LIFE CYCLE OF LADYBIRD BEETLE (Rodolia sp.) AND ITS PREDATION EFFICIENCY ON MANGO MEALYBUG ( Drosicha mangiferae)

Abstract

The life cycle and predation efficiency of ladybird beetle(Rodolia sp.) on mango mealybug (Drosicamangiferae ) were studied under the central laboratory of the Department of Entomology, Sher-e-Bangla Agricultural University, Dhaka, during December, 2015 to March 2016. Initially the eggs were deep yellow to pale red in color. The average length and breadth of the eggs were 1.21±0.07 mm and 0.67±0.09 mm, respectively. The eggs hatched within 12 to 14 days with an average of 12.90±0.57 days. The larvae were soft bodied, reddish in color, elongate and passed through four larval instars in three moults. The duration of larval period was 64.00±19.80 days. The 1st, 2nd, 3rd and 4th larval instars lasted for 8, 17, 22 and 31 days, respectively. The final instar larvae attained a greater size and become more strong and stout. Their body sizes was9.55±0.39 mm in length and 3.02±0.05 mm in breadth. The duration of the 4th instar larvae varied from 17 days to 31 days. The duration of pre-pupal and pupal stage varied from 2 to 5 days and 3 to 8 days respectively. The total duration from egg to adult was completed within 67 to 105 days. The adult beetle was initially orange in color but finally it gained red color. The size ranged from 7.00 mm to 8.40 mm in length and 5.00 mm to 5.50 mm in breadth. Ladybird beetle fed on mango mealybug. But their rate of feeding varied. They feed in both day and night but mainly in day time. The feeding rates increased gradually from the 1st instar to 2nd instar but decreased sharply in the 3rd instar and in the adult stage as well. One 1st instar larva of ladybird beetle consumed 0.63±0.13 1st instar nymph per day. Second instar larva of ladybird beetle fed 0.92±0.27 nymph of 2nd instar per day. The average consumption of 3rd instar ladybird beetle larva was 0.52±0.05 nymph of 3rd instar per day and an adult ladybird beetle fed 0.13±0.08 adult mango mealybug per day.