Cannibalistic behavior of biological control agent Oenopia conglobata (Linnaeus, 1758) (Coleoptera: Coccinellidae) under laboratory conditions

Abstract

Abstract Background Oenopia conglobata (Linnaeus) (Coleoptera: Coccinellidae) is a generalist predator feeding on several insect pests and utilized as a biological control agent in Türkiye. However, significant cannibalism has been observed among its different life stages under low food/prey availability. This study determined adult-egg, adult-larva, larva-egg, and larva-larva cannibalism of O. conglobata under laboratory conditions. Results Cannibalism among different life stages was observed under no supplemental diet (treatment group) or sufficient (100 Ephestia kuehniella eggs per individual) supplemental diet (control group). Fifty eggs per adult were provided to the 24 h-starved male and female adults for determining adult-egg cannibalism. Similarly, male, and female adults received 30 and 20 1st and 2nd instars, respectively to observe adult-larval cannibalism. Likewise, 10, 20, 30 and 40 eggs to 24-h starved 1st, 2nd, 3rd, and 4th instars, respectively were provided to record larval–egg cannibalism. By the same way, 12-h starved 4th instar was provided 1st instar (20 per individual) to determine larval–larval cannibalism. The experiments for males, females, and instars were conducted separately and cannibalism was assessed by prey consumption in treatment group relevant to the control group. Cannibalism significantly differed among sexes and instars (for larva-egg cannibalism). Overall, males and females consumed higher number of eggs in treatment group compared to their relevant controls. Female and male adults in treatment group exhibited 8.27- and 7.16-fold cannibalism on eggs. Likewise, females exhibited the highest cannibalism (2.84-folds) on 1st instar. The 4th instar consumed the highest number of eggs; however, the highest cannibalism rate was recorded for the 3rd instar. The 3rd instar exhibited 4.63-fold cannibalism on eggs. Nevertheless, the 4th instar exhibited 3.56-folds cannibalism on 1st instar. Conclusions Starved O. conglobata individuals exhibited significant cannibalism among different life stages. Therefore, during mass rearing they shouldn’t be starved. Furthermore, the cannibalistic behavior should be considered during the mass release of O. conglobata.