Hi Kim There are good photos (Reiner Richter) on ALA: https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:409bd0dc-71fd-4259-ba43-4b7dde4fca95#gallery
P.erythinus has a deep orange-red colour and orange patterning on the top of its thorax - P. humilis is a washed out brown -orange without the back patterning.