Influence of temperature on the functional response of Anisopteromalus calandrae (Hym.: Pteromalidae) to different population densities of Callosobruchus maculatus (Col.: Bruchidae)

Abstract: Functional response is defined as the behavior of parasitoids in response to an increasing host density which is thought to be related with parasitoid success. Anisopteromalus calandrae (Howard) is a cosmopolitan solitary ectoparasitoid of immature stages of many coleopteran species, such as Callosobruchus maculatus (Fabricious). In this study the functional response of A. calandrae to different densities of 2, 4, 8, 16, 30, 40, and 50 of forth instar larvae of C. maculatus was investigated under laboratory condition of 65 ± 5% R.H., in dark condition and three different temperatures of 25, 30 and 35 °C. Various densities of host were exposed to newly emerged mated female parasitoids for 24 h. Logistic regression revealed Type II functional response for A. calandrae at all temperatures. The searching efficiencies (a) and handling times (Th) were 0.0327/h and 3.1486 h at 25 °C, 0.0531/h and 2.3546 h at 30 °C, and 0.0514/h and 2.4998 h at 35 °C, respectively. The maximum attack rates (T/Th) of parasitoids were calculated to be 7.62, 10.19 and 9.60 larvae at 25, 30, and 35 °C, respectively.These results indicate that A. calandrae is able to find and parasitize C. maculatus over a broad range of temperatures and it is probably more effective parasitoid at 30 °C.