) transverse, distinctly narrower than prothorax, mandibles partly exposed, fronto-clypeal suture absent; eyes moderately large and slightly projecting, coarsely facetted; tempora well-developed, sloping posterad; slightly marked neck constriction. Tentorium with two long tentorial arms and a transverse corpotentorium present near middle. Antenna slightly longer than head; antennal insertions partially hidden under projections of frons, scape broadly elongate, segment 2 short, segment 3 and 4 narrower than segment 2; segments 5 to 8 short, subequal, about as broad as long; club 3-segmented, slightly longer than broad, segments compactly arranged. Ventrally antennal grooves narrow, extending backward subparallely. Mandible ( Fig. 10 ) broadly elongate, depression on dorsal face forming distinct mandibular cavity, tip of mandibles somewhat acute with a single apical tooth and a small tooth beneath apical tooth, mola well-developed, prostheca setose. Maxilla ( Fig. 11 ) devoid of galea; lacinia broadly elongate, apex rounded, apex and inner margin densely hairy; palpi with palpomere 1 short, palpomeres 2 and 3 subequal and transverse; palpomere 4 (apical palpomere) longer than preceding segments and fusiform, sparsely setose. Labium ( Fig. 12 ) with mentum distinctly transverse, large pits on surface, apical margin deeply emarginate; ligula transverse, with lateral lobes projecting and wing-like; palpi with palpomere 1 short, palpomere 2 transverse, palpomere 3 longest and fusiform. Labrum ( Fig. 13 ) transverse, apically bilobed, apical margin deeply incised medially; two types of dense setae: shorter setae laterally, longer and stouter setae medially.

Prothorax ( Fig. 2 ) transverse, about as broad as or slightly broader than elytra; anterior margin somewhat emarginated, posterior margin subtruncate or feebly bisinuate; anterior and posterior angles devoid of any denticle; lateral margin bordered and often arcuate; pronotal disc rather convex; prosternal process projecting behind postcoxal process, apex bulbous, slightly narrower between coxae; front coxae narrowly separated; coxal cavities distinctly transverse, externally and internally closed, trochantins exposed; notosternal sutures divergent anteriorly and extending to posterior third of lateral margin.

Meso-metathorax ( Fig. 3 ): Mesoventral process narrower than prosternal process, subcarinate. Mesocoxae moderately widely separated internally, bordered by coxal lines, lines reaching beyond middle of the distance along metaventral-metanepisternal suture, forming distinct axillary space; mesoventral process contacting metaventral process between mesocoxae almost in a straight line. Metaventrite somewhat transverse, discrimen extending upto two-thirds of metaventrite from basal margin, metacoxae as widely separated as mesocoxae (external separation), basal margin usually straight, sometimes feebly emarginate. Metendosternite ( Fig. 8 ) well developed, with a broad basal stalk bifurcated into two lateral arms, anterior tendons rather short.

Elytra and hind wings: Elytra ( Fig. 6 ) broadly elongate, sides arcuate, margined, apex conjointly or separately rounded or obliquely truncate, punctation round and distinct, often arranged in longitudinal rows; moderately long and decumbent setae; epipleura moderately developed and extending almost to two-thirds of the length from base. Hind wing ( Fig. 9 ) simple and venation reduced, with moderately long radial vein, cubitus vein not branched, anal veins absent; no subcubital fleck.

Legs ( Fig. 7 ) moderately long, trochanters short and simple, femora broadened medially; slender tibiae slightly broadened at apex with distinct apical spurs; tibiae longitudinally canaliculated, inner edge crenulated; tarsal formula 5-5- 5 in both sexes, tarsomeres 1 to 3 densely setose, slightly dilated apically, tarsomere 4 shortest; claws simple, toothed at base or medially forked.

Abdomen ( Fig. 5 ) slightly longer than broad; ventrite 1 and 5 subequal in length, with closed, semicircular coxal lines, intercoxal process moderately broad and its apical margin truncate; ventrites 2–4 short and subequal, ventrite 5 longer than each of the preceding three ventrites. Pygidium fully or partially exposed, prebasal undulate margin ( Fig. 25 ), apical margin somewhat rounded in females, truncate or forked in males with apex of anal sclerite (tergite VIII) often exposed dorsally.

Genitalia: Aedeagus ( Figs. 16–18 , 26, 28–33, 38–39 ) with sclerotised, broadly elongate median lobe having projecting apex; a single median strut running along ventral face; tegmen spatula-shaped, forming a broadly elongate envelope, with tapered or rounded apex, parameres fused and setose in the apical half of the lateral margin, lateral edges subparallel or tapering towards apex; tegminal struts join basally to form a single strut around median lobe. Anal sclerite and spiculum gastrale as in Fig. 14 . Ovipositor ( Figs. 15 , 27 ) with well-developed paraprocts, valvifers, long and slender coxites, distinctly forked in cases [subgenus Idaethina ], and short styli attached laterally near the apices of the coxites.

Sexual Dimorphism: Distinct dimorphism with males possessing an additional anal sclerite, sometimes visible below pygidium.

Habitat: Most species inhabit subcorticolous niche of tree trunks of fallen logs, and flowers; exhibit mycetophagy, anthophagy or phyllophagy in larval or adult stages; breed in stores of pollen, seed capsules of some plants and apiaries.

Distribution: Occur in tropical and subtropical parts of both Eastern and Western hemispheres but more prevalently in the Eastern hemisphere. Indo-Malayan sub region of the Oriental Region bears a sizeable number of species. Invasive nature of species like Aethina tumida (minor bee pest) has resulted in its spread to many areas outside tropics and subtropics. About 14 species are known from India, of which seven species have been recorded from its northeastern zone only (see Map 1 ).

List of species of Aethina from Northeast India

1. Aethina (Aethina) argus Grouvelle, 1890

2. Aethina (Aethina) cyaneipennis Grouvelle, 1903

3. Aethina (Aethina) inconspicua Nakane, 1967

4. Aethina (Aethina) vicina Grouvelle, 1894

5. Aethina (Circopes) subquadrata ( Motschulsky, 1858)

6. Aethina (Idaethina) subrugosa (Grouvelle, 1894)

7. Aethina (Idaethina) orientalis ( Nietner, 1856)

Key to the subgenera and species of Aethina of Northeast India

1. Body usually densely pubescent, femoral lines of abdominal ventrite I usually slightly deviating from hind coxae and form a small axillary space before the middle of ventrite I...........................................................2.

- Body not sparsely pubescent, femoral lines on abdominal ventrite I form acute angle near the hind coxae above middle of ventrite I........................................................ Aethina (Idaethina) Gemminger et Harold …6.

2. Body more subdepressed and less convex, elytra with diffused pubescence, apex of prosternal process distinctly flattened, about as broad as or broader than antennal club.................................................... Aethina (s. str.)...3.

- Body rather convex, elytra with longitudinal rows of longer setae interspersed with rows of shorter setae, apex of prosternal process not distinctly flattened and narrower than antennal club. Body reddish-brown, densely pubescent. Male genitalia with spoon-shaped tegmen having rounded apex, median lobe with pointed apex ( Figs. 26, 28–29 )................................................................................... Aethina (Circopes) subquadrata ( Motschulsky, 1858)

3. Elytra metallic blue, antennal club subconical........................... Aethina (s. str.) cyaneipennis Grouvelle, 1903

- Elytra reddish brown to blackish, antennal club longer than broad...............................................4.

4. Body reddish-brown, with ten black spots- four on pronotum, five on elytra and one on the last segment of abdomen ( Fig. 40 ), dorsum covered by dense, recumbent yellowish grey pubescence, which is black on the spots. Male genitalia ( Figs. 41, 42 ) with elongated tegmen, somewhat tongue-shaped with a median oval depression near apex and median lobe bud-like with rounded apex................................................................. Aethina (Aethina) argus Grouvelle, 1890

- Body devoid of any black spots..........................................................................5.

5. Body brown to almost black; anterior margin of head, mouthparts, sides of the pronotum, scutellum, and part of elytra often paler. Cuticle covered with long, reddish, quite contrasting hairs, interspersed with darker hairs. Male genitalia with tegmen longer than broad, with apex rounded ( Fig. 48 ) or apex truncated ( Fig. 44 ); median lobe subrectangular in shape with a slightly protruding apex ( Figs. 45–47 )........................................ Aethina (Aethina) inconspicua Nakane, 1967

- Body uniformly dark brown to blackish. Cuticle covered with moderately long, golden, semi-erect setae. Male genitalia with spoon-shaped tegmen having truncate apex and elongated median lobe with pointed apex ( Figs. 30–31 )..................................................................................... Aethina (Aethina) vicina Grouvelle, 1894

6. Body colour usually black, elytra often slightly paler; apex of pygidium truncate; elytral punctation shallow and indistinct. Male genitalia with elongated tegmen having sub-parallel lateral sides and rounded apex, and elongated median lobe with nipple-shaped apex ( Fig. 18 )......................................... Aethina (Idaethina) orientalis ( Nietner, 1856)

- Body colour usually reddish brown, elytra not paler; apex of pygidium slightly excised; elytral punctation rather deep and distinct, oval in shape. Male genitalia with trowel-shaped tegmen having rounded apex, and hexagonal median lobe with apex slightly bulging ( Figs. 16–17 )..................................... Aethina (Idaethina) subrugosa (Grouvelle, 1894)

Figures

MAP 1: Distribution of Aethina in Northeast India.

FIGURES 1–9. Aethina (Idaethina) subrugosa (Grouvelle, 1894), line drawings: 1, head, dorsal view; 2, prothorax, ventral view; 3, meso-metathorax, ventral view; 4, mesoscutellum, dorsal view; 5, abdomen, ventral view; 6, right elytron, dorsal view; 7, front leg; 8, metendosternite; 9, hind wing.

FIGURES 10–18. 10–17: Aethina (Idaethina) subrugosa (Grouvelle, 1894), line drawings: 10, mandible, dorsal view; 11, maxilla, ventral view; 12, labium, ventral view; 13, labrum, dorsal view; 14, anal sclerite (tergite VIII) and spiculum gastrale; 15, ovipositor; 16, male genitalia: tegmen, ventral view; 17, male genitalia: median lobe, ventral view; 18, Aethina (Idaethina) orientalis (Nietner, 1856) male genitalia: tegmen and median lobe.

FIGURES 25–39. Aethina (Circopes) subquadrata (Motschulsky, 1858): 25–29: 25, abdomen with pygidium, dorsal view, photograph; 26, male genitalia with tegmen and median lobe, microphotograph; 27, ovipositor, microphotograph; 28, male genitalia: tegmen, line drawing; 29, male genitalia: median lobe, line drawing; Aethina (Aethina) vicina Grouvelle, 1894: 30–31, 34–35: 30, male genitalia: tegmen, line drawing (derived from Kirejtshuk, 1986); 31, male genitalia: median lobe, line drawing (derived from Kirejtshuk, 1986); 34, dorsal habitus; 35, ventral habitus. Aethina (Aethina) nigrocastanea Grouvelle, 1903: 32–33, 36–39; 32, male genitalia: tegmen, line drawing; 33, male genitalia: median lobe, line drawing; 36, ventral habitus, photograph; 37, dorsal habitus; 38, male genitalia: tegmen, microphotograph; 39, male genitalia: median lobe, microphotograph.

FIGURES 40–50. Aethina (Aethina) argus Grouvelle, 1890: 40, Dorsal facies, line drawing (adapted from Grouvelle, 1890); 41, Tegmen, line drawing (adapted from Kirejtshuk, 1986); 42, Median lobe, line drawing (adapted from Kirejtshuk, 1986); 43. A. (A.) cyaneipennis Grouvelle, 1903: Dorsal facies (line drawing adapted from Kirejtshuk, 1986); 44–50. A. (A.) inconspicua Nakane, 1967 (adapted from Kirejtshuk, 1986): 44, Tegmen of specimen from Punjab; 45, 47, Median lobe and 48, Tegmen of specimen from S. China; 46, Median lobe of specimen from Punjab; 49, Dorsal facies of specimen from Fuji; 50, Dorsal facies of specimen from Punjab.