Madra-Bielewicz, A. | Search bioRxiv

bioRxiv2023

Response of adult carrion beetles Necrodes littoralis (L.) (Staphylinidae: Silphinae) to selected cadaveric volatile organic compounds: laboratory and field tests

Carrion insects need to quickly and accurately locate a suitable carcass to maximize their reproductive success. They are attracted by cadaveric volatile organic compounds (VOCs). However, very little is known about VOCs that attract insects at later stages of carrion decomposition. Here, we tested the response of Necrodes littoralis (Linnaeus, 1758). (Staphylinidae: Silphinae), a Palearctic beetle that colonizes large carrion late in decomposition, to selected VOCs. First, in the laboratory choice tests we demonstrated that the beetles reveal no preference for meat with larval blow flies over meat alone. This finding indicates that both, the fly larvae and the feeding matrix they form on meat are not the source of specific attractants for the adult beetles of Necrodes Leach, 1815. Therefore, we focused on VOCs that are related to carrion putrefaction. We tested the response of the beetles to benzyl butyrate, butan-1-ol, butyric acid, cadaverine, dimethyl disulfide (DMDS), dimethyl trisulfide, indole, phenol, putrescine and skatole in laboratory choice assays and field trapping tests. None of the compounds elicited the positive and significant response of the beetles under laboratory or field conditions, indicating that these VOCs are probably not the attractants of N. littoralis. Moreover, in the field tests we found a significant attraction of Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) to traps with DMDS. DMDS revealed also a positive (however insignificant) response of Saprinus spp. (Coleoptera: Histeridae) and Sarcophaga spp. (Diptera: Sarcophagidae). Sarcophaga flies were also attracted to traps with butyric acid. These findings expand the knowledge on chemoecology of carrion insects, highlighting the need to further search for VOCs that attract late-colonizers of carrion.

zoology↗

bioRxiv2019

Heat production in carrion biofilm formed by communally breeding carrion beetles

Insects regulate their body temperature mostly behaviourally, by changing posture or microhabitat. These strategies may be ineffective in some habitats, for example on carrion. Carrion beetles create a feeding matrix by applying to cadaver surface anal or oral exudates. We tested the hypothesis that the matrix, which is formed on carrion by communally breeding beetle Necrodes littoralis L. (Silphidae), produces heat that enhances insect fitness. Using thermal imaging we demonstrate that heat produced in the matrix formed on meat by adult or larval beetles is larger than in meat decomposing without insects. Larval beetles regularly warmed up in the matrix. Moreover, by comparing matrix temperature and larval fitness in colonies with and without preparation of meat by adult beetles, we provide evidence that formation of a matrix by adult beetles has deferred thermal effects for larval microhabitat. We found an increase in heat production of the matrix and a decrease in development time and mortality of larvae after adult beetles applied their exudates on meat in the pre-larval phase. Our findings indicate that spreading of exudates over carrion by Necrodes larvae, apart from other likely functions (e.g. digesting carrion or promoting growth of beneficial microbes), facilitates thermoregulation. In case of adult beetles, this behaviour brings distinct thermal benefits for their offspring and therefore may be viewed as a new form of indirect parental care with an important thermal component.

ecology↗