Articles | Volume 20, issue 2
Research article
25 Aug 2017
Research article |  | 25 Aug 2017

The wasp larva's last supper: 100 million years of evolutionary stasis in the larval development of rhopalosomatid wasps (Hymenoptera: Rhopalosomatidae)

Volker Lohrmann and Michael S. Engel

Abstract. Rhopalosomatidae are an unusual family of wasps (Hymenoptera: Aculeata) comprising less than 100 species found in the tropics and subtropics of all continents except Europe and Antarctica. Whereas some species resemble nocturnal Ichneumonidae, others might be mistaken for spider wasps or different groups of brachypterous Hymenoptera. Despite their varied morphology, all members of the family supposedly develop as larval ectoparasitoids of crickets (Orthoptera: Grylloidea). Here, we report on the first record of a fossil rhopalosomatid larva which was discovered in mid-Cretaceous amber from northern Myanmar (Burma). The larva is attached to the lateral side of a cricket between the metafemur and the abdomen, impacting the natural position of the hind leg, exactly as documented for modern species. Additionally, the larval gestalt is strikingly similar to those of extant forms. These observations imply that this behavioral specialization, e.g., host association and positioning on host, likely evolved in the stem of the family at least 100 million years ago.

Short summary
Amber functions as a window into the past, capable of capturing behaviors frozen for millions of years. Here, we report on the exceptionally rare discovery of a dinosaur-age larva of a stinging wasp, feeding on its cricket host, in mid-Cretaceous amber from Myanmar. It reveals a considerable constancy in the biology of this particular family over the last 100 million years. The excellent preservation of the larva is remarkable and due solely to the fidelity permitted by inclusion in amber.