Oldest record of a larva of long-legged velvet mite (Erythraeoidea) parasitising an immature planthopper

Abstract

The fossilization of organisms in amber displaying the behaviour in which they were engaged when becoming entrapped in tree resin is known as “frozen behaviour” (Arillo, 2007). Findings of frozen behaviour are rare and can uncover valuable information on how food webs were structured in the past. One of the most reported interactions between organisms in amber is the case of parasitengonan mites still attached to their hosts (De Baets et al., 2021). Parasitengona is an ingroup of Trombidiformes characterised by a complex life cycle (Krantz & Walter, 2009) in which the active post-larval forms (deutonymph and adult) are predatory, while the six-legged heteromorphic larva (for challenges of the term, see Haug, 2020) is parasitic on euarthropodan and vertebrate hosts (Mąkol et al., 2012). Given the firm grip of most parasitengonan mites to their hosts (e.g., Åbro, 1988), these mites are often found in amber still attached to them (De Baets et al., 2021). Among Parasitengona, there is an ingroup characterised by their extremely long legs (Wohltmann, 2000), Erythraeoidea, or long-legged velvet mites. Erythraeoidean larvae parasitise several euarthropodan groups, with few exceptions (Stroiński et al., 2013). Most known hosts from the fossil record are dipterans (as reviewed by Arillo et al., 2018; Arce et al., 2024), with a few reports on other insects: a moth (Poinar et al., 1991), a spider and a booklouse (Weitschat & Wichard 1998), and a cicada (Poinar et al., 2012). Here we report a piece of Kachin (Myanmar) amber of ca. 100 Mya with a mite attached to a planthopper. We further discuss its implications for the host-parasite relationship of Erythraeoidea.