BAT FLY

Mystacinobia zelandica

This blind, wingless fly is entirely dependent on a supply of guano and the warmth of a bat roost to survive. First discovered on a bat in the 1950s, it wasn’t until Kopi, a famous kauri (Agathis australis) in Omahuta, Northland, collapsed under its own weight in 1973 that the bat fly was formally described. A few specimens were found on a shorttailed bat that had been killed when Kopi fell, and were sent to Beverley Holloway, an entomologist working at the Department of Scientific and Industrial Research (DSIR) who gained her PhD in biology at Harvard and was awarded the New Zealand Commemoration Medal.

Description: This species is 4–9mm long with specially adapted long bristly claws which help with movement in bat fur. Males are larger than females and have hairier thoraxes, with females having larger and more distended abdomens.

Habitat and distribution: In the wild, the bat fly lives only in tree roosts of the nationally threatened endemic short-tailed bat (Mystacina tuberculata) in a very few places across Aotearoa New Zealand, but it is believed that its ancestors evolved in Australia.

Biology: There can be thousands of bat flies of all life stages from egg to adult in a bat roost inside a tree hollow, living on the guano-coated walls. Some adults, mostly gravid females, will cling to bats, potentially the founders of a new colony should the bats abandon a fallen tree. Research suggests that these insects need temperatures approaching 30°C to prosper; without bats to generate heat inside the enclosed space of a roost, individual bat flies will soon die. Males live longer than females. Older males that have already mated may produce sound, possibly to deter bats from feeding on the flies – the bats normally consume insects, as well as pollen, which is cleaned and consumed by the flies while grooming the fur of the bats. Related species overseas are parasitic on the bats they live with, while the endemic species lives in a commensal relationship with the bats.

Status in Aotearoa: Endemic