I was photographing a spider a few days ago, and one frame that I was about to trash (jumping spider’s eyes not in focus) happened to show a kleptoparasitic fly that was drinking fluids from the captured ant. Because the fly is not especially visible I haven’t tried that hard to ID the fly (probably Milichiidae or Chloropidae), but I did find an interesting page showing a fly in Australia that was found near a salticid called an ant eater (Zenodorus orbiculatus).
If you have time to waste, here are some fun facts about kleptoparasitic flies:
- Some species are attracted to volatiles released by captured prey (e.g., stink bugs). I have pics.
- There are apparently some that are specialists on spiders (Brake and von Tschimhaus 2010).
- It’s usually just females; when males present they might be looking for mating opportunities with females (Ibid.).
- In Africa. there’s a milchiid that can induce ants to regurgitate (Wild and Brake 2009).
- Some plants in the Apocynaceae seem to have evolved the ability to mimic the venom volatiles of paper wasps. The scent is attractive to kleptoparasitic flies because the wasps use the venom when they hunt (Heiduk et al. 2015). This is referred to as kleptomyiophily, apparently (new word for me).
If you really need to more, check out the http://www.milichiidae.info/. Sorry: the Chloropidae don’t have their own site.
I think the spider is Phidippus princeps. Happy to be told otherwise. Here are some better pics of the spider: