## Materials and Methods
### Sampling, Identification, and Morphology
The final variables used for PCA were the forceps asymmetry index, the paramere length-width ratio, the basal width of the forceps, and the forceps length-width ratio. Twenty-four hours prior to any dissection, specimens were transferred to 70% ethanol to make them more pliable. Parameres were removed by gently lifting the penultimate abdominal skernite and pulling out the entire male genitalia by its attachment to the sperm duct with forceps, and then cutting at the site of attachment. Photos were taken of male forceps and parameres with an IS500 5.0-megapixel camera (Tuscent Photonics, Fuzhou, China) attached to a SMZ1500 stereomicroscope (Nikon, Tokyo, Japan) with a C-Mount Adapter 0.45X (Nikon, Tokyo, Japan) at 40\(\times\) and 80\(\times\) respectively, using ISCapture version 4.1.3 (Tuscent Photonics, Fuzhou, China). A scale bar was photographed at each magnification. To assist repeatability of measurements, the material (either the dissected genitalia or the whole body of the adult specimen) was aligned along its anteroposterior axis to a digital graticule. All photos were taken from the dorsal side. Following this, all specimens were returned to 100% ethanol. Measurements were then taken from the photos using Fiji [62] with the appropriate scale photo used to set the measurement scale (pixels mm\({}^{-1}\)). For length and width measurements (Figure 1o,p,r,s), a bounding box was drawn encompassing the total vertical and horizontal width of each of the forceps and the right paramere. For the forceps, both forceps were measured, and the largest was taken. A random subset of 30 individuals was remeasured twice in a random order to  
Figure 1: (**a**–**n**): Photos of male Anisolabididae forceps and parameres. (**a,b**): _Antisolabis_ sp. 1. (**c,d**): _Antisolabis_ sp. 2. (**e,f**): _Gonolabis_ forcipata_ [PERSON]. (**g,h**): _Gonolabis_ nr. _gilesi_ [PERSON]. (**i,j**): _Gonolabis_ sp. 1. (**k,l**): _Gonolabis_ sp. 2. (**m,n**): _Gonolabis_ sp. 3. (**o**–**s**): Diagrams of morphometric measurements taken. (**o**): Forceps length. (**p**): forceps width. (**q**): basal width of forceps. (**r**): paramere length. (**s**): paramere width. All scale bars indicate 1 mm. Red arrows indicate location of dorsoventrally oriented teeth on forceps of male \(G\). nr. _gilesi_. assess repeatability. Intraclass correlation coefficients were calculated for each measurement, and these ranged from 0.713 (length of the left forceps) to 0.999 (length of the right forceps). Principal component analysis was performed on the scaled and centred morphometric variables. Excluding individuals with missing measurements (damaged forceps or parameres) the morphometric dataset comprised 124 male Anisolabididae specimens. Having morphospecies defined _a priori_ permits a classification analysis. A discriminant function analysis was performed with the morphometric dataset to assess the efficiency of simple linear measurements for species assignments. A first test was performed to assign morphospecies to putative genus, and then to putative species. In the case of the _Gonolabis_ morphospecies, analyses were run both including and excluding \(G\). sp. 3 as this morphospecies was only represented by three individuals, to assess the effect of a small class size on classification accuracy. For each case, the analysis was performed using the whole dataset to assess variable importance, and then with jack-knife cross-validation to assess classification accuracy. Note that classification accuracy was not assessed using a pre-defined proportion of training and test observations, because of the small size of the datasets (total N = 124, N\({}_{Anisolthis}\) = 30, N\({}_{Gonolabis}\) = 94 or 91 excluding \(G\). sp. 3).