Quantitative measurement of leaf area consumption by Epilachna vigintioctopunctata (Fabricius) (Coleoptera : Coccinellidae) using image processing

Abstract

The leaf area of a solanaceous weed, Solanum carolinense, consumed by larvae and adults of a leaf scraping coccinellid beetle, Epilachna vigintioctopunctata, was measured using a computer-assisted image processing system (IPS). The accuracy of this IPS was examined by measuring areas of 25 mm×25 mm, 50 mm×50 mm, and 100 mm×100 mm reference plates. The relative measurement error of the IPS was <1% for all plates. It was also demonstrated that the IPS could be effectively used to measure the leaf area consumed by a leafscraper insect by comparing the IPS measurements with those of an area meter. A feeding experiment of E. vigintioctopunctata on S. carolinense was carried out for 38 days at 25°C under 16L-8D, and the leaf area consumed was measured by the IPS. An average beetle consumed 1, 429.5±131.6 (S. D. ) mm2 of leaves to complete its larval development and consumed 2, 510.9±306.2 mm2 of leaves during the first 10 days of its adult stage.