Functional responses of Laccotrephes griseus (Hemiptera: Nepidae) against Culex quinquefasciatus (Diptera: Culicidae) in laboratory bioassay.

ABSTRACT

Background and objectives: In integrated vector management programmes, major emphasis is given on the application of biocontrol agents. In the present study, the hemipteran water bug, Laccotrephes griseus (Hemiptera Nepidae) was evaluated to establish its functional response against the immature Culex quinquefasciatus Say in the laboratory. Methods: Adult water bugs (L. griseus) were collected from different ponds in Bankura, West Bengal, India. Predation rate was determined in semi-field conditions. Functional response, regression equation analysis and rate of predation were also determined in the presence of an alternative prey. Results: The long-term predation experiment (up to 30 days) revealed that L. griseus is a very good predator of mosquito larvae. The functional curve analysis of L. griseus exhibited a Type II functional response. Their handling times and coefficient of attack rates were 29.37 min and 2.17 respectively. Regression equations showed that consumption rate was directly proportional to prey and predator densities and inversely proportional to the search area. The selectivity index, niche width and food breadth were also determined. Interpretation and conclusion: The present study revealed that L. griseus can consume a good number of mosquito larvae in the laboratory conditions. The long-term bioassay also indicates their predatory response against mosquito larvae in the semi-field conditions. The result of selectivity index, niche width and food breadth were also highest for Cx. quinquefasciatus. In these respects, the water bugs L. griseus are indicative of their release in the aquatic habitat where Cx. quinquefasciatus is the most dominant mosquito species.