Prehistoric

It's been perplexing me for a while now that, while I can always find leafhoppers when I do my garden mini-beast safaris, I'd never once spotted a planthopper. Today I broke my duck with three tiny (sub-3mm) Issus coleoptratus nymphs, which I beat from the ivy on our side fence - a warm and sheltered spot that I suspect will be providing a winter roost for a good number of invertebrates. Realising as soon as I looked at them closely that they were unwinged nymphs, I carefully returned them to the ivy after I'd photographed them, but in truth I probably needn't have bothered: even the fully-winged adults of this species are flightless, but they're superb jumpers and can probably put themselves exactly where they want to be without any clumsy interventions from me.

There's not much information about Issus coleoptratus on either British Bugs or NatureSpot, but there's a lot in this article, which was posted twelve years ago in Worcestershire Record, and it's from here I've learned that this species is markedly synanthropic - that is, it occurs in close proximity with humans - and that while it's usually said to breed on deciduous trees such as hazel, birch and oak, it's also strongly associated with ivy, and turns up on a number of garden shrubs such as Philadelphus and Choisya. The author, P.F. Whitehead, states that the nymphal stages of this bug (and the closely related, though rarer, Issus muscaeformis) are long-lived - that is, it moves only slowly through these stages towards adulthood - and that it overwinters at least once as a nymph. This is a little disappointing for me, because I'd been setting myself a mental alarm to go back to the ivy in a couple of weeks to try to find an adult, but if this author is correct it doesn't seem as though there's much point in trying for one before next year. Based on the structure of the wing buds, which are showing sensory pits rather than veins, I believe that this is a mid-instar nymph, and therefore it has at least two moults to undergo before it attains adulthood.

When R saw this photo his verdict was that the bug looked prehistoric, and I agree - though I also liked the description I saw in someone else's blog that it's a pretty Steampunk kind of creature. R particularly wanted to know why it looks as though it has a paintbrush protruding from it's bum, but beyond the fact that what looks like a tuft of hairy bristles is actually a clump of wax filaments, and that these are a typical feature of Issid nymphs, there's almost nothing written about them on line. So I'm grateful to Stewart Bevan from the Facebook UK Hemiptera group for providing the following information: "the protrusions are filaments of waxy material from the sugars/starches from the sap they feed on; the waste is expelled from the body as those abdominal filament structures." Unsurprisingly, the filaments are quite fragile: my second specimen had fewer than this, and some of them were protruding at odd angles, and in my third specimen they'd all been broken off and were short and uneven.

There was quite a scientific stir around Issus coleoptratus a few years ago when a paper appeared, describing a gearing system that locks its back legs together so that they work synchronously, stopping it spinning out of control when it springs. This is fascinating, but the headline "This Insect Has The Only Mechanical Gears Ever Found in Nature" is misleading: all planthopper nymphs appear to have this mechanism, which is replaced by a less exciting but more robust one at the final moult. The fact that a gearing system existed had been known for some time, but the experiments described in the 2013 paper were the first to prove how it worked. Despite the headline overstatement, I think the photos in the Smithsonian article are pretty cool.