Neoichnologic Experiments with Modern Scarabaeid Beetle Larvae: Implications for Backfilled Trace Fossils in Permian Continental Deposits, Hugoton Gas Field, Western Kansas

Counts, John W.¹, Stephen T. Hasiotis¹ (1) University of Kansas, Lawrence, KS

We describe laboratory experiments designed to understand better the burrowing abilities, mechanisms, and morphologies of modern beetle larvae of June beetles (Scarabaeidae: Melolonthinae). Our objectives are two-fold. We wanted to compare these structures to various burrow morphologies in Permian deposits of western Kansas. Previous research by paleoentomologist and ichnologists suggest that insect larvae cannot produce backfilled burrows, understating the ability of terrestrial arthropods to significantly bioturbate subaerially exposed deposits.

Beetle larvae were placed in narrow glass enclosures containing finely laminated, moist (~10-30%), medium- to fine-grained sand. They were allowed to burrow for several days, during which time the burrowing mechanisms and burrow morphologies were photographed and videotaped. Beetle larvae produced tortuous subvertical to subhorizontal burrows composed of discrete packets of meniscate backfills by excavating a void space in front of them with they jaws and carrying material to the back of this space by somersaulting and packing it with their heads.

Individual traces and bioturbation patterns produced are remarkably similar to adhesive meniscate burrows (AMB) in Lower Permian loess deposits, which form part of the Hugoton Gas Field, western Kansas. We hypothesize that the Permian tracemakers were beetle larvae with body plans similar to extant scarabaeid beetle larvae. The presence of AMB is diagnostic of subaerial exposure and paleosol formation, and thus, useful for recognizing sequence boundaries and sea-level lowstands. Such burrows may act as fluid barriers or fluid conduits, affecting hydrocarbon migration because bioturbation results in grain repacking and sediment transport. Results of neoichnologic experiments with terrestrial organisms underscore the need to reevaluate paleoenvironments and ichnofossils interpreted originally as subaqueous in origin.