Following my discovery of the stunning Xylota sylvarum at the reservoir a week or so ago, today I found a second species of Xylota on the same sand stone wall. This is the smaller Xylota segnis. One of the ways you can identify this species from the other small Xylota is by the row of spines along the base of the hind femur, which fortunately are clearly visible in this photo.
The Xylota species are really interesting, they rarely come to flowers, and behave in a similar way to predatory Ectemnius wasps, running around and flying short distances with a darting kind of flight, sometimes apearing to chase other, smaller insects. Of course they also look a bit like Ectemnius wasps, and I wondered if their behaviour was part of the mimic or just coincidental, perhaps because the hoverfly itself is predatory. In fact the hoverfly is not predatory, it feeds on pollen which has fallen from flowers onto the leaves of plants, or in this case onto the wall (which was overhung by several tall species of plant).
Just to make them even more fascinating, apparently the further north you go the more likely they are to come to flowers, until by the time you get to Scotland they come to flowers with the same regularity as any other hoverfly species.
So it would appear perhaps that the wasp like behaviour is part of the mimic, though this is just speculation on my part.
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