Abstract

Studies on the biology of Selepa celtis Moore conducted at Coimbatore on Acacia nilotica ssp. Indica reveals that the insect has a fecundity of 130.2±40.4 eggs and fertility of 80.9 per cent. The incubation period is 2.5±0.5 days. The duration of first larval instar is 2.3±0.4 days, of second 2.8±0.5 days, of third 3.0±0.3 days and of the fourth larval instar is 3.4±0.5 days. The pre-pupal period is found to range between 1-2 days. The estimated pupal period is 8.9±1.2 days. The studies have brought to light that the sex ratio is skewed towards male and the adult longevity is more in the case of female. The insect has a pre-oviposition and oviposition period of 4.0±0.7 days and 2.5±0.8 days respectively. The life cycle of the insect is completed in 31.1±6.2 days. The details on the morphometry of various stages have also been brought out. Observation on feeding behaviour indicates that the first and second instar larvae of the pest feed gregariously, causing minor injury by scrapping the lower and upper surfaces of the leaflets in irregular patches and they have preference to tender leaflets. The third and fourth instar larvae feed solitarily and voraciously on both immature and mature leaflets and cause complete defoliation. They were even found feeding on the shoot tips, which indicates that the pest can considerably impair the active growth of the plants in the field condition.

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