Fecundity and developmental stages of Rice Blue Beetle, Leptispa pygmaea Baly (Coleoptera: Chrysomelidae) on rice varieties

摘要

Biological studies on fecundity and developmental stages of rice blue beetle, Leptispa pygmaea Baly (Coleoptera :Chrysomelidae) were conducted at the Regional Agricultural Research Station Pattambi, Kerala Agricultural University, under net house condition on two rice varieties viz., Jyothi (short duration) and Aiswarya (medium duration) during June to October 2005. Adult beetle laid oval shaped yellow eggs on both the leaf surfaces either singly or in parallel rows with an average fecundity of 16.8eggs on short duration variety Jyothi and 14.3 eggs on medium duration rice variety Aiswarya. The incubation period was 3.4 days in both varieties. The grub had five larval instars each with duration of 1-2 days and completed grub development within a mean period of 8.2 days. The grub pupated on the surface of leaf by getting attached loosely at its posterior end. The pupal period was 3.2 and 2.9 days in Jyothi and Aiswarya, respectively and completed the life cycle within 14.8 in Jyothi 13.8 days in Aiswarya. The pre-oviposition period of L. pygmaea showed no marked difference between varieties of rice. The longevity of adult varied with the sex of blue beetle. Males lived longer than females. Adult male of L. pygmaea lived for 40.9 days on Jyothi and36.7 days on Aiswarya. The male life span was longer in Jyothi than Aiswarya. The females lived for an average period of 25 days in both varieties, thus indicating a shorter life for females than males.