The other day after work the sunshine encouraged to visit Solutia Meadows, Newport Wetlands. This is a series of wet meadows that is managed by the Gwent Wildlife Trust. It was hot, 30C, and so I was trying to walk slowly admiring the abundance of flowers and Meadow Brown Butterflies around my feet. Then I felt a sharp prick on my arm caused by a Twin-lobed Deerfly having a good old time biting me.
A member of the Tabanidae or Horsefly Family, Chrysops relictus is a smart beast. It’s not as large as some of the other Tabanidae, with a length of 8 to 10.5 mm. The patterning may vary slightly but there are always black lobes on the second abdominal segment. The fly is named after the twin lobe markings on the abdomen (1,2). It also has iridescent green eyes, common to many of the Tabanidae, though this isn’t really evident in my photos. It was a challenge to twist my arm enough to get the iPhone in position to take the photo. Luckily there was no one else around to watch my contortions. There are plenty of great photos on the web that show the eyes in fantastic detail.
I wasn’t able to find much detailed information on the host range of Chrysops relictus, nor it seems of any other European Chrysops species. Chrysops relictusis known to feed on large mammals including cattle, horses and deer (no surprise there). However, it is also much more ready to bite man than many tabanid species (3), and I can vouch for that point. It is only the females that bite and suck blood. They have mouth parts with blade like appendages that can easy cut through tough animal skin. The males feed on nectar. With agriculture the Tabanidae can be a pest in the dairy industry as the carry diseases, infecting cattle and rehung milk output (4).
The larvae feed upon organic matter in damp soils, and are termed hydrobionts in that they inhabit areas of high water content. Here they predate other invertebrates in wet mud and debris at the margins of streams and pools (5). They can paralyse their prey by injecting them with venom, which also pre-digests the grub allowing the horse-fly larva to suck their victim dry. The larvae pupate just below the surface, and over-winter in this state. The adult flies emerge through small holes in the mud in May, and are on the wing until September (4).
If you want to find one, it should be relatively easy if you stand around long enough in wet woodlands, shaded bogs, fens and marshes (1). They will soon find you, and if it’s not C.relictus it might be another of the Tabanidae.
A little etymology to finish. From Greek chrysōps gold-colored, from chrys- + ōps eye. Relictus seems to come from relic, being left behind or abandoned. though I’m not sure what this alludes to. Perhaps someone with more brains than I have can add something.
- Brock, P.D. (2014) A comprehensive Guide to Insects of Britain & Ireland. Pisces Publications.
- Naturespot.org.uk. Chrysops relictus. http://www.naturespot.org.uk/species/twin-lobed-deerfly. (Accessed 2017.06.25).
- Grayson, A. (1997). Personal notes on attacks by female tabanids. Larger Brachycera Recording Scheme Newsletter 15. http://www.brc.ac.uk/soldierflies-and-allies/sites/www.brc.ac.uk.soldierflies-and-allies/files/newsletter/Larger%20Brachycera%20newsletter%2015.pdf (accessed 2017.06.25).
- arrive.org. Chrysops relictus. http://www.arkive.org/horse-fly/chrysops-relictus/. (accessed 2017.06.25).
- Influentionpoints.com Chrysops relictus. http://influentialpoints.com/Gallery/Chrysops_relictus_Twin-lobed_deerfly.htm (Accessed 2017.05.25).
- NBN. Chrysops relictus. https://species.nbnatlas.org/species/NBNSYS0000007868. (Accessed 2017.05.25).