FUNCTIONAL RESPONSE OF MENOCHILUS SEXMACULATUS F. (COLEOPTERA: COCCINELLIDAE) TO DIFFERENT DENSITIES OF

Abstract

The research work was conducted in the laboratory of the Department of Entomology, Hajee Mohammad Danesh Science and Technology University, (HSTU), Dinajpur during October 2016 to March 2017. The functional response of Menochilus sexmaculatus (Coleoptera: Coccinellidae) to five densities of Aphis craccivora Koch (Homoptera: Aphididae) nymphs hosted on broad bean (Lablab purpureus Linn.) was investigated in the laboratory conditions. The research work was carried out on leaf petiole in petri dishes with 10 replications. A linear relationship between the rate of consumption and prey density was observed with r 2 values between 0.72 and 0.96. Plotting prey density against prey killed by four larval instars, and adult males and females of M. sexmaculatus fit well with the type II Holling’s model. The rate of searching efficiency and handling time were estimated as 0.58 d -1 and 0.0629 day for first instar, 0.75 d-1 and 0.061 day for second instar, 1.03 d-1 and 0.029 day for third instar, 1.03 d-1 and 0.0127 day for fourth instar, 1.19 d-1and 0.0163 day for adult male, 1.08 d-1and 0.007 day for adult female, respectively. Thus, handling time decreased from first instar to female. The most effective stages for prey of M. sexmaculatus were females, fourth instar, and males. The functional response data, the model predicts a maximum number of 142.85, 78.74, 61.43, 34.13, 16.23 and 15.89 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. Adult females consumed the highest number of prey, followed by fourth instars and adult males. The voracity of larval stages, adult male and female of M. sexmaculatus were estimated as 11.13, 12.332, 21.182, 32.51, 27.82 and 35.87 (aphids/d), respectively.