## Materials and Methods
### Barcoding  
To corroborate the morphospecies assignment by male characters, sequences of a 658 bp fragment of the cytochrome \(c\) oxidase subunit 1 gene (_cox1_) were obtained from selected individuals of each morphospecies across the sites at which they were found. Known species (_F. auricularia_, _N. lividipes_, _L. truncata_) were barcoded first. A few individuals (1-4, depending on the abundance at a site) were sequenced from at least 3 populations in each state to assess the barcode gap for widely distributed species. While barcode gaps may hold in the face of broad distributions [63; 64], it is unknown how geographically structured dermatapteran populations are, and so local-scale barcode divergence may confound the utility of the method. The number of individuals of each Anisolabididae morphospecies barcoded was largely determined by their individual abundances and their successful amplification. After successful retrieval of barcode sequences for male specimens, sequences for unknown female specimens were obtained. Individual females were selected based on their co-occurrence with males of each morphospecies. Females that fell within the range of genetic distance for a given male morphospecies (assessed visually using a neighbour-joining tree of p-distances generated in MEGA X [65]) were used to define adult female morphology for the morphospecies. All remaining adult females in the sample were then identified  
Total genomic DNA extractions were performed using Chelex resin (Bio-Rad, Hercules, CA, USA) [66]. One of the mesothoracic legs was removed from individuals using forceps, taking care not to damage the body in the process and flame-sterilising instruments with 100% ethanol between handling different individuals. Excised legs were placed in 1.7 mL tubes with 200 \(\upmu\)L 5% Chelex in solution and two 3 mm diameter glass beads, and then shaken in a TissueLyser II mixer mill (Qiagen, Venlo, The Netherlands) at 25 Herz for two minutes, following which the mixer mill adaptor plates were reversed in orientation and the tubes shaken for another two minutes. Tubes were spun down in a desktop centrifuge briefly and 5 \(\upmu\)L of Proteinase-K (Bioline, London, UK) was added directly to the surface of the Chelex. Tubes were incubated in a water bath at 65 \({}^{\circ}\)C for two hours, followed by 10 min at 90 \({}^{\circ}\)C to deactivate the Proteinase-K. Extractions were stored at \(-\)20 \({}^{\circ}\)C. Prior to PCR, tubes were spun down at 18,600 ref (\(\times\) g) for seven minutes in a D3024 high-speed microcentrifuge (DLAB Scientific, Beijing, China), and aqueous DNA was pipetted from just above the surface of the Chelex. We first used the \"universal\" arthropod primer pair LCO1490/HCO2198 [67] and where these failed used the revised degenerate versions jgLCO1490/jgHCO2198 [68]. DNA was amplified using 1 \(\upmu\)L of total genomic extractions as templates in a 40 \(\upmu\)L reaction with 1\(\times\) Thermopol PCR buffer (New England Biolabs, Ipswich, MA, USA), 2 mM MgCl\({}_{2}\), 200 \(\upmu\)M dNTPs, 1 \(\upmu\)M of each primer, 0.64 \(\upmu\)g bovine serum albumin, and 1.6 U of _taq_ polymerase (New England Biolabs, Ipswich, MA, USA). Initial denaturation took place at 95 \({}^{\circ}\)C for four minutes, followed by 40 cycles of 95 \({}^{\circ}\)C denaturation for 30 s,49 \({}^{\circ}\)C annealing for 60 s, and 72 \({}^{\circ}\)C extension for 90 s, followed by 72 \({}^{\circ}\)C for three minutes for the final extension using a Mastercyler EP Gradient S thermocycler (Eppendorf, Hamburg, Germany). Products were run on a 2% agarose gel set with SYBR Safe DNA Gel Stain (ThermoFisher, Waltham, MA, USA) at 100 eV for 40 min, and then visualised with GelDoc XR+ (Bio-Rad, Hercules, CA, USA) using the default setting for SYBR stained DNA. Products were directly sequenced in both directions using the respective primers with an Applied Biosystems 3730 capillary analyser (Macrogen, South Korea). and others: sequence data were generated with Sanger sequencing.