COI amplicon libraries were constructed using a two-step PCR protocol (Braukmann et al., 2019). For the first PCR the forward primer AncientLepF3 (Prosser et al., 2016) and the reverse primer cocktail C_LEPFoIR (containing LepR1 and HCO2198) (Hebert et al., 2004) were used to amplify a 462 bp region of the COI gene. During the second round of PCR, fusion primers were used to attach IonXpress universal molecular identifiers (UMIs) along with sequencing adaptors to the first round PCR products. The UMI-tagged PCR products were normalised and pooled prior to sequencing on an Ion Torrent S5 high-throughput sequencer.