Field Evaluation and Behavioral Response of Black Earwig, Chelisoches morio (Fabricius) (Dermaptera: Chelisochidae) to the Coconut Leaf Beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae)

Abstract

INTRODUCTION

This study was conducted to know the behavioural response of the predator to its prey. The study included an assessment of the different ways the predator captures its prey, which gender was more productive in eating the prey, its speed of eating the prey. This study was done to reduce the damage of the prey to the coconut trees through field evaluation.

METHODS

Two experiments were conducted. The laboratory experimentation includes the observation of the predator's way of capturing the prey, which gender was more productive in eating the prey, and speed of eating the prey. Also, the field evaluation was used to reduce the damage of the prey that infested coconut trees.

RESULTS

In the laboratory experimentation, the female predator had an average time of 31.75 minutes while the male predator had an average time of 64.88 minutes —the male predator located and captured CLB longer than its female counterpart in both trials. Only about 22.22% of the males were able to capture and preyed upon CLB, the other 77.78% moved back and forth and sometimes towards the prey. However, more females (60%) spent lesser time capturing CLB than males. In the control treatment, from an initial damage rating two, which corresponds to about 21% to 40% damage, this was increased to about 41% to 60%. In the treatment with predator-release, damage of CLB was rated on the average 1.5, which is about 40% reduction from the initial damage. In contrast, damage in the control group was up by about 20% of the initial damage.

DISCUSSIONS

Laboratory observations showed that C. morio, mostly females, captured and preyed upon CLB larvae. Female black earwig usually uses their cerci in capturing the prey, and each antenna of the predator separates whenever they eat. Field experiments involving the release of the predator C. morio against CLB in coconut palms caused a reduction in damage by the pest by about 40%. These could impact on the recovery of CLB damaged palmsin Barangay. Bunga, Nagcarlan, Laguna with continuous release of C. morio.

In conclusion, there is a significant difference in the behavioral response of the predator to its prey. Results also show that there is a significant difference in the field evaluation of the predator to its prey. It also showed that the female predator's consumption time was shorter than male predators. Therefore, there is a significant difference between the rates of consumption of male and female predators.