Friend or foe? Revealing the omnivorous feeding behavior of the ring-legged earwig on brassicas

The predatory ring-legged earwig, Euborellia annulipes (Lucas, 1847) (Dermaptera: Anisolabididae), exhibits omnivorous feeding habits, enabling it to incorporate non-prey items into its diet. This behavior is thought to offer additional needed benefits from the occasional consumption of plant material. This study examined the hypothesis that herbivory of E. annulipes on various species of cultivated Brassica has a positive effect on its biological traits and is influenced by the availability of essential food sources. The provisioned plant material (pieces of leaf) consisted of the following Brassica species: pak choi cabbage, Portuguese cabbage, cabbage, and radish did not improve the biological performance of the earwig when compared to a diet without plant material. Nevertheless, 66.0% of the second instar nymphs developed successfully when fed only pak choi cabbage, and 43.3% did so when fed solely on Portuguese cabbage. Herbivory by E. annulipes on brassicas occurred in the presence and absence of a diet, although it was significantly more pronounced when no other food sources were available. Among the four Brassica species studied, pak choi cabbage exhibited the highest feeding frequency and consumption rate. Additionally, pak choi cabbage grown under controlled conditions and exposed to routine releases of earwigs showed no reduction in productivity. These findings indicate that E. annulipes can consume brassica leaves, demonstrating species-specific variations in this consumption. However, conditions of food scarcity lead to increased consumption of plant material, while repeated releases of earwigs do not affect the growth and yield of pak choi cabbage plants.