The strange flightless fly that can be found cosying up with bats
Nick Baker’s HIDDEN WORLD The popular naturalist, author and TV presenter reveals a secret world of overlooked wildlife
NEW ZEALAND BAT FLY
There’s a fly that doesn’t have wings and a bat that doesn’t use the ones it has as much as you might expect. Both these evolutionary oddballs live side by side in a weird marriage made in heaven… or rather New Zealand. The New Zealand bat fly (Mystacinobia zelandica) is found hanging around and on the furry bodies of the country’s only endemic mammals, bats, and one species in particular: the New Zealand lesser short-tailed bat, with which it shares an intimate and unique relationship.
The concept of a fly on a bat isn’t surprising, as bats worldwide are riddled with all kinds of ectoparasitic flies, as well as mites, lice and fleas. Most of these flies feed on bats’ blood, but not in New Zealand. It is thought that the ancestors of the country’s bats arrived before parasites had evolved to exploit them – about 79 million years ago, when New Zealand parted company with Gondwana. Consequently, living in isolation on these islands, they’ve developed a totally different relationship with a totally different fly.
The New Zealand bat fly is different in many ways. For a start, it doesn’t look like a fly at all, lacking a pair of wings. It has
given up flight and appears to be more like a scuttling spider missing a pair of legs. It doesn’t need eyes either. Instead, it is equipped with bristles to sense and feel, and each leg is adorned with large hooks – helpful if you need to cling onto a bat’s fur. But it’s the fly’s behaviour that is of particular interest to biologists.
In nature, when you find two unrelated
species living in such intimacy, there is often a transaction of some kind going on – most often a parasitism. But unlike so many of their kind, New Zealand bat flies
don’t appear to be freeloading off their hosts. Analysis of their stomach contents showed they didn’t contain any bat blood, just fruit and pollen. All they were stealing was a little body heat, which may not be insignificant in New Zealand’s often cool and temperate climate.
Still, without wings and without a
hematophagous habit, it was a puzzle that had scientists miffed. What were they feeding on? How did they get pollen if they couldn’t fly about
