Firebugs

For the last three weeks, at the entrance to my old allotment site, some remarkably bright bugs have been hanging around.

These bugs are common in Europe but were first seen in Dovercourt, near Harwich, only in 2019. Somehow – even though they cannot fly – they have arrived in Colchester.

They are the Firebug Pyrrhocoris apterus, known to form large aggregations in warm places.

They were right by the path off Drury Road on the garden wall of the house on the right; also on the vegetation along its base and even on the black dustbin.

The largest aggregation was at the base of the nearest lime tree. This is no coincidence because these bugs feed on lime tree seeds, but more of that later.

These adult Firebugs were born last year and came out of hibernation sometime in March. They are now at their reproductive phase, which will last quite a while and after that they will die-off. Their life cycle lasts one year.

So right now quite a few adults are busy mating; they mate back-to-back, called tandems. They may stay in tandem for a very long time, this is probably a male guarding strategy.

Soon the females will lay their first batch of eggs. When the eggs hatch, the nymphs will feed on the nearby lime tree seeds by piercing them with their specialised mouth parts, the rostrum (beak), which functions as a piercing and sucking device.

Firebug nymphs are bright red and look like a miniature adult. Bugs (Hemiptera) do not undergo complete metamorphosis, unlike other insects which go from egg, larva, pupa, adult. Firebug nymphs moult several times before they reach adulthood sometime in the summer.

Then these adults will overwinter on the area or, in some cases, might reproduce again. Who knows? The answer to that is to watch them throughout the summer.

In any case, you can rest assured that Firebugs will not damage any crops in the allotment or nearby gardens because they are specialist seed feeders, lime trees and mallows - both belong to the same family, Malvacae. Formally lime trees used to belong to their own family, Tiliaceae, but after recent genetic studies they are now together placed with the mallows. Somehow Firebugs knew about it all along…

When these Firebugs turned up at this site is a bit of a mystery. They are widespread in the continent and elsewhere, but in Britain historically they were known only from one islet off Devon. Things changed since their recent sightings in North-East Essex in Dovercourt, September 2019, probably after their arrival as stowaways in Harwich’s port.

Since then they seem to be expanding extremely fast along the coast and even inland. I saw my first firebugs in Colchester in May 2022, in Abbeyfields, North Circular Rd, just a mating couple - lots of lime trees in that area.

Two years later, May 2024, Ashley Ford alerted me to this population at the entrance to the Drury Road Allotment site: a sizeable colony in a patch of land with 5 lime trees. So they must have been there at least the year before.

The trouble is, Firebugs, as their name Pyrrhocoris apterus implies, are supposed to be flightless (apterus means without wings). But things aren’t so simple.

They have two morphs: one with non-functional soft-wings, brachypterous or short-winged, and another with soft-wings, macropterous or macropters. In the vast literature about Firebugs, the consensus is that macropters do not fly, instead the females walk faster; their range is 200m. But this would not explain their rapid expansion since their arrival in Harwich.

Lots to find out. Right now it is well worth to keep a watch on this population and look out for them in other places near lime tres or mallows Please keep me posted.

Meanwhile let’s enjoy their colourful presence at a time when so much wildlife is in decline.

Acknowledgements:

I wish to thank Ashley Ford for alerting me to the Drury Rd population and Yvonne couch for helpful discussion.

A few references:

Couch, Y., 2022. Rearing Spurge Bugs and Firebugs, 2022. Essex Naturalist (New Series) 39: 259-263.

Gardiner, T. & Scarfe, L., 2020. Firebug Pyrrhocoris apterus (Hemiptera: Pyrrhocoridae) distribution in Harwich. Essex Naturalist (New Series) 37: 141-144.

Gibson, C. & Gibson, J., 2020. Two new bugs for Essex: Eurydema ornata and Pyrrhocoris apterus. Essex Naturalist (New Series) 37: 137-140.

Honěk, A., Martinková, Z. and Brabec, M., 2019. Mating activity of Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae) in nature. European Journal of Entomology, 116, pp.187-193. [PDF]

Hunter, K., 2020. Firebugs found at Two Tree Island. Essex Naturalist (New Series) 37: 146-146.

Kristenova, M., Exnerova, A. and ŠTYS, P., 2011. Seed preferences of Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae): Are there specialized trophic populations?. European Journal of Entomology, 108(4). [PDF]

Socha, R. and Zemek, R., 2003. Wing morph‐related differences in the walking pattern and dispersal in a flightless bug, Pyrrhocoris apterus (Heteroptera). Oikos, 100(1), pp.35-42. [PDF]