Another strange holometabolan larva from Kachin amber—the enigma of the beak larva (Neuropteriformia)

Abstract

Holometabolan larvae are dominating components of modern terrestrial and freshwater ecosystems and have a significant ecological impact. Also in past ecosystems, various types of such larvae have been present, which is especially well known from ambers from all over the world. During the Cretaceous, holometabolan larvae with a very modern appearance co-occur with those of morphologies totally unknown in the ecosystems of today. One of these morphologies only known from ca. 100-million-year-old Kachin amber from Myanmar is represented by the so-called “beak larvae”, which possess an anteriorly projecting beak-like mouth cone, previously being described from two specimens. We describe here a third specimen as a new species, ?Partisaniferus edjarzembowskii sp. nov. This new species differs from the previously described beak larva species Partisaniferus atrickmuelleri in the shape of the trunk end as well as in lacking a differentiation of the tergites into distinct sclerites and in the absence of abdomen protrusions. We discuss possible aspects of the ontogeny of the beak larvae, including the possibility that the here described specimen and one of the previously known ones are different larval stages of ?P. edjarzembowskii sp. nov. Furthermore, we discuss possible relationships of beak larvae within Neuropteriformia.