Protoplotina ambigua Poorani, sp. n.

Figs. 1–5

Diagnosis: Protoplotina ambigua sp. n. (Figs. 2–4) is externally similar to P. vietnamica Miyatake in having a transverse median macula on each elytron but it is much darker and does not have a curved row of punctures on either side of the suture as in the latter. The coloration is variable and some specimens are pale brown with a pair of narrow, transverse, yellow elytral spots about middle that are often united to form a single elytral band across middle (Fig. 2a). The other known Indian species, P. nigrosuturalis Poorani, can be distinguished from P. ambigua sp. n. by the pale yellow coloration, presence of a sutural black stripe and the shape of postcoxal lines. The male (Figs. 5 i–k) and female genitalia, particularly spermatheca (Fig. 5l), of P. ambigua sp. n. are also diagnostic.

Description: Male: Length: 0.85–1.24 mm; width: 0.62–0.85 mm; TL/TW: 1.37–1.50; PL/PW: 0.34–0.51; EL/ EW: 0.98–1.20. Form (Figs. 2–4) elongate oval, broadest around middle of elytra; dorsum apparently glabrous, but head and pronotum with distinct, short, procumbent setae directed forwards, elytra with much shorter, erect hairs sparsely distributed on discal area and lateral margins (Figs. 2 a–d), hairs on lateral margins more clearly apparent than those on discal area, elytral apices with distinctly more conspicuous and denser pubescence comprising short, semi-erect / adpressed hairs. Head and pronotum yellowish to testaceous; elytra dark brown, each elytron with an ill-defined, dull reddish median macula (Figs. 2c, d); occasionally elytra paler brown with a pair of transverse, narrow, yellowish bands across middle (Figs. 2b, 3 a–d), these bands sometimes medially joined to form a single stripe (Fig. 2a) or often much reduced and narrow, not touching either suture or lateral margin, basal and lateral margins also paler yellowish in such examples (Figs. 3 a–d). Ventral side yellow or yellowish brown or dark brown except legs, antennae, maxillae and mouthparts lighter, yellowish. Head (Fig. 5a) with distinct, reticulate-striate sculpture, punctures shallowly impressed, separated by 2–4 diameters; eyes coarsely facetted, ocular margins apically divergent; frons broad with widely separated eyes, head 3.62–4.30× as wide as each eye, interocular distance 1.90–2.38× as wide as each eye.

Pronotum with lateral borders almost straight except anterolateral corners broadly rounded, posterolateral corners obtusely angulate, lateral sides finely margined with a distinct gutter, basal margin bordered. Disc of pronotum densely punctate, punctures separated by 1–3 diameters, basal margin with finer punctures, interspaces smooth smooth. Prosternum (Figs. 4b, c) anteriorly produced and distinctly bordered, covering antenna and mouthparts, its anterior margin medially somewhat truncate to broadly rounded; punctures on prosternum distinct, coarse, closely spaced in middle, basal margin with much smaller punctures.

Scutellar shield small, elongate triangular. Elytral lateral borders finely margined with a gutter and with very short, but distinct hairs; elytral base with more regular punctation, punctures clearly dual only in discal area, larger punctures irregularly intermixed with fine punctures, in some areas widely separated and closer elsewhere; punctation distinctly finer towards elytral apices and not clearly dual as on discal area, interspaces between punctures smooth and shiny. Mesoventrite basally barely emarginate. Mesoventral postcoxal lines rounded and laterally complete (Fig. 4b). Metaventrite with coarse but widely separated punctures and a distinct discrimen.

Abdominal postcoxal lines extremely variable, distinctly angular and complete (Figs. 4b, 5g) or incomplete, running parallel to posterior margin of ventrite 1 with an associate line (Figs. 5b, d–f), associate line shows the following variations: occasionally shorter and apically slightly curved inwards (Figs. 5b, e) (or) short and straight, not approaching the lateral line (Fig. 5d) (or) longer and straight, closely approaching but not touching the lateral line (Fig. 5f); rarely postcoxal line on either side of the abdomen differently shaped (Fig. 5h). Last abdominal ventrite arcuate in female (Fig. 5c), more widely and shallowly arcuate in male (Fig. 5b).

All femora distinctly enlarged and swollen (Fig. 4b), tarsal claws almost simple with a basal dilation.

Male genitalia (Figs 5 i–k) as illustrated, penis guide much shorter than and not reaching beyond midlength of parameres in ventral view (Fig. 5i), broadest basally, progressively narrowed to a truncate apex; inner and outer margins and apices of parameres (Fig. 5j) densely setose; penis elongate, strongly curved, with a well–developed penis capsule, outer arm of capsule reduced, inner arm not so well developed, broad and short but distinct, penis apex distinctly narrowed and produced (Fig. 5k).

Female: Externally similar to male. Female genitalia (Fig. 5l) as illustrated, coxites elongate triangular, spermatheca lacking a well-defined nodulus and ramus, with a rod-like infundibulum.

Material examined: Holotype, male: “ INDIA: Tamil Nadu: Podavur: NRCB research farm, N10°47’20.16” E078°34’30.40”, VI-VII.2020, Ex. Jack Beardsley mealybug infested stem of guava, R. Thanigairaj” (NBAIR). Paratypes: 7 males and 3 females, with the same data as holotype (4: NBAIR, 3: NPC, 3: UASB). Other material: Many specimens with same data except date of collection VI–VIII.2020.

Etymology: The specific epithet is an adjective of Latin origin and is in reference to the extremely variable nature of the abdominal postcoxal lines in this species.

Distribution: India: Tamil Nadu.

Notes: Miyatake (1994) used incomplete abdominal postcoxal line with an associate line as a diagnostic character for Protoplotina in his key to the Asiatic genera of Plotinini, but P. ambigua sp. n. has extremely variable abdominal postcoxal lines ranging from complete to incomplete with an associate line. It is highly unusual in Coccinellidae because the shape and extent of abdominal postcoxal lines are usually constant within a species though occasionally slight variations are found between the sexes. In view of this, the generic definition of Protoplotina needs to be modified.

Biology / Hosts: All the life stages of P. ambigua sp. n. were collected in association with Jack Beardsley mealybug, Pseudococcus jackbeardsleyi Gimpel & Miller (Hemiptera: Sternorrhyncha: Pseudococcidae) infesting guava. The Jack Beardsley mealybug is a recently introduced alien invasive pest in India. It is of Neotropical origin and infests several host plants including banana, guava, etc. The larvae and adults of P. ambigua sp. n. have a cryptic habit and are always hidden in crevices and other concealed niches under the bark. Eggs (Figs. 1a, b) are laid either singly or in small groups of 2–3 on the same substrate occupied by the host mealybug and are elongate oval, pearly white to pale yellow with a distinctly sculptured chorion (Fig. 1b). The larva (Figs. 1c, d) is elongate, fusiform and yellowish with short, reddish brown spines sparsely distributed on the dorsal surface and much longer, elongate hairs on the lateral sides. Pupation takes place on the leaves or other substrates on which the mealybug host is present. The pupa (Figs. 1e, f) is pale creamy yellowish and densely setose with reddish brown hairs on the dorsal and lateral sides.

Infestation by other mealybugs such as Ferrisia virgata (Cockerell) and the Asian guava whitefly, Aleuroclava psidii (Singh) (Hemiptera: Aleyrodidae) was observed on the guava plants on which the specimens of P. ambigua sp. n. were collected. But all the immature stages of P. ambigua sp. n. were invariably collected in association with the colonies of P. jackbeardsleyi and it appears to be the most likely host insect. Few adults were also collected on the bark of Phyllanthus emblica (L.) (Euphorbiaceae) infested by unidentified mealybugs and diaspine scales. Mealybugs are added as new hosts for Protoplotina as the other two Indian species, P. nigrosuturalis and Protoplotina nr. vietnamica Miyatake have been recorded as feeding on Aphidoidea s. l. (Poorani 2003).

Barcode sequence: A 697-bp barcode sequence of Protoplotina ambigua sp. n. is available under the accession number MW 326876 in GenBank.