Insects, being among the most diverse and abundant organisms in terrestrial ecosystems, are inevitably exposed to ubiquitous micro- and nanoplastic contaminants. Although studies on the impact of these contaminants on terrestrial insects are gradually emerging, they remain limited in scope. In this study, we investigated the biological traits (including foraging behavior, food assumption, digging ability, body weight and survival) of the Japanese carpenter ant, Camponotus japonicus, in response to exposure to polystyrene micro- and nanoplastic (PS-M/NP) solutions containing three particle sizes (0.05, 1 and 50 μm) and four concentrations (0.1, 1, 10 and 50 mg/mL). The results showed that worker ants exhibited significant foraging preference and food consumption for non-contaminated solutions in multiple-choice experiments, indicating that worker ants C. japonicus can differentiate and avoid feeding on PS-M/NP-contaminated solutions. Meanwhile, PS-M/NPs significantly reduced the foraging ability of worker ants in multiple-choice and no-choice experiments, with the smallest particle size (0.05 μm) and highest concentration (50 mg/mL) of PS-M/NPs resulting in the longest pre-foraging period, the lowest percentage of licking and the amount of food consumption. In addition, the weight of sand removed by worker ants, the body weight and survival of worker ants showed a dramatic decline with a decrease in particle size, increase in concentration and prolonged in exposure time of PS-M/NP-contaminated solutions. The results of this study confirm that PS-M/NPs have an adverse effect on these worker ants in a particle size, concentration and exposure time-dependent manner, with small particle size, high concentration and longer exposure time being the key factors in decreasing the foraging behavior and biological traits of this insect.

The gregarious ectoparasitic beetle Dastarcus helophoroides (Fairmaire) is considered a primary biocontrol agent for controlling several cerambycid pests in East Asian countries. A thorough study of reproductive behavior is a prerequisite for the mass production of natural insect predators. Nonetheless, little attention has been given to this ectoparasitic beetle. We performed a series of trials to assess whether the adult copulation duration, a key behavioral trait, is differentially influenced by physiological and ecological factors, including body size, mating history, kinship, sex ratio, mating sequence, feeding status, ambient temperature, photoperiod, and time of day. Additionally, the effect of the copulation duration on the reproductive output of this beetle was also investigated. The results indicated that the copulation duration varied considerably, ranging from 1.12 min to 16.40 min and lasting for an average of 9.11 ± 0.12 min. Females with longer copulations laid more eggs and had a greater proportion of eggs hatched. Medium-sized individuals copulated significantly longer than small- and large-sized individuals. The copulation durations were significantly longer when both sexes experienced an asymmetric mating history than when both sexes experienced a symmetric mating history. Inbred couples copulated significantly longer than outbred couples. In terms of the adult sex ratio, increasing the density of females (polygamous group) or males (polyandrous group) led to significantly longer copulation durations than those in the monogamous group. The copulation durations gradually decreased with increasing the mating sequence and temperature. Food-absence couples copulated significantly longer than food-presence couples. The mean copulation duration of the scotophase was significantly longer than that of the photophase. These results demonstrate that all of the analyzed factors emerge as important factors influencing the copulation duration, ultimately affecting the reproductive outputs in this ectoparasitic beetle.