"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

March 13, 2010

March 16 – Cyclopodia horsfieldi

Huh? A flightless fly? These highly specialized bat flies (Diptera: Hippoboscoidea) feed exclusively on the blood of bats and live their lives clinging mightily to the fur of their volant hosts. Although considered true flies, these derived creatures have lost their wings entirely and evolved specialized structures for ‘swimming’ through or ‘running’ across the fur of their hosts. They have a bizarre life-history, bat flies do not lay eggs, but rather eggs develop internally within the females nourished by uterine “milk” and a single prepupa (3rd instar larva) is deposited on the roost substrate. When young flies emerge, they crawl on to the nearest bat and live out the rest of their life on their host. Interestingly, bat flies are generally quite host-specific but Cyclopodia horsfieldi is known to occur on three species of “flying fox”, or Old-World fruit bats (Pteropus), found in Southeast Asia. If bats aren’t your cup of tea, then an experience with the World’s largest bats teaming with a bunch of wingless blood-sucking flies is sure to induce nightmares!

Contributed by Kevin Olival.


  1. I talk about these on my own website, though focusing on a species which only eats the skin flakes and feces of the host, rather than true parasitism. These are some of my favorite insects!

  2. are there any papers available on this subject?

  3. 'Lack of population genetic structure and host specificity in the bat fly, Cyclopodia horsfieldi, across species of Pteropus bats in Southeast Asia'. See here: http://www.parasitesandvectors.com/content/6/1/231

  4. Thanks for plugging my new paper, Fred!