Insects

Bacillus thuringiensis is the most extensively studied entomopathogenic bacterium worldwide; however, its sublethal effects on beetles remain poorly characterized. The aim of this study was to evaluate the toxicity of a previously selected Argentine strain of B. thuringiensis on second-instar Alphitobius diaperinus larvae during an initial 14 days of exposure, and to assess its effects at day 14 and throughout the remainder of the life cycle until death. Three treatments were applied: control, LC₃₀, and LC₅₀. Larval, pupal, and adult weight and body surface area were recorded, and nutritional composition was quantified using colorimetric methods. Insect status was monitored every 48–72 h over a total period of 540 days, until the death of the last individual. Among the evaluated variables, statistically significant differences between control and treatment groups were detected in larval area and weight, in the survival analysis and in two nutritional components: total protein and lipid content per larva. Overall, the results demonstrate that initial sublethal exposure to B. thuringiensis induces chronic lethal effects with delayed mortality in A. diaperinus, indicating irreversible physiological damage. This provides valuable information not only for understanding the biology of this insect but also for stakeholders involved in the productive scaling of beetle-targeted bioinputs.

Elateridae (Coleoptera: Elateroidea) are renowned for their clicking mechanism. However, several lineages exhibit body softening that compromises this mechanism, particularly within Plastocerini, Drilini, and Omalisinae. It remains unclear how this body softening is anatomically achieved and which specific structures are degraded in relation to the loss of clicking function. To elucidate the internal morphological adaptations and distinguish them from hard-bodied clicking elateroids, we employed micro-CT to scan Plastocerus thoracicus and reconstruct its thoracic morphology in 3D and quantified key muscle ratios (e.g., M2/M60, M4/M60). Based on our study of P. thoracicus, a detailed comparison was made with previously reported data on Campsosternus auratus (Elateridae) and Cerophytum lii (Cerophytidae). Three-dimensional reconstructions revealed significant structural divergences in P. thoracicus: (1) the clicking-related muscles M4 are markedly weaker than those in Ca. auratus and Ce. Lii. (2) the prosternal process (PP) is extremely narrow. The posterior part of the pronotum exhibits underdeveloped regions, including the posterodorsal evagination (PdE) and the posteromedial process (PmPr). (3) the mesonotum (i.e., the “biological spring” identified in previous studies) is greatly flattened and weakened. (4) the flight muscles (M60, M64) and walking muscles (M74, M75) exhibited significantly bigger volume than Ca. auratus and Ce. lii. These findings provide critical data for understanding the morphological evolution of Elateridae and offer insights into the functional adaptations of the clicking mechanism through comparative anatomy.

Mowing is a widely used agricultural management practice, yet its role in shaping plant–insect interactions remains largely unexplored. In this study, we investigated how mowing influences resistance of licorice (Glycyrrhiza uralensis) to the whitefly Bemisia tabaci by integrating behavioral assays with volatile analysis, transcriptomics, and metabolomics. Feeding preference assays showed that adult whiteflies strongly preferred new plants over mowed plants. Developmental assays further revealed that whiteflies exhibited a prolonged egg stage and extended egg-to-adult developmental duration on mowed plants, while adult longevity was not significantly affected. Gas chromatography–mass spectrometry analysis identified 31 volatile compounds in licorice, with alcohols dominating the volatile profile of new plants and terpenoids dominating that of mowed plants. Whitefly infestation significantly increased ester compounds in both plant types. Differential volatile analysis highlighted cis-3-hexen-1-ol and trans-3-hexen-1-ol as dominant compounds in new plants, whereas 3-carene and β-pinene were predominant in mowed plants. Transcriptomic analysis revealed that mowing primarily affected genes associated with primary metabolism and ribosome-related pathways, whereas whitefly infestation induced extensive transcriptional reprogramming, including activation of flavonoid biosynthesis, flavone and flavonol biosynthesis, MAPK signaling, and plant circadian rhythm pathways. Metabolomic profiling identified substantial accumulation of flavonoids, flavonols, and isoflavonoids following whitefly feeding. Integrated multi-omics analysis identified flavonol biosynthesis as a core pathway underlying licorice defense against B. tabaci. Overall, this study demonstrates that mowing primes G. uralensis for enhanced resistance to whitefly infestation by reshaping volatile emissions, activating secondary metabolite biosynthesis, and inducing coordinated defense signaling networks. These findings provide new insights into plant–insect interactions and highlight mowing as a potential component of sustainable pest management strategies.