A case of frozen behaviour: A flat wasp female with a beetle larva in its grasp in 100-million-year-old amber

Abstract

Parasitism, a malignant form of symbiosis, wherein one partner, the parasite, derives benefits to the detriment of another, the host, is a widespread phenomenon. Parasitism sensu lato is understood here to include many phenomena, like parasitoidism, kleptoparasitism, phoresy and obligate parasitism. Insecta has many in-groups that have evolved a parasitic life-style; one of the largest in-groups of these is probably the group of Hymenoptera. Bethylidae, the group of flat wasps, is a smaller in-group of Aculeata, the group of hymenopterans with venom stings; representatives of Bethylidae are parasitic. They are more specifically larval ectoparasitoids, meaning that their immature stages are externally developing parasites that kill their host organism at pupation (end of interaction). They mostly parasitise immature representatives of Coleoptera and Lepidoptera. Female flat wasps search for a host for their progeny, paralyse it with their venom sting and then oviposit onto it. Herein we describe one of the oldest findings of parasitic interactions of parasitoid wasps with their progenies’ hosts, specifically a flat wasp female grasping and (potentially) stinging a beetle immature in Cretaceous Kachin (Myanmar) amber (ca. 100 million years old). This finding indicates that this type of parasitic interaction existed since the Cretaceous, temporally close to the earliest findings of representatives of Bethylidae.

Fossils in Myanmar amber demonstrate the diversity of anti-predator strategies of Cretaceous holometabolan insect larvae

“…Most cases are restricted to the mere presence of adults for which we know that in the modern fauna their larvae are parasitic. A single wasp of the group Bethylidae (flat wasps) is so far known from Kachin amber preserved while stinging into a possible host for its offspring ( Figure 7 B; 81 ), indicating that the wasps offspring lived parasitic on a larger beetle larva. New specimens indicate that not only beetle larvae were possible hosts, but also snakefly larvae ( Figure 7 A) and lepidopteran caterpillars ( Figure 7 C).…”

Driven apart: fossil parasitic long-legged velvet mite larvae on gall midges represent a long lost parasitic association between mites and dipterans

“…Parasites rule this world (Klompmaker et al, 2014). This includes parasites in the strict sense (i.e., feeding on their hosts; Nelson et al, 1975;Haug et al, 2018;Gorb et al, 2022), but also parasitoids (which ultimately kill their hosts; Hassel & Waage 1984; Kiesmüller et al, 2022;Fei et al, 2023) and complex aspects such as brood parasitism (Zink, 2000;Suhonen et al, 2019;Sless et al, 2023) or kleptoparasitism (Sivinski et al, 1999;Shopido et al, 2019, but see van der Wal et al, 2021. Due to the overwhelming presence of all these life strategies (parasitism in the wide sense), we can assume that this has also been the case quite some time ago.…”