Parasitic behavior and functional responses of Chelonus formosanus (Hymenoptera: Braconidae)

Chelonus formosanus Sonan (Braconidae) serves as an important egg-larval parasitoid of lepidopteran pests across multiple families. A deep understanding of parasitic function of C. formosanus will help to explore its potential for controlling pests.

This study investigated the parasitic behavior of C. formosanus on Spodoptera litura eggs and evaluated its functional response to eggs of S. litura and Spodoptera frugiperda.

The observed parasitic behavior of C. formosanus comprised six distinct steps: searching, detecting, cleaning, probing, ovipositing, and post-oviposition cleaning. The mean duration was 186.1 min per egg mass. C. formosanus exhibited a Holling type Ⅱ functional response model to the eggs of both pest species, with parasitism rates reaching a plateau at densities of up to 250 eggs. The functional response parameters indicated a high instantaneous attack rate (α = 1.1846 vs. 1.1855 for S. litura and S. frugiperda, respectively), high maximum parasitism efficiency (Na(max): 538.45 and 564.52, respectively), and short handling time (T_h: 0.0019 and 0.0018, respectively) under experimental conditions.

These findings demonstrate the remarkable biocontrol potential of C. formosanus against both noctuid pests, providing critical theoretical foundations for mass rearing programs and integrated pest management strategies.