A study on the abundance of egg production by Epilachna chrysomellina Fabricius (Coccinellidae: Coleoptera) and its relation with temperature and relative humidity.

摘要

Epilachna chrysomellina Fabricius, order Coleopera, family Coccinellinae, is one of the phytophagous insects that feed on cucurbitacae plants. It is one of the insects that has economic effects and belongs to the genus Epilachna. It is a multi-habitat insect, distributed throughout the world. It is found in the southern region and the western coastal area of the Kingdom of Saudi Arabia due to the abundance of cucurbit plants. The insect passes through all four developmental stages, and changes in temperature and relative humidity (RH) affect its biological behavior mainly its reproduction and development. The insect are abundant in numbers during certain months of the year due to the favorable conditions of temperature and RH especially March, February and January, and the egg production is lowered gradually in April and May, and no egg production was noticed in June due to the gradual increase in temperature and reduction in RH. The favorable temperature and RH ranges for egg production were recorded between 23-38 degrees C and 30-75% RH respectively. The insect show a peculiar pattern of its life cycle with atmospheric variations. The female insect lays its eggs in blocks on the lower surface of the plant leaf, with average number of eggs reaching 27.8 eggs, which hatches during 17.14 days and larval average age is 8.2 days and the pupa takes 6 days to change into adult.