letting nature back in

Long-nosed Tangle-veined Flies need to be accurate on the wing when hovering to line up the long proboscis to suck nectar from tubular flowers. These amazing flies are interesting to watch and tricky to photograph.

Tangle-veined flies (Nemestrinidae) occur in many parts of the world with about 300 species in 34 genera. The Field Guide to Insects of South Africa states that there are “48 species of these rather rare flies known from the region”. It also says that little is known about the larval stages of the species in the region, adding that elsewhere in Africa they are known to be quite common parasites of locusts. Wikipedia notes that the larvae are endoparasitoids of either grasshoppers of scarab beetles and that some are considered important in the control of grasshopper populations.

A Tangle-veined fly at rest on a the leaf of a brinjal plant in the vegetable garden

I seldom see these flies at rest, but when I eventually did, I could see that they do not roll up the long proboscis as a butterfly does, but when at rest they tuck it back between their legs. In some species of Tangle-veined Flies the proboscis is absent. At the opposite extreme, such as in the Mega-proboscid Tangle-veined Fly, which occurs in the southern region of the Western Cape (South Africa), the proboscis – specially adapted to pollinating long-tubed flowers – can be an impressive 70 mm in length relative to a wingspan of 40-45 mm.

This Tangled-vein Fly is settled on a leaf with its proboscis tucked back between the legs. The proboscis is about the same length as its body. The orange background is formed by flowers of the Wild Dagga (Leonotis leonurus)

The Tangled-vein Fly is at its most impressive when feeding on the wing. While hovering it lines up a flower in order to be able to insert the long proboscis into the tube. It continues to hover while it sucks up the nectar. There is a sucking pump-like mechanism in the head to enable it to do this.

A Tangle-winged Fly approaching a flower

The fly carefully lines up its proboscis before inserting it down the mouth of the flower’s tube

Another successful alignment

The Tangle-veined Fly continues to hover while sucking up nectar from a flower of a Ribbon Bush (Hypoestes aristata)

Although I know little about these flies, I would hazard a guess that the flies photographed at the Ribbon Bush in our garden might be a Bent-wing Tangle-veined Fly (Stenobasipteron wiedemanni), a species found in the eastern part of South Africa frequenting forests and forest margins.

A Tangle-veined Fly flying with its long proboscis dangling before lining up at another flower for another feed

Tangle-veined Flies are said to buzz loudly while hovering over a flower. I can’t say that I have particularly focused on that – perhaps it is something I have taken for granted without paying proper attention.

I have mostly noticed these flies nectaring when the Ribbon Bushes are flowering during autumn and winter, but I have also seen long-tongued flies in the herb garden when the Basil is in flower. It is possible that this fly (below), seen in silhouette with its fast-moving wings ablur, is another species.

 Sources: Picker, Mike, Griffiths, Charles & Weaving, Alan. 2019. Field Guide to Insects of South Africa. Cape Town: Struik Nature; Wikipedia. 2018. Nemestrinidae. https://en.wikipedia.org/w/index.php?title=Nemestrinidae&oldid=844643685

Posted by Carol