@kasiaaus ruling out the mud-nesting spider wasps & potter wasps, it’s also possible this could be the larva of one of the parasitoid wasps like the Ichneumon/Braconid Wasps. Apparently their larvae can feed openly on the host like this but I’m still not sure how we can go about verifying the ID without raising the larva☹️
Thank you @DiBickers. I did not see any mud nest nearby so it is probably a fly larva. The spider with the parasite was on a gum tree trunk about 1.5m off the ground.
@kasiaaus if these spiders were found near a broken mud nest it’s likely the grub is a wasp larva. If you found it out in the open with no nest nearby it’s likely this is a fly larva. An example that target spiders are the small-headed flies (Family Acroceridae). Unfortunately, I’ve never seen them ID’d in these instances & the only way to ensure identification is truly accurate would be to raise it and see what hatches after the larva pupates.
