Freak of the Week: Wingless, Legless Flies

I found this while looking up identification info for phorid flies, of which we currently seem to be receiving something of an influx in our samples.


Photoes from here.

Most of what you see in the lower of the two photoes above are larvae of army ants of the genus Aenictus. The odd one out is the whiter 'larva' in the centre—which is not a larva at all, but a fully adult female of the phorid fly Vestigipoda longiseta! (The upper photo shows the same animal in close-up.) This bizarre animal makes its living by imitating its host larvae and being fed by the larvae's deluded carers. Five species of Vestigipoda have been described to date from Malaysia (Disney et al., 1998; Murayama et al., 2008).


Close-up of head of Vestigipoda maschwitzi, from Disney et al. (1998).

Cases of neoteny, where insects develop full sexual maturity while still 'larvae', are not unknown among holometabolous insects (I earlier described a case involving the beetle Micromalthus). However, Vestigipoda cannot be regarded as neotenous because the female has a fully developed adult head.

So far, Vestigipoda seems to only be known from females. It is possible that males, when found, may turn out to be much more normal phorid flies. The challenge would be recognising them as related to their bizarre females.

REFERENCES

Disney, R. H. L., A. Weissflog & U. Maschwitz. 1998. A second species of legless scuttle fly (Diptera: Phoridae) associated with ants (Hymenoptera: Formicidae). Journal of Zoology 246 (3): 269-274.

Maruyama, M., R. H. L. Disney & R. Hashim. 2008. Three new species of legless, wingless scuttle flies (Diptera: Phoridae) associated with army ants (Hymenoptera: Formicidae) in Malaysia. Sociobiology 52 (3): 485-496.