Hoverfly - Common Banded (Syrphus ribesii)

Common Banded (Syrphus ribesii) Size 7.25-11.5mm. Flight. Apr-Nov

Species of the week – 13th October
 

As the nights draw in and the days get colder, windier and wetter the chances to see hoverflies decrease. However, on those warmer days, with a little searching for that hoverfly hotspot, they can be found. One of the species still around in numbers is the Common Banded hoverfly (Syrphus ribesii). They are one of those species where the common in the name does actually mean its common unlike Common Snipe Gallinago gallinago or Common Crane Grus grus. Other names for it are the Common Flower fly, as they are often referred to as flowerflies not hoverflies in the Americas. It is also known as the Humming Banded fly, a naming more related to its behaviour, and one I prefer, if it should become less common.

I’m sure we have all seen deer leks on TV, or maybe fortunate enough to have seen a Black Grouse Lyurus tetrix lek. In each the males congregate to strut their stuff, showing their genetic vigour to win over the females. Well, it might surprise you to know that hoverflies also lek. Several hoverfly species are known to lek but the Common Banded does it with a hum.

I have often observed Common Banded males sitting on a leaf, in a sunny spot, beating their wings, which is what makes the humming sound. I have since discovered you can amplify the sound with a bat detector, set to 15-20khz, so other people can hear it too. What they are doing is considered a mating call, advertising to a female a flower, which the male is diligently guarding. They can also hover about 2-5 metres above the ground and if you hold your hand out, they may even settle for a little rest. But just check it's not a Marmalade (Episyrphus balteatus), Common Dronefly (Eristalis tenax) or Tapered Dronefly (Eristalis pertinax) as these often lek and hover in the same airspace. It’s one of natures’ joys to see several males in a shaft of sunlight all dancing and lekking together.

The larvae are aphid predators, and I often find them amongst my flowers in my wild garden, particularly on Oxeye daises Leucanthemum vulgare. They can come in a range of colours from whitish green, red to yellow brown. Down the central spine of the larva are dark patches resembling chevrons. This patterning gives it at 1st glance the resemblance of bird poo, a mimics trick to avoid being eaten. Alternatively, I have found them on the underside of Sycamore Acer pseudoplatanus leaves, no doubt what Blackbirds Turdus merula are looking for when you see them turning over the leaves in the ground cover. So please give a thought when you clear up your leaves into dustbins for collection or burn them, be mindful that not only are you killing potential hoverflies but taking away essential food for birds, hedgehogs, and other little critters.

There are 5 known UK & European Syrphus species, each having a yellow and black banded abdomen, bottom 2 more moustache shaped, a yellow face with a black nose and green bronzy thorax. They also have a hairy upper surface on the squama, see picture below and is an identification feature which distinguishes it from other similar tribes Epistrophe or Parasyrphus. It is however a very difficult feature to see in the field, and I would not encourage you to kill it to be sure, as there are better ways to identify them.

Diagram of the main parts of a Common Banded (Syrphus ribesii) wing.

There are two other common species to this tribe, Hairy-eyed Banded (Syrphus torvus) and Glass-winged Banded (Syrphus vitripennis), the other two S.rectus and S.nitidifrons are rare and continental and there is doubt with the former of it even being a British resident.

The common nature of these 3 species along with the difficulty to separate them in the field often results in mistakes, which I have often made. As a rule, Hairy-eyed are more prevalent in March-April, midsummer for Glass-winged and autumn for Common Banded, but to be frank I have found Common Banded most months, so not a reliable method for identification.

Below are some tips to aid identification:

To separate female Common Banded (separated eyes) from Hairy-eyed & Glass-winged.

• ·   Check the hind femur which are totally orange or black at the base, the part of the rear leg closet to the abdomen.

To separate male Common Banded (no gap between eyes) from Hairy-eyed.

• With a lens x20 check if there are hairs on its eyes, a feature that should be obvious in males’ less so in females. – if hairs then not Common Banded or Glass-winged but Hairy-eyed.

To separate male Common Banded (no gap between eyes) from Glass-winged.

• If segment 1-5 of the front and middle tarsi are black, then Common Banded or else if yellow then Glass-winged.
• For completeness 2^nd Basal cell of the wing is only half covered in microtrichia (tiny hairs) for Glass-winged, while the 2^nd Basal cell is fully covered for Common and Hairy-eyed. You need a dead specimen and microscope to confirm as it is not something possible to identify in the field.

So, when next you are out next naturalising look out for the Common Banded hoverfly or turn over a leaf in the leaf litter to see if you can spot its larvae. Let me know if you find any in the comments below.