Plotinini Miyatake, 1994

Tribe Plotinini Miyatake, 1994 View in CoL

Diagnosis. Body small to medium-sized, moderately to strongly convex, glabrous or almost glabrous with very short to suberect, sparse pubescence. Antennae with 10 antennomeres ( Fig. 1a, b View FIGURE 1 ), with four terminal antennomeres forming antennal club. Terminal maxillary palpomere securiform, apically strongly transverse ( Fig. 1c View FIGURE 1 ) or, rarely, weakly dilated apically. Labium with mentum subtrapezoidal, palpomeres moderately slender, apical palpomere being acuminate-cylindrical ( Fig. 1e View FIGURE 1 ), distance between labial palps about twice as broad as width of basal palpomere. Mandibles robust, with a subapical tooth just behind apical tooth ( Fig. 1d View FIGURE 1 ), incisor edge and molar tooth well developed. Prosternum “T” shaped, with anterior margin variable from straight to produced forming a chin piece, partially or nearly fully covering mouthparts and antennae when head is retracted ( Fig. 1f View FIGURE 1 ). Elytra with punctation distinctly dual, often with a row of coarse punctures near suture, rarely punctation almost uniform. Prothoracic hypomera with or without distinct anterolateral foveae ( Fig. 1f View FIGURE 1 ). Tarsi four-segmented, tarsal claws simple, slightly thickened basally ( Fig. 1h View FIGURE 1 ). Abdominal postcoxal lines usually complete, if incomplete with an additional oblique lateral line. Male genitalia with penis guide shorter than parameres, subtriangular in shape in inner view, with welldeveloped parameres; penis slender, strongly curved. Female genitalia with coxites elongate triangular; spermatheca lacking a well-differentiated nodulus and ramus, infundibulum present or absent.

Distribution. South and southeast Asia (recorded from India, China, Vietnam, Laos, Thailand, Malaysia, Indonesia, Japan).

Notes. The generic classification of Plotinini needs a reexamination based on morphological and molecular evidence because genera like Ballida Mulsant and Buprestodera are likely to be synonyms. At least two species of Indian Plotinini , Buprestodera inornata Miyatake and Protoplotina ambigua Poorani , appear to show extreme to moderate variations in the shape, extent of completeness, and symmetry of the abdominal postcoxal lines. As stated by Poorani et al. (2021) in the case of P. ambigua , it is highly unusual because the shape and extent of abdominal postcoxal lines in Coccinellidae are usually constant within a species though occasionally variations are found between the sexes. In most available works on Plotinini , few specimens only have been studied and it remains to be seen if this is a common feature across the tribe. Miyatake (1994) used incomplete abdominal postcoxal lines with an associate line as a diagnostic character for Protoplotina in his key to genera of Plotinini . In view of the documented variations, the generic definitions and keys based on abdominal postcoxal lines need to be modified wherever applicable.

Immature stages. Immature stages ( Fig. 2 View FIGURE 2 ) are known only for Protoplotina ambigua ( Poorani et al. 2021) . Eggs ( Fig. 2a, b View FIGURE 2 ) are laid either singly or in small groups of 2–3 on the same substrate occupied by the host and are elongate oval, pearly white to pale yellow with a distinctly sculptured chorion ( Fig. 2b View FIGURE 2 ). The larva ( Fig. 2c, d View FIGURE 2 ) is elongate, fusiform and yellowish with short, reddish-brown spines sparsely distributed on the dorsal surface and much longer, elongate setae on the lateral sides. Pupation takes place on the leaves or other substrates on which the mealybug host is present. The pupa ( Fig. 2e, f View FIGURE 2 ) is of pale creamy-yellowish colour and densely setose with reddish-brown setae on the dorsal and lateral sides.

Biology. Little information is available on the prey associations of Plotinini . Protoplotina spp. are known to be associated with Aphidoidea s.l. ( Poorani 2003), mealybugs, diaspine scales, and whiteflies on various host plants ( Poorani et al. 2021). Host plant and prey associations are well documented only for P. ambigua ( Poorani et al. 2021) . Omkar & Pervez (2004) listed whiteflies and scale insects as the prey of Buprestodera and Paraplotina , supposedly based on Miyatake (1969), but no specific information on the host associations of Plotinini is provided in Miyatake (1994).

Genera recorded from India. Three genera, namely, Buprestodera , Paraplotina , and Protoplotina , are currently known from this region. In this study, we report a fourth genus, Plotina , for the first time, from Meghalaya, northeastern India. Plotinini are rarely collected and poorly represented in institutional collections in India.