Essays on Nature: September 2019

Green Shieldbug nymph

It’s been a busy month in the insect world as you would expect at this time of year and we’ve seen many new species – new as in insects we haven’t seen or noticed before. The hemiptera have been well represented – this group of insects, as the name suggests have half the wing membranous and the other half hard like a beetle. Shield bugs are typical hemiptera. We have seen Hairy Shield-bug, Green shieldbug and a Black-kneed capsid bug.

There have also been a couple of tiny ones that only have latin names so I won’t bore you with those. I found one hemipteran bug called an Ant Damsel bug which looks like an ant but isn't one that I didn’t know existed until I looked on a Facebook Group to identify the others.

The pond has attracted 5 species of dragonfly, and one or two emperor dragonfly females have been laying lots of eggs in the pond, so that bodes well for future years. The moth trap has given us at least 3 species that we’ve not seen before as well as a mayfly, an hemipteran bug and two new beetles.

Ant Damsel Bug nymph

Mayfly - Cloeon dipterum

Hairy Shield-bug nymph

The most interesting beetle was called a Hornet Rove Beetle. Rove beetles are the sort of radical wing of the beetle party and choose not to look like beetles at all. They don’t bother with wing cases to cover the whole of their abdomen and could easily be mistaken for an earwig. The wing cases are very short (typically less than a third of the length of the abdomen) so that the wings have to be folded up to fit into the small space. These obviously take longer to deploy than normal rigid wings which perhaps explains why rove beetles tend to run rather than take flight. Probably the best known type of rove beetle is called the Devil’s Coach Horse.

Devil's Coach Horse (Staphylinus olens) in threat pose

This is a fearsome looking insect with powerful mandibles and will raise its tail in a threatening scorpion-like manner should you approach it. If you ignore the threat it will give you a painful bite and probably emit a foul odour from the white scent glands on its tail.

The Hornet Rove Beetle is a similar looking insect – in fact, I thought it was a devil’s coach horse at first. It is however much broader and stockier than the devil’s coach horse and used to be very rare, but as hornets are extending their range, so are the hornet rove beetles. This is because the hornet rove beetle spends most of its time in hornet nests where they feed on the detritus inside the nest and are presumably tolerated by the hornets for providing this clean-up service. It is a strong flier with a keen sense of smell (which enables it to find hornet’s nests in the first place) and when it runs out of food in the hornet’s nest it can fly considerable distances in search of other insects and invertebrates. It does this extra-mural foraging at night which explains how it ended up in the moth trap.

And for those who think I don’t get out enough – I found a very interesting fly in Philippa’s garden. Whatever the bush is called that it was found on, it must be a very good nectar source because it had attracted a large number of flies. This particular fly is one of the picture-winged flies that often have interesting markings on their wings – in this case the wings were rather plain but it did have rather striking stripy red eyes. It goes by the catchy name of Physiphora alceae.