The quarantine pest, Cylas formicarius, is a key pest of sweet potatoes during both production and storage, posing a major threat to food security in various countries. To investigate behavioral mechanisms, the ultrastructure of the heads of larval and adult stages was analyzed using scanning electron microscopy, with an emphasis on the sensilla of the mouthparts and antennae. The results reveal degeneration of the antennae and ocelli in larvae. The larval mouthparts are equipped with three types and six subtypes of sensilla. Both male and female adults have four types and six subtypes of sensilla on their mouthparts. Compared to larvae, the adult mouthparts display a greater diversity of sensilla types and higher numbers of sensilla basicaonica (SB), sensilla chaetica (SC), and sensilla digitiformia (SD). Adult antennae consist of a scape, a pedicel, and eight flagellomeres (F1–F8), with F8 showing sexual dimorphism. Seven types of sensilla, excluding SB and sensilla ligulate (SL), each with two subtypes, were identified on the antennae of adults of both sexes. SC, sensilla furcatea, Böhm bristles, and SL were newly observed in the antennae of C. formicarius adults. Additionally, one type and seven subtypes of sensilla on the adult antennae exhibit distinct sexual dimorphism in terms of structure or number. The relationship between the head structure and adaptability of C. formicarius was examined, and the functions of each sensilla were discussed, providing a theoretical basis for future studies on the behavior of this pest.

Carbon nanotubes are promising in agriculture for improving crop resilience and delivering agrochemicals. However, their effects on insect pests, especially chewing pests such as the fall armyworm (Spodoptera frugiperda), remain underexplored. In this study, we investigated how two types of functionalized multi-walled carbon nanotubes—hydroxylated (MWCNTs-OH) and carboxylated (MWCNTs-COOH), both obtained from Jiangsu Xianfeng Nano (Nanjing, China)—affect the pest’s development and reproduction. Using an age-stage two-sex life table approach, we fed larvae diets containing 0.04, 0.4, or 4 mg/g of these nanomaterials. Both types of MWCNTs exhibited concentration-dependent inhibitory effects. At the highest dose (4 mg/g), larval development was significantly prolonged, adult pre-oviposition periods increased, and fecundity (egg production) sharply declined, especially with MWCNTs-OH. Population growth parameters were also suppressed: net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) were reduced at 4 mg/g, particularly with MWCNTs-OH, while mean generation time (T) was extended with MWCNTs-COOH. Overall, MWCNTs-OH demonstrated a greater inhibitory impact compared to MWCNTs-COOH. These findings suggest that functionalized MWCNTs could serve as potential novel pest control agents against S. frugiperda by impeding its development and reproduction.

Cylas formicarius (Fabricius, 1798) (Coleoptera: Brentidae), the sweetpotato weevil, is an important quarantine pest in sweetpotato production. Exploring the detoxification enzyme responses of pests under pesticide stress helps to clarify the physiological mechanism of pesticide tolerance. Meanwhile, evaluating sublethal pesticide effects on population life tables is critical for revealing transgenerational ecological risks and guiding sustainable pest management. In this study, we analyzed how abamectin affected detoxification enzyme systems, fecundity, growth, and development of C. formicarius. The sweetpotato root-dipping method was used to assess the 48 h toxicity of abamectin to C. formicarius adults. The adult C. formicarius had LC₁₀ and LC₃₀ values of 0.645 and 1.709 mg/L, respectively. Sublethal abamectin induced significant temporal alterations in CarE, GST, and CYP450 activities in C. formicarius. The three detoxification enzymes exhibited distinct dynamic trends and divergent induction or inhibition responses under LC₁₀ and LC₃₀ stress, showing clear temporal specificity. The oviposition period, adult longevity, and fecundity of the parental generation were significantly reduced by sublethal abamectin. In the F₁ generation, developmental periods of eggs, larvae, and pupae were longer, whereas adult longevity and total lifespan were shorter than those of the control, and fecundity was also markedly decreased. These results demonstrate that changes in detoxification enzyme activities constitute an important physiological response of C. formicarius under abamectin stress. Population life-table analysis further confirmed the transgenerational inhibitory impacts of sublethal abamectin on weevil population performance. Combining physiological enzyme assays with population life-table evaluation helps us comprehensively understand sublethal risks of this insecticide; this work provides a theoretical basis for rational field application and long-term sustainable management of C. formicarius.