Micraspis tenuilinea (Walker)

POORANI, J., 2023, An illustrated guide to lady beetles (Coleoptera: Coccinellidae) of the Indian Subcontinent. Part 1. Tribe Coccinellini, Zootaxa 5332 (1), pp. 1-307 : 185-189

Micraspis tenuilinea (Walker)

( Figs 132 , 133 )

Coccinella tenuilinea Walker, 1859: 219 (Lectotype female: BMNH; Type locality: ‘Ceylon’).

Micraspis tenuilinea: Poorani et al. 2023: 458 .

Diagnosis: Length: 2.70–3.40 mm; width: 2.30–3.00 mm. Form ( Fig. 132a–d ) broad oval to circular, dorsum convex and glabrous except head with silvery white pubescence around clypeal area. Ground colour orange-yellow to reddish; head with a black transverse macula in posterior half, genae usually dark brown to black, occasionally paler; pronotum with a pair of triangular black maculae on posterior margin on either side of scutellar shield and a pair of circular discal black spots around middle; scutellar shield yellowish and bordered black, rarely fully darker; elytra orange-yellow with a black stripe on suture slightly broader in the middle, basal margin narrowly black, lateral margins of elytra very narrowly black for up to 3/4 th of its length, apical fourth yellowish.

Micraspis tenuilinea co-exists with M. discolor in peninsular India. It has a more circular, broader body outline with distinctly rounded elytra compared to M. discolor which has an oval, more elongate form with somewhat narrower elytra. Besides, the pronotum in M. tenuilinea has the basal pair of black maculae distinctly triangular in form, less oblique and irregular than in M. discolor , with two circular discal black spots located above ( Fig. 132a, b ). These pronotal spots may be often enlarged and coalesced or obsolete and sometimes only paler, reddish-brown markings are seen ( Fig. 132c ), even so, the range of colour patterns in M. tenuilinea is still noticeably different from that of M. discolor . The sutural black stripe is usually wider and more prominent in M. tenuilinea than in M. discolor . The male genitalia ( Fig. 132j–m ) and female genitalia are different from those of M. discolor as follows: apex of penis guide narrower in ventral view ( Fig. 132k ) and laterally more strongly curved in lateral view ( Fig. 132j ) than in M. discolor ; spermatheca ( Fig. 132i ) with poorly differentiated nodulus and ramus and a distinct but similarly shaped infundibulum.

Immature stages. Life stages ( Fig. 133a–m ) as illustrated, immature stages very similar to those of M. discolor .

Distribution. India (Andhra Pradesh, Karnataka, Kerala, Pondicherry, Tamil Nadu); Sri Lanka.

Prey / associated habitat. It is found in huge numbers during the panicle initiation or flowering stage of the rice crop in South India and it continues to be present even after harvest in the stubbles (unpublished data). Also collected on sugarcane at flowering stage and in association with aphid, Melanaphis sacchari Zehntner.

Natural enemy. Homalotylus sp. ( Fig. 133n ) is a common larval parasitoid of M. tenuilinea .

Notes. In South India, Micraspis tenuilinea is more common and numerically abundant than M. discolor , its better known ‘cousin’. It significantly outnumbers M. discolor in Tamil Nadu conditions by a ratio of at least 7:1 or much greater. The voluminous literature available on the biology, hosts and behaviour of ‘ M. discolor’ from India is certainly based on more than one species and most of the papers from southern India are likely to be based on M. tenuilinea as it is more abundant by severalfold ( Poorani et al. 2023).

Figures

FIGURE 132. Micraspis tenuilinea (Walker): a–c. adult, dorsal view; d. adult, frontal view; e. adult, lateral view; f. adult, ventral view; g. prosternal process; h. abdominal postcoxal line; i. spermatheca; j–m. male genitalia: j. tegmen, lateral view; k. tegmen, ventral view; l. penis; m. penis apex.

FIGURE 133. Micraspis tenuilinea (Walker), life stages: a, eggs; b–i. larva; j, k. pupa; l, m. adult; n. Homalotylus sp., its larval parasitoid.