Another one bites the plastics.

Old-growth forests host a rich diversity of invertebrate assemblages. Among them, saproxylic insects play a fundamental role in the nutrient cycle and ecosystem functioning. In these environments, coevolution between insect and plants have reached a stable equilibrium over millions of years. These delicate ecosystems are threatened mainly by habitat loss and fragmentation, and to date, they have to face the new "plastic threat." Plastics are widespread in all biomes and ecosystems accumulating throughout the years due to their low degradation rate. Once accumulated, large pieces of plastics can be degraded into smaller particles, the latter representing a great threat to biodiversity and ecosystem health, producing detrimental effects on biota. Since the effects of plastics on terrestrial systems remain largely unexplored, this study aimed at contributing to increasing the knowledge on the interaction between plastics and terrestrial biota. We put our emphasis on the novel and broad topic of plastic degradation by saproxylic beetle larvae, describing how they fragmented macroplastics into microplastics. To investigate whether saproxylic cetonid larvae could degrade expanded polystyrene, we performed an experiment. Thus, we put larvae collected in the field in an expanded polystyrene box. We observed that larvae dug in the thickness of the box fragmenting macroplastics into microplastics and producing a total of 3441 particles. Then, we removed the larvae from the EPS box and isolated them in glass jars filled with natural substrate. The substrate was checked for EPS microplastics previously ingested and now egested by larvae. Additionally, we pointed out that plastics remained attached to cetonid larvae setae, with a mean number of 30.7 ± 12.5 items. Although preliminary, our results highlighted that microplastics attached to saproxylic cetonid larvae might be transported into habitats and transferred along the food web. In conclusion, plastic pollution might affect vulnerable species and ecosystem services representing a risk also for human health.

Antennal fine morphology of the threatened beetle Osmoderma eremita (Coleoptera: Scarabaeidae), revealed by scanning electron microscopy.

The aim of this study was to characterize the antennal morphology of Osmoderma eremita, a threatened scarab beetle inhabiting tree hollows. O. eremita males produce a sex pheromone, (R)-(+)-γ-decalactone, responsible mainly for the attraction of females but also other males. Gross and fine morphology of microstructures including sensilla, microsculpture and pores were analyzed using Scanning Electron Microscopy. The antenna of O. eremita showed the typical lamellicorn shape of scarab beetles, with a basal scape, a pedicel, a funicle composed of five antennomeres and a club composed of three lamellae. Six different subtypes of sensilla chaetica (Ch.1 - 6), Böhm sensilla (Bo), one subtype of sensilla basiconica (Ba.1), two subtypes of sensilla coeloconica (Co.1 - 2), two subtypes of sensilla placodea (Pl.1 - 2), pores and peculiar folds were described. The two sexes did not show any significant differences in the occurrence and number of the sensilla placodea, known to be responsible for the pheromone reception. Instead, some sexual differences were found on the occurrence and topology of three different microstructures: (1) one subtype of sensillum chaeticum (Ch.2) occurring on the pedicel only in males; (2) a characteristic pore occurring on the funicle only in males; (3) a peculiar fold occurring on different antennomeres of the funicle in the two sexes, on the fourth in males and on the fifth in females. A comparison between sensilla of O. eremita and those of other Scarabaeoidea is provided.

Exaggerated allometric structures in relation to demographic and ecological parameters in Lucanus cervus (Coleoptera: Lucanidae).

Enlarged weapons and ornamental traits under sexual selection often show a positive allometric relationship with the overall body size. The present study explores the allometry of mandibles and their supporting structure, the head, in males of the European stag beetle, Lucanus cervus. This species shows a remarkable dimorphism in mandible shape and size that are used by males in intraspecific combats. Stag beetles were captured, measured, weighed, and released in the framework of a capture-mark-recapture study. The relationship of mandible length (ML) and head width in respect to the overall body size was described by a segmented regression model. A linear relationship was detected between ML and head width. The scaling relationships for both ML and head width identified the same switchpoint, highlighting the advantages of using combined results of weapons and their supporting structures in such analysis. These results led to a more consistent distinction of males in two morphologies: minor and major. The survival probability of individuals was dependent on the morphological class and was higher for minor males than for major. Elytron length and body mass of the individuals did not show any significant variation during the season. Differences in predatory pressure were detected between morphs by the collection and analysis of body fragments due to the predatory activity of corvids. Morphological differences and shift in demographic and ecological parameters between the two classes suggested that selection continues to favor intrasexual dimorphism in this species throughout a trade-off mechanism between costs and benefits of carrying exaggerated traits.