Peter Convey

True insects are something of an oddity in the Antarctic, at least since taxonomists have taken the springtails (proper name Collembola) and placed them ancestral to rather than within the insects themselves. If we confine ourselves to the Antarctic continent, in fact there are only two of them, although there are a few more on the sub-Antarctic islands (of which more later….). The two properly Antarctic ones are both midges (family Chironomidae). As often happens when you look closely at something small, they turn out to have some particularly interesting characteristics. One species, Parochlus steinenii, is the only flying insect in the Antarctic. It is a South American species which has a toehold – actually a bit more than that since swarms of the adults are visible on the rare calm days – in the South Shetland Islands and on sub-Antarctic South Georgia. The other, Belgica antarctica, has wings that are reduced to tiny stubs (‘brachyptery’), and does its swarming on the ground and moss vegetation when warmed by the sun. The photograph, courtesy of my colleague Rick Lee, shows a mating pair of these ~5mm midges. Belgica is a particularly interesting species, as it is endemic (i.e. only occurs on) the Antarctic Peninsula and South Shetland Islands. This leads to an obvious question of ‘how long have they been there?’ – on the one hand it takes a long time for new species to evolve, but on the other hand, this part of Antarctica is very heavily glaciated – there is very little land and habitat even now – and was more so only ten thousand years ago at the last glacial maximum. Could its habitat, and the fly itself, have survived through the ice ages in Antarctica? Modern molecular biology techniques seem to answer this question with a resounding ‘yes’ – dating the split from Belgica’s nearest known relative (a fly from sub-Antarctic South Georgia, where it is also endemic) at more than 40 million years ago. On the face of it, this is a small and specialised observation…but it has huge implications…if the fly has survived on the Antarctic Peninsula for that length of time, then obviously its habitat must have too, which means we need to revise our thinking about how much more ice there was on Antarctica during ‘ice age’ periods.