The drinks are on me

By Athayde Tonhasca

The broad-leaved helleborine (Epipactis helleborine) is found throughout UK and much of Europe and Asia in all sorts of habitats, including urban and disturbed areas. This orchid was introduced to America, where it is viewed as an invasive species in some places. Despite its common occurrence and being the source of a reasonable supply of nectar, the broad-leaved helleborine is often ignored by insects, a fact noted by Charles Darwin.

The orchid’s small, inconspicuous, greenish/purplish flowers are not exactly good marketing for attracting bees and other pollinators. But one group of insects are keen visitors: wasps, in particular the European (Vespula germanica) and the common wasp (V. vulgaris). 

A broad-leaved helleborine flower © Björn S., Wikipedia Creative Commons
A broad-leaved helleborine flower © Björn S., Wikipedia Creative Commons

Adult wasps feed mostly on carbohydrates, which they get from nectar – or from your sugary drink, if you give them a chance. But the nectar of broad-leaved helleborines is special: it’s laced with chemical compounds, some of them with narcotic properties. It also contains ethanol and other alcohols, possibly as the result of fermentation by yeasts and bacteria. This chemical cocktail is toxic or repellent to many visitors, but not to wasps: they lap it up. Unavoidably, a concoction of opioid and morphine derivatives plus alcohol, even in minute amounts, has consequences for its consumers. Wasps become intoxicated and sluggish after a few sips, which suits the orchid very well. They spend more time on the flower, staggering about and thus increasing their chances of ending up with a pollinium (a sticky mass of pollen grains) glued to their heads. Watch it. Nobody knows if wasps are hungover afterwards.

A wasp with pollinia attached to its face © Saarland, Wikipedia Creative Commons
A wasp with pollinia attached to its face © Saarland, Wikipedia Creative Commons

This orchid has another trick up its sleeve besides inebriating nectar; it also lures wasps with false promises of prey for their larvae. It turns out that these flowers release chemicals that mimic green-leaf volatiles, which are produced by plant tissues when they are damaged by herbivores. Wasps are attracted to green-leaf volatiles in the hope of finding some juicy caterpillars chomping on the host plant. When a wasp gets to the flower, its attention is diverted to the sugary nectar, so the scent scam is forgotten.

Orchids are highly diverse: with approximately 25,000 described species, they make up about 10% of all flowering plants. About one third of orchids do not offer food rewards – nectar or pollen – to visiting pollinators. Instead, they have evolved all sorts of tricks to attract insects. Some flowers have the shape, colours or scents of food-rewarding plants; they may bait male insects by resembling female counterparts, or by releasing pheromone mimics; sometimes they charm visitors that are seeking a place to lay their eggs. Or by using a combination of artifices, as it is the case of the broad-leaved helleborine.

These deceiving orchids attract only a handful of insects that respond to specific chemical or visual cues, so many potential pollinators are excluded. But the strategy pays. Pollen is transported more efficiently for deceptive species than for those with multiple pollinators. This means that more pollen is taken to another flower of the same species, and less is dropped or deposited on the wrong flower.

Deception works for orchids, but how about their cheated visitors? Sometimes they are rewarded, but often they get nothing. We don’t have much information about the insects’ side of this relationship. They must benefit somehow, or at the very least they are not significantly harmed. This matters to wasps, as they pollinate around 5 % of all known orchid species.

Orchids provoke much fascination for their biology, diversity and exoticism. This level of attention has helped us appreciate better the role of wasps. Most of them don’t collect pollen, and their lack of body hairs – compared to bees – does not allow for many pollen grains to attach to their bodies. But if we go by their contribution to orchids’ reproduction, these important but often maligned insects have much to reveal about their part in pollination services.

An European wasp, a frequently cheated pollinator © User:Fir0002, Wikipedia Creative Commons
An European wasp, a frequently cheated pollinator © User:Fir0002, Wikipedia Creative Commons

The unfairly maligned wasps

I saw a wasp upon a wall

And did not like his face at all:

And so the creature had no time

To wonder whether he liked mine.

‘Plain Murder’, A.G. Prys-Jones.


The common wasp (Vespula vulgaris) and its close relative, the German wasp (Vespula germanica), are not likely candidates for the most loved insects, but many people are not aware of their ecological value, writes Athayde Tonhasca.

Wasps feed mostly on high-energy sugars and carbohydrates from foods such as nectar and fruit. Because they are not covered with fuzzy hairs, wasps are much less efficient pollinators than bees. Even so, they are thought to be the main pollinators of ivy, which flowers late in the year when the number of bees diminishes and wasps require more nectar to produce males and queens. Because of their high energy content, ivy fruits are important for many farmland and garden birds, so wasps contribute to their food supply.

Wasps for Jim _m204018

Vespula sp. © Caroline Anderson

Adult wasps feed on sugars, but their larvae need protein. Adults provide it by hunting soft-bodied invertebrates such as caterpillars, flies, spiders and beetle larvae.

Researchers in New Zealand estimated that wasps capture ~0.8 to 4.8 million prey items per hectare per season (1.4 to 8.1 kg of prey/ha), which is equivalent to what is taken by all insectivorous birds in the same area. The figures for Britain are likely to be lower, but nonetheless it is evident that wasps are voracious predators, and thus gardeners’ allies.


A common wasp captures a horsefly.   © Robert Goossens, Wikipedia Creative Commons

Wasps may spoil your picnic, but without them, your hamper could have been deprived of bread, beer and wine. Yeast – especially Saccharomyces cerevisiae – has been fundamental to baking, brewing and winemaking throughout human history. In nature, yeast cells are found primarily on ripe fruits during the summer months. Since yeast is not airborne, it must rely on vectors to move from plant to plant. For years it has been assumed that birds or bees were responsible for transporting yeast cells, but nobody could explain how they survived the winter. Italian researchers suspected that wasps were involved, because they feed on yeast-harbouring grapes, and their nests are hibernation havens for microorganisms.

The research team analysed samples from vineyards around Italy to find several species and hundreds of strains of yeast in the wasps’ guts. Some were related to wine strains of S. cerevisiae, others were similar to bread strains. Also, yeast survived the winter in the insects’ guts, and was transferred to the larvae via the food regurgitated by the queen. Other organisms such as birds may be involved in the life cycle of yeasts, but wasps seem to be especially important.

Common Wasp nest

Common wasp nest © Richerman, Wikipedia Creative Commons

Wasps are also master engineers. They build their nest with a strong, lightweight and waterproof paper-like material produced by a mix of saliva and scrap wood, which is chewed to a pulp. The queen kick starts it by building a column and coating it with a chemical that repels ants. Then she builds cells around it, all in clusters of hexagonal units. Workers expand the nest by building more cells, ventilating them by vibrating their wings. The cells’ hexagonal configuration maximises strength and efficiency, as this design demands the least amount of energy and building material.

So next time someone asks you what’s the point of wasps, you can say they are fundamental for nature and for us, and they are fascinating creatures with complex social organisation and efficiency. They may be a nuisance now and then, but possible clashes with us are easily avoided.

Wasps are not aggressive outside the nest; when they hover persistently over your bottle of lemonade or sandwich, they are only interested in the food and will not deliberately attack you. The best strategy to avoid a close encounter is by minimizing the chances of attracting them. Do not leave food exposed; keep it in sealed containers and put away any rubbish into lidded bins. If a wasp flies towards your food, wait for it to fly away; flailing your arms increases the chances of entrapping the wasp, which could then sting you.

However, wasps will defend their nest aggressively if disturbed or threatened. If you find yourself near a nest, retreat without producing much vibration or noise. Take care with lawnmowers and other motorized equipment because they may trigger a defensive reaction.

All packed up for winter

“I’ll be back”.  It’s one of the most famous and most menacing lines in movie history.  Now, we can’t compare the return of the Terminator to the return of our pollinator trails, but the phrase is fairly appropriate.  This after all is the time of year when we pack up the signs and store them over winter, but come early next spring we dust them down and bring them out again. 

Staff at our reserves have been telling us how popular the information panels we produced for our pollinator trails have been.  Many, many visitors have lingered to take in the information on offer, and there is reason to suspect that it is the more ‘surprising’ panels that provoke most interest.  This was certainly the case of St Cyrus NNR where one of the most popular signs talked about wasps and how beneficial they can be. Busting that myth that wasps are ‘bad guys’ seemed to go down well.

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So where are our five trails lest you should be thinking come 2020 “I’m going to visit these”?


Top Major South America Commodities

Furthest north at the moment is our Forvie set of panels.  These are on a short trail immediately adjacent to the visitor centre to the north of the reserve. Topics covered included ‘What you can do to help pollinators’, a look at hoverflies, the red-tailed bumblebee, hibernation sites and the value to pollinators from mowing the grass less. The length of bees’ tongues gets an honourable mention too. With a lovely visitor centre to escape should the weather turn and superb sand dunes you would be hard pressed to get a more idyllic spot than Forvie to find out more about pollinators.

Image - Forvie Pollinator Trail 3 - July 2019

Having said that the staff who work at Creag Meagaidh would argue vehemently that their site is even better. With mountains, regenerating woodlands and a mosaic of marvellous habitats their’s is a reserve super-rich in diversity. It is also home to one of our pollinator trails and with a determination to provide hedgerows and wildflower meadows they certainly do their bit for pollinators here.

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Signs at Creag Meagaidh introduce information about the value of trees for bees, the role of wild roses and the power of flowers.  It’s a lovely mix of subjects that perfectly complements the amazing views this reserve is famed for. Be it the humble bumblebee or the mighty golden eagle this is a reserve that consistently captivates the visitor.

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Moving to the west coast and Taynish NNR offers up a very different experience.  Here oak woodlands, mosses, lichens, saltmarsh and shoreline jostle for attention. For pollinators the reserve offers a little bit of everything. As Caroline Anderson reported regularly in 2019 (complete with her amazing photographs) this is a reserve that pulls its weight when it comes to pollinator provision.

2019 Taynish Pollinator Trail - August - bee on purple loosestrife DSC_15461

Take a walk from the car park down to the mill and you will see pollinator signs revealing fascinating insights into mining bees, clearings and glades for butterflies and the value of some of our climbers.  It’s a lovely reserve, sweet with the smell of salt air, tranquil and yet very much alive with insect interest.

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The same can be said for Flanders Moss in Stirlingshire. The reserve is a sure fire spot to see lizards, and of late harriers have been catching the eye, but for pollinators it’s a bit of a haven too. The car park adjoins a prolific wildflower meadow, sown by local schoolchildren, and the swathe of willows along the path leading onto the boardwalk over ‘the moss’ are an early season bonus for so many pollinators.

Dave Pickett 2

A revealing insight into little-known buzz pollination is popular with visitors, as is a sign devoted to that firm Scottish favourite – heather.  For many children the lure of the viewing platform is a must, and reserve staff use the area at the foot of this panoramic feast to further engage with visitors through posters and factsheets.

2019 Taynish Pollinator Trail - August - red admiral on knapweed DSC_1856

We have pollinator trails at five fabulous reserves and the final piece in the quintet jigsaw is St Cyrus NNR.  Long before we even thought of a pollinator trail, this reserve had a flowery trail – so trails are nothing new to staff here. But with flowers you get pollinators and so the scene was nicely set to talk about our hard pressed pollinating insects.

Clustered Bellflower, St Cyrus NNR, Grampian area. ©Lorne Gill/SNH

The signs here include many of the signs mentioned at our other four reserves, but the ace up the sleeve of the staff at St Cyrus is their children’s activity quiz. Eagle eyed schoolchildren on a day-trip can win a prize by filling in their quiz sheets based on what they read on the signs here.

With prizes up for grabs we are probably back where we began. For surely nothing entices a visitor to utter that famous line of “I’ll be back” than the prospect of a prize … or maybe it’s the lure of the pollinators.  Either way our NNRs are must visit destinations for wildlife and people. And we have certainly saved a space for pollinators.

Photo - Knitted Bees - image for National Knitting Day - June 2019