Upper Duddon Hymenoptera (bees, wasps, ants and sawflies)

"UPPER DUDDON HYMENOPTERA" by Chris Arthur, ecologist and volunteer. April 2025.

Duddon Valley-based ecologist, and volunteer for Restoring Hardknott Forest, Chris Arthur, has been out and about in the valley recently, and offers some insights into the evolution and (sometimes weird) habits of what he's observed so far this year, with a focus on Hymenoptera. Follow his instagram account for more on invertebrates (but also bats, reptiles and more). His earlier blog on dragonflies and damselflies can be found here. All photos by Chris Arthur.

What are the Hymenoptera?

The Hymenoptera is a vast order of invertebrates that includes bees, wasps, ants and sawflies. The sawflies (Symphyta) are the oldest family of the order and are characterised by the ‘saws’ of the females which are used to slide open vegetation in which to lay their eggs. From these, the Apocrita evolved with the characteristic ‘wasp waist’ that defines this sub-order. First came the (sort-of) predatory wasps, then later, the bees which returned to vegetarianism (but not necessarily altruism!) and the ants (who unfairly do not feature again in this article, especially as the Hardknott staff love a hairy wood ant). *NB: We do love hairy wood ants, but only the appropriate amount*

Within these groupings and my questionable descriptions thereof, exists different life histories, interactions and dependencies. The typical life cycle involves females laying eggs which develop in larvae before undergoing complete metamorphosis to finally emerge as adults. Whilst all sawflies are solitary, and all ants form social colonies, bees and wasps can be either depending on the species (and in some cases climate and geography!). Whilst the social species such as honey bees and the ‘black and yellow stripey’ wasps are the most well-known, they are far outnumbered by their solitary counterparts. In the UK there is c.270 species of bee, with only the honeybee and 24 species of bumblebee showing social behaviour and over 9000 wasp species, the overwhelming majority of which are solitary. In most solitary bee or wasp species, nests are made in loose soil, masonry or holes in wood. Females lay single eggs in cells provisioned with a stockpile of food (pollen for bees, invertebrate prey for wasps) for the larvae to feed on once it hatches. Sawflies, in contrast, are left to fend for themselves and develop into caterpillar-esque larvae which can be found on vegetation.

Parasite vs parasitiod

But there are some significantly different life cycles.

I’m sure most people are familiar with the concept of a parasite, but a parasitOID is an organism that lives at the expense of its host, and that eventually results in its demise (which is not the case for a parasite). The most famous of these are the Ichneumonidae (ick-new-mon-id-ae) wasps which Charles Darwin famously attributed the existence of to his declining faith in a creator. The Ichneumonidae are an enormously species rich group that is severely under-studied, in part due to the difficulty in identifying the majority of species. The females lay eggs in living caterpillars, moth larvae, beetle larvae and other invertebrates which hatch and feed on their host, eating them alive. I’m increasingly interested in these wasps so anyone who finds one and is willing to collect them and pass them on to be identified, please let me know. Some species are nocturnal and frequently visit light traps for moths.

Kleptoparistism isn’t quite as macabre, but it isn’t far off. These organisms find the nests of other species and lay their own eggs inside. Once hatched, the larvae dispose of the host’s offspring and use the carefully provisioned stores of food. Sometimes these species can be quite generalist in targeting host nests, but there can also be very specific associations between host and kleptoparasite.

Local rarities

Last year two bee species were found around Wallabarrow that are considered nationally scarce and have suffered significant declines in recent decades. These are the diminutive Andrena coitana and its specialist kleptoparasite (now you know what that means after reading the lengthy intro!) Nomada obtusifrons. This latter bee has only been recorded in Cumbria once before in c.1800, but can be assumed to be under-recorded both in the county and nationally.

Further down the valley, another very rare bee was found – Osmia parietina. This wasn’t quite in the Upper Duddon area (it was actually my front garden), but its entirely plausible it will be found further up the valley. This species is only found in Northern and Western areas in the UK. It has been recorded elsewhere in Cumbria, but not in the Duddon valley before.

Also slightly South of the area (not my garden but along the road outside!) but a potential harbinger of colonisation was a single male European hornet (Vespa crabro) feeding on Ivy in the autumn. European hornets are gentle giants (and definitely not to be confused with Asian hornets, which you have basically zero chance of finding in Cumbria for the time being) and historically only a Southern species. They’ve been slowly spreading Northwards but there’s only 4 other records from the county with the nearest being Hay Bridge or Roudsea to the East. Hopefully this male didn’t come alone and we’ll soon see them regularly in the valley. Whilst they’re bigger than other social wasps, they’re generally more docile and not to be feared.

I’ve only picked out a few of the more notable Hymenoptera to talk about here but there is, of course, a wealth of species to be found in the valley. I hope it’s also clear that recording these species is incredibly important in understanding where they are found, and crucially, whether they are declining. For anyone interested in learning more, the Cumbria Biodiversity Data Centre has some info here which help explain the basics.