Two new flea beetles

I managed a brief walk this afternoon with my younger son at a site in south-east Cambridge. We didn't get long before the much needed rain began but I did managed to do a little bit of tapping vegetation over my white umbrella to see what beetles I could find.

I targeted clumps of plant that I couldn't for the life of me identify. When I was about 10 or 11 I was really into plants and spent lots of time IDing and drawing them. I used to go on trips with the local wildlife trust to see various interesting habitats and their plant assemblages. Unfortunately birds and moths quickly took over and my plant knowledge gradually faded and I've been trying (mainly unsuccessfully) to resurrect it over recent years. I was pretty sure it was in the borage family but didn't get beyond that.

Anyway, here's a crap photo of the plant

So it turns out it's Common Gromwell. The reason I was keen to know was that every patch I tapped had two species of Longitarsus flea beetle on it, and some species are host specific making it possible to narrow down the species.

First up was this one. I rarely find these an easy group and there are also some species that are rather catholic in their tastes and can turn up on a wide variety of plants. This individual was 2.4mm and was mainly yellow with black femora (slightly redder below) and a very thin and slightly darker sutural stripe.

For this group, the clincher is more often than not the aedeagus. I found a male and whipped one out. I struggled with the line drawings in Duff volume 4 but remembered that there's a rather good Polish site with lots of images. Sod's law it was down when I tried to access it. It eventually came online and then through a combination of the keys and picture matching I am pretty confident that this is Longitarsus exsoletus. A borage family feeder too. Although further confusion arose as NBN calls it L. exoletus - no S!

The clincher. L. exsoletus naughty bits.

I then decided to tackle the other species which was a touch smaller at 2mm.

Another dissected male and a bit of keying and more picture matching got this one to Longitarsus anchusae, another borage family feeder. I'm fairly confident on the ID but would be good to double check against specimens at some point.

Anyway, 2 new species for the beetle list. 💪