Taxonomy of the tribe epilachnini (Coleoptera: Coccinellidae) of Kerala
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Date
2020
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Department of Agricultural Entomolgy, College of Horticulture, Vellanikkara
Abstract
Coccinellidae, the lady beetle, is the largest family under the superfamily Coccinelloidea and is rich with nearly 6000 described species worldwide. Coccinellids are ecologically and morphologically diverse and exhibit a wide range of food habits spanning kingdoms and trophic levels. Majority of them are predaceous, while some are phytophagous and some mycophagous. Strictly herbivorous coccinellids are recognized under the tribe Epilachnini.Both the grubs and adults of epilachna beetles scrape the soft tissue on the surface of leaves, masticate it and suck the juice. In spite of its economic importance, no comprehensive studies have been carried out so far to explore the diversity of Epilchnini of Kerala.
The study entitled “Taxonomy of tribe Epilachnini (Coleoptera: Coccinellidae) of Kerala” was carried out inthe Department of Agricultural Entomology, College of Horticulture, Vellanikkaraduring 2018-2020 with the following objectives: (1) taxonomy of the tribe Epilachnini in different agricultural ecosystems of Kerala and (2) prepare an illustrated key for the identification of the species of Epilachnini
Purposive surveys were conducted in different districts of Kerala covering 25 locations in different agricultural ecosystems.The adults were collected by hand picking and sweeping while the immature stages viz., eggs, grubs and pupae were collected along with the associated host plants and reared to adult stage. Adults were usually collected from the upper surface of leaves whereas the immature stages from the lower surface. Wet and dry preservations were followed for temporary and permanent storage, respectively. The specimens were mounted on triangular card points and labelled with details on locality, date of collection, collector’s name and host plant. The specimens were then dried in oven at 50-60ºC for 1-2 weeks and stored for further studies.Specimens available in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara and College of Agriculture, Padannakkad were also used for the study.
The beetles were first grouped based on their host plant and elytral pattern. The specimens were then dissected and taxonomic characters viz., antenna, mouth
parts, tarsal claw, post coxal line, male and female genitalia were studied. Descriptions, illustrations and key to genera and species of Epilachnini of Kerala were prepared. The specimens were identified upto species levelbased on the available literature and taxonomic keys. Host range and distribution of species were studied and distribution map was prepared using Quantum GIS software.
The study recognized seven species belonging to four genera viz., Afidenta Dieke, Affisa Dieke,Afidentula Kapur and Henosepilachna Li. Three species under Henosepilachna were identified upto species level viz., Henosepilachnadodecastigma Wiedemann, H. septima Dieke and H. vigintioctopunctata Fabricius The species identified under Afidenta and Afidentula included Afidenta misera Weise and Afidentula bisquadripunctata. Two species studied under Affisaare A. flavicollis (Thunberg) and A. nilgirica(Weise). Afissa nilgirica was earlier described under the genus Epilachna. As per the new generic classification of Epilachnini this species belongs to Afissa and hence transferred to Afissa and this is a new combination.
Fourteen host plants were identified for Epilachnini in Kerala which included plants belonging to Fabaceae, Cucurbitaceae, Solanaceae, Poaceae and Urticaceae. Epilachna beetles exhibited oligophagy in their feeding habit, with each species showing preference to plants belonging to a particular family. Henosepilachnavigintioctopunctata always preferred solanaceous plants, whereas H. septima preferred cucurbitaceous plants. Similarly, Afidenta misera preferred plants belonging to Fabaceae and Affisanilgirica prefered members of family Urticaceae. Henosepilachnaseptima and H. vigintioctopunctatawere found to be the most widely distributed species in the study area. Apart from crop plants, some of the weeds were also reported as the host plants of epilachna beetles. This study documented the faunal composition of Epilachnini of Kerala, their host range, and geographical distribution. The information generated can be effectively utilized in planning management strategy against epilachna beetles on major crops.
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