Earliest evidence of insect endophytic oviposition

The knowledge of fossil plant-insect interactions is almost entirely restricted to evidences of feeding behavior. Records of endophytic oviposition are relatively scarce, with previous earliest reports from the Middle to the early Late Triassic. Nevertheless, several Paleozoic insect taxa have been suspected of this reproductive behavior, but without any direct evidence. Specimens of Calamites cistii (Sphenophyta; Pennsylvanian, France) are described showing endophytic cavities, located in the outer cortex of the stem, a tissue that is rarely preserved. This new record shifts the appearance of this behavior back 60 Ma. Possible tracemakers are representatives of the Odonatoptera (Odonata and related extinct taxa), Palaeodictyopteroidea (extinct palaeopterous orders), and Archaeorthoptera (Orthoptera and related extinct orders). The antiquity of the insect endophytic oviposition behavior suggests that it could have been important during the emergence and diversification of the insect group.