One of the joys of having a patch of wildlife garden, even if it is small like ours, is sitting in the sun and watching the species that visit it. Often they are familiar - our pond attracts damselflies and dragoflies, and we try to include a wide range of pollinator-friendly plants for bees and hoverflies, but sometimes something a little different appears. In this case a little flicker of movement caught my eye and I looked closer to see two small flies waving their wings at each other. The wings had dark patterns of blotches and lines and I recognised them as being in the family Tephritidae. This family has no common name as such, but they are sometimes considered to be 'fruit flies' in the broad sense, and are also included in the informal grouping known as 'picture-winged flies'. A little more research in Smit (2010) and White (1988) confirmed the species as Tephritis neesii, which is common on Leucanthemum (e.g. ox-eye daisies as here) in southern England, where I live. So, nothing unusual as such, but I'd not seen it before; I did wonder if the 'dance' was a form of competition between males, but it is actually a male-female mating display.
Pair of Tephritis neesii during their mating dance.
It also turns out that in some tephritids, the form of the dance can indicate the genus of the fly - Tephritis such as these hold their wings flat and open/close them alternately; Urophora open/close them simultaneously while rocking from side to side; Chaetorella hold their wings sideways with the edge pointing up, then shake them. Males do fight, but it is less elegant - there was a third fly just out of shot that buzzed one of the pair later on. Though my photo shows the wing pattern quite clearly (it's the same in males and females), a video shows the dance itself, so here's one that's been kindly posted on YouTube:
References
Smit, J.T. (2010). De Nederlandse boorvliegen (Tephritidae). Entomologische Tabellen. Supplement bij Nederlandse Faunistische Mededelingen, 5: 1–159. [In Dutch]
White, I.M. (1988). Tephritid flies. Diptera: Tephritidae. Handbooks for the Identification of British Insects10(5a): 1–134.
Zebra spiders in the genus Salticus are a familiar sight in and around houses and other buildings in Britain and other parts of northern Europe, and their common name derives from their striped pattern.
Salticus scenicus, a common species near buildings.
As for other spiders in the family Salticidae ('jumping spiders'), the carapace ('head') is more-or-less squared off at the front with two large central eyes facing forward and two smaller ones at the corners (red lines in the image below). These are highly mobile with highly developed focusing mechanisms, and are able to see both colour and polarised light. Just behind these are two tiny side-facing eyes (green lines) and then two more small, but easier to see ones (blue lines); these smaller eyes mainly detect movement and the spider is likely to turn quickly towards a moving object to focus to larger eyes on it.
Eyes of S. scenicus
This arrangement gives good forward binocular vision, unsurprising as they hunt by leaping at prey rather than by using a web. Instead, they attach an anchor-line of silk to the surface it is on, then the rear two pairs of legs are drawn in before being rapidly extended by pumping body fluid into them. In side view, the importance of frontal vision is clear as the carapace is extended forwards to form a short rostrum protruding above the legs.
On the hunt: S. scenicus emerging from a hole in a 'bug hotel'. The large front-facing eyes can be clearly seen.
Although S. scenicus is the commonest species to be found near buildings, there are other species in this genus and it is worth checking for them. They can be separated looking at the epigyne (in females) or the palps (in males). The clear presence of a large palp used in reproduction shows this is a male and its shape (circled below) is typical of S. scenicus.
Male S. scenicus showing the shape of the palp.
Though fairly small (this one is 5-6mm long, excluding legs), 'jumping spiders' are highly active in warm conditions, and therefore often seen - they are worth looking out for and even if you are not a spider-fan, they can be highly charismatic little creatures.
