Originally published by Farming Future Food

Hoverflies are already well known to be farmers’ friends, providing natural pest control and pollination services, but research from Sweden suggests that they could also deliver beneficial microbes to help curb crop disease.

Swedish University of Agricultural Sciences experts tested whether Eupeodes corollae, a common European hoverfly species, could serve as what is known as an entomovector — an insect used in farming systems to move biological control products to where they are most needed.

Pollinators, predators…now entomovectors?

This ‘flying doctors’ approach has been successfully proven to work with bees, in particular bumblebees which are hairy and able to transport larger loads of pollen and other materials. Hoverflies, up to now, have been associated with the ecosystem services of pollination, being vital to yields for many crops, as well as preying on pests such as aphids and thrips.

The scientists tested E. corollae’s even broader potential in a strawberry cropping system, loading the hoverfly with a strain of the yeast Metschnikowia fructicola in an attempt to tackle grey mould, caused by the fungus Botrytis cinerea. Grey mould gets in strawberry flowers and affects the quality and longevity of post-harvest fruit.

Lab bench to polytunnel

They first showed in the lab that M. fructicola was an effective biological control agent against the mould, which can be a big problem with several different crops. Then they showed that the hoverflies could transport viable yeast from one dish to another.

Proof of concept complete, the scientists then used a polytunnel experiment with strawberry plants to assess how effectively the flies moved the yeast onto flowers (they could do it well). Finally, in a precision greenhouse facility, they assessed how effectively the technique controlled B. cinerea sprayed onto strawberry plants, compared to:

• Plants sprayed with the pathogen and yeast
• Hoverflies not vectoring the yeast and plants sprayed with pathogen
• Plants sprayed with just the pathogen
• Plants sprayed with water
• Untreated plants

Disease reduction, fruit quality boost

They found that the hoverfly vectoring brought results. Strawberries treated with the yeast-shifting hoverflies had the lowest signs of disease, reducing infection by 50–70% after the fruit had been two weeks in cold storage. The treatment also improved fruit shape and quality, highlighting the value of the insects’ pollination role. Hoverflies without the yeast also had a positive impact, second only to the vectoring hoverflies for reducing signs of disease and fruit quality.

Implications for integrated management

Dubbing the hoverflies “flying agents,” the scientists advocated for a hoverfly role in integrated pest and pollinator management (IPPM), a growing trend in protected crops which brings managed pollinators together with strategies to reduce pest pressure.

“This strategy supports the use of beneficial insect and microorganism species simultaneously in agroecosystems,” they wrote in Journal of Pest Science. “Moreover, this approach offers a sustainable alternative to application of chemical fungicides.”

The treatment didn’t affect survival of the flies used in the study, but the researchers called for further work exploring whether it might affect their fitness in other ways, as well an examination of how the technique affects the microbiome of flowers.

While the approach was studied in strawberry crops, it could also be extended to other crop systems, they suggested, underlining another area where future studies could be directed.

Key takeaways

• Hoverflies can deliver viable biological control microbes to crops.
• Vectoring yeast reduced strawberry grey mould by up to 70%.
• Hoverflies also improved fruit shape and overall quality.
• The approach offers an alternative to chemical fungicides.
• Technique could be extended beyond strawberries to other crops.

Hoverflies show potential as dual pollinators and disease-control agents was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

Dung beetles are ecologically vital — without them, animal excrement piles up, and nutrients cycle more slowly into ecosystems, with accumulative effects.

However, like many insect groups, they are under threat, facing alarming losses in areas where they were previously abundant. The reasons for dropping numbers are various, but livestock treatments aimed at tackling parasites and simply the decline of traditional grazing practices are major factors. As well as the decomposition decline, a loss of dung beetles hits other species, particularly predatory birds.

A rare long-term view

Improving conservation prospects requires long-term data sets, so the full picture can be understood. Yet for dung beetles there’s a distinct lack of this information. Enter Spanish researcher Jorge Lobo.

Lobo sampled 16 sites in a semi-arid region between Madrid and Toledo nine times over a period of 26 years, each time using five pitfall traps baited with sheep’s dung, placed five metres apart. Each sampling happened between the last week of May and first half of June, to ensure optimum warm and sunny conditions that would be suitable for most possible dung beetle species. He also recorded data on sheep flocks in the study areas, climate, changes in land use and distances from urban areas.

When sheep disappeared, beetles followed

His data analysis brought some sobering findings: a 50% overall decline in the number of dung beetle species, a 65% downturn in their abundance, with two-thirds of sites studied showing declines and three-quarters of the species.

What’s more, it all coincided with the loss of traditional sheep grazing in the region, which occurred after the first three sampling years. Beyond this pivotal point, five species of dung beetle from the Aphodiinae family, which are particularly dependent on fresh dung of a suitable size, were never seen again.

Stability after collapse

While it might be easy to predict a terminal decline towards a wipe out of most of these important beetles in the region, that hasn’t quite been the case.

On the sites with marked initial steep declines to low numbers, there followed a period of around 17 years where the beetle numbers tended to remain relatively stable. Sites further from urban areas barely saw the initial dips in beetle numbers. Further, the final sampling period recorded a bit of a rebound in populations of some beetle species.

Rabbits as an ecological stopgap

At first glance, this seems to make little sense. But this is where the wild rabbits come in. Their populations have remained relatively stable over the years, without too many disease threats and relatively unaffected by the degrading habitat. And while rabbit poo falls short of the density and volume of that produced by sheep, it’s enough to give beleaguered dung beetle populations something to work with and so hang on in there. Deer and wild boar may also offer some supportive dung, though this wasn’t quantified in the study.

The sites further from towns and cities had higher initial amounts of rabbits, meaning considerable poo was there as a backup plan for the beetles at the point when the sheep left. As for the species on the up at the end of the study period, there were three: Onthophagus merdarius, O. latigena and Aphodius foetidus. Lobo suggested that this could be due to climate fluctuations, or simply higher ecological adaptability in those beetles.

If wild rabbits are indeed the beetles’ flimsy lifeline, the problem is that there is evidence that they too are on the decline, in Spain and elsewhere — less a species to be badged ‘least concern’, more like ‘threatened’, say some. All the same, there is likely to be little appetite to add them as a conservation priority due to the influence of farmers and hunters.

Witnessing decline in a human-shaped landscape

Beyond a simple entomological study, the work painted a profound picture of how humans are affecting habitats. While some of the land which used to be grazed got on with an ad-hoc form of ‘rewilding’, the main change was man-made developments like houses and industry increasing by 145% in the studied area over the years.

By the end of his research write-up in Journal of Animal Ecology, Lobo cuts rather the philosophical figure, lamenting:

“Studies like this provide empirical evidence on how biological assemblages are responding to rapid environmental changes driven by human activity. In this context, the role of biologists becomes akin to that of notaries witnessing a world in decline.”

He does, however, find reason to finish on a more optimistic note, noting that the research does show the potential for wild mammal populations to recover after livestock has gone, buffering the decline of dung beetles. Signs that if given chance, new ecological connections can respond to our neglect and excess.

Key takeaways:

• Dung beetle species richness fell by 50% over 26 years in central Spain.
• Loss of traditional sheep grazing coincided with the steepest beetle declines.
• Some beetle populations stabilised after collapse rather than continuing to decline.
• Wild rabbits likely buffered beetle losses by providing alternative dung resources.
• Urban expansion dominated land-use change across the study area.

Dung beetles’ rabbit rescue? Bunny poo can prevent species declines becoming terminal was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

Originally published by Farming Future Food

Yeast can be transformed into a next generation pesticide and combined with sugary lure to kill spotted wing drosophila (Drosophila suzukii or SWD), an invasive fruit fly posing a major threat to soft fruit farming.

Invaded regions such as Europe have seen significant damage from SWD, which are native to Asia and difficult to control using current pest control methods. This has prompted considerable research exploring more potent alternatives.

Scientists from the Eck Institute for Global Health in Indiana have found that using RNA interference (RNAi), a process which introduces tiny RNA molecules into a cell, can silence what is known as the Shaker gene in the flies, causing neurological damage and death.

Turning baker’s yeast into a RNAi biopesticide

The researchers used a genetic engineering approach to make baker’s yeast (Saccharomyces cerevisiae) express a heat-inactivated biological pesticide which delivers the RNAi. In their latest research, they saw that making a paste using the yeast and a sugar bait, in this case flat Coca-Cola, can attract the pest flies, successfully controlling their populations under semi-field conditions.

They modified a soda bottle to continuously deliver Coke throughout the study. After initially feeding SWD in cages with their yeast-soda mix, they went on to release 50 flies in a free-standing mosquito net to test the approach over a six-day study. They also fed three species of mosquito and the related fruit fly Drosophila melanogaster the novel pesticide to test how specific it was to SWD.

Specificity and safety

The technique killed 96% of the SWD in the study, and critically, in their tests on the non-target insects, all of them survived. The researchers suggested that this because the target site of the RNAi is not present in the mosquitoes, and while even though it is present in D. melanogaster, the gene-silencing effects of RNAi don’t spread system-wide in the species.

Additional work will test the effectiveness of their pop-based lure in the field, while also assessing the ideal locations for bait stations.

“Although further evaluation of the RNAi yeast attractive targeted sugar bait feeders in the field is needed, RNAi yeasts targeting SWD may represent a new class of effective, yet biorational insecticides that can be used in integrated pest management programs for control of this destructive insect pest,” the researchers wrote in Pest Management Science.

From proof-of-concept to practice

Such pest management regimes may involve combining the sugar baits with pheromones, using them alongside SWD repellents as part of a push-pull control strategy or even developing a sprayable formulation of the novel pesticide.

Despite the promise, to employ such a technology commercially, there would be regulatory hurdles to overcome, the scientists conceded. This is because the DNA molecules used in the work have an antibiotic resistance marker, making it likely to fall foul of regulatory bodies. A move to a different yeast strain may be necessary, which has components necessary for RNAi success integrated into its genome. Such a yeast strain should also be more suitable for large-scale fermentation, they suggested.

Key takeaways

• RNAi yeast killed 96% of spotted wing drosophila in semi-field trials.
• The biopesticide targets a neurological gene essential to the pest’s survival.
• Sugar bait significantly improved attraction and control effectiveness.
• Non-target insects were unaffected in laboratory tests.
• Regulatory and scale-up challenges remain before field deployment.

Next-generation biopesticide uses RNAi yeast and a dash of Coca-Cola to target fruit fly pest was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

Jumping spiders are well known as the cutest spiders out there, spawning memes, adoring Reddit groups and a massive increase in their popularity as pets. But it’s time to look beyond the aesthetics and think about their ecology for once.

Like all spiders, they have great potential as pest-hunting friends of humanity, reducing populations of disease-spreading or generally undesirable bugs in the environment around us. But they do tend to be pretty tiny, so may be underestimated in their ability to affect matters at an ecosystem level.

Testing spider impact in a dengue hotspot

Brazilian researchers put their fawning over clusters of attentive arachnid eyes aside to check in on the predatory impact of jumping spiders in Uberlandia, a fast-growing city in the country. They wanted to know whether they were making any inroads into populations of the notorious disease-vectoring mosquito Aedes aegypti, and what that might mean for the incidence of dengue, a viral infection that can cause serious illness and even death in some cases.

In both a wet and dry season, they collected spiders from three districts with high recent incidence of dengue and three with low incidence, visually searching in 50 100-metre zones, while recording the abundance of A. aegypti eggs in special traps designed to attract females to lay. They also used an approach called stable isotope analysis to analyse the diet of the most found jumping spider species, the grey wall jumper (Menemerus bivittatus), to make sure that it was actually chowing down on the target mosquito.

Where spiders thrive, dengue is lower

They found that A. aegypti and the three species of jumping spiders they recorded tended to cross paths both in wet and dry seasons, and that spiders were in greater density in areas with low dengue incidence. Where there weren’t many spiders, there were more mosquito eggs. These findings are probably not unconnected, either, given that M. bivittatus’ bodily contents revealed that the mosquito is indeed part of its diet.

While acknowledging that many other factors certainly affect the presence of A. aegypti and the prevalence of dengue, the researchers are confident enough to suggest that jumping spiders are a control agent of the pest. Some species play more of a role than others, however.

Not all spiders are equal mosquito hunters

The grey wall jumper seems to be not only the one most seen in the study, but also the most likely to do damage to the disease-spreaders.

It is an urban-adapted species with a broad diet that has been shown to successfully hunt flies, while the other two species caught in the study, Corythalia conferta and Hasarius adansoni, tend towards ants as a preferred meal and forage close to their small shelters. This limits their possible interactions with mosquitoes, and as such, their potential as a human-helpful killer.

Biodiversity as a quiet public health ally

This may not be the last deep dive into the shadowy world of Brazilian spider-on-mosquito action. The scientists also mooted plans to look further at the whole community of spiders associated with human settlements, not just the exceptionally cute ones, and its impact on mosquito control, while trying to point to particular urban landscape features that encourage their thriving.

In answer the question posed at the top of this page, our diminutive spider friends are probably not going to be the leading destructive force against mosquitoes and the diseases they can spread, but they’re certainly a notable participant. Further evidence, if it were needed, of the fundamental importance of biodiversity in maintaining nature’s vital checks and balances — and keeping humans healthy.

Five key takeaways:

• Jumping spiders commonly overlap with dengue-carrying mosquitoes in urban Brazilian environments.
• Areas with more jumping spiders had fewer mosquito eggs and lower dengue incidence.
• Stable isotope analysis confirmed mosquitoes form part of the grey wall jumper’s diet.
• Urban-adapted spider species appear more effective mosquito predators than shelter-bound species.
• Spiders alone won’t stop dengue, but biodiversity can help suppress disease vectors.

Could the world’s cutest spiders aid the fight against a tropical disease? was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

It would be an understatement to suggest that insects have an image problem, and it’s one that has serious consequences: for one, people sadly see them as less worthy of conservation efforts.

As frustrating as peoples’ often knee-jerk responses to insects are to those like me who love them, it’s quite hard-wired stuff; threat responses from the age of early humanity when making snap decisions on what could harm you were a matter of survival. It must be added, of course, that things aren’t helped by the constant barrage of negative and largely misinformed media tropes about ‘killer’ insects out to get us.

When a body shape looks like a threat

Research over the years has added nuance to insect fear and antipathy — with the latest addition to this field a particularly striking one. It seems that resembling equipment that could deliver an injection is a big problem for a lot of bugs.

A team in Slovakia carried out a study with 654 students, showing them pictures of insects, 10 of which had sharp or needle-like appendages and 10 that didn’t, as well as the easily recognised stinging insects the European wasp (Vespula Germanica) and honeybee (Apis mellifera). They asked the participants to score the insects on a five-point scale according to their fear of being stung, attractiveness, willingness to protect and disgust.

They discovered a correlation between fear of being stung and fear of injections, suggesting that having previous traumatic experiences with injections can amplify the fear of insects. Fear of injections brought increased levels disgust and reduced perceptions of the insects’ attractiveness.

Fear of stings — even when there is no sting

There was little difference in the fear of being stung whether an insect shown was able to deliver a sting or just had body parts that looked like it might be able to.

As well as building on studies which showed people in India viewed a butterfly with long ‘tails’ as harmful and frightening and that people are generally not fans of ichneumon wasps and their huge (but harmless to us) ovipositors, such findings also echoed previous work with plants. Prior work had found that people were less willing to protect species with spines — again tapping into that deep-rooted fear of angular shapes that could pose a threat.

Bees, beauty and biological value

When looking at the overall picture, there were some seemingly contradictory results: participants were no more or less willing to protect an insect whether it looked harmful, was harmful or was harmless, partly because the well understood ecological value of bees offset the fear of being stung. Stinging insects, with their bright colours and stripes, were also considered more attractive and less disgusting then the harmful-looking and harmless insects.

Superficially, maybe the biggest contradiction of all was that while females showed higher levels of fear and disgust, they were also more willing to protect insects. But this probably reflects the fact that females have been found to be generally more conservation inclined, a philosophy that may help to override underlying facets of threat perception.

Choose your champions carefully

Neat findings, but to what ends? Well, the researchers reckon that it’s all food for thought for those selecting species to be the high-profile, charismatic species at the forefront of conservation or simply public relations initiatives. Species that they look like they might be about to give you a jab — as well as the particularly large ones — should be judiciously featured and properly contextualised to avoid inadvertently triggering deep-rooted responses.

Shaping attitudes early to prevent ‘biophobia’

That the participants of the study were aged 10–19 years was no accident. Bad experiences with both injections and insects can shape lifelong beliefs, especially when then growing up with unrealistic media portrayals and fearful parents that can lead to pronounced ‘biophobia’. There’s evidence of a growing trend to step away from nature in fear, so getting early interventions right could help shape a future with more realistic perceptions of, and harmonious interactions with, the non-human world.

Key takeaways:

• Needle-like insect features trigger fear and disgust, even when the species is harmless.
• Fear of injections strongly predicts fear of insects that appear capable of stinging.
• Visual threat cues matter more than actual ability to sting in shaping public attitudes.
• Bees’ familiarity and ecological value can override fear and increase willingness to protect them.
• Early negative experiences with insects can fuel lifelong fear and disengagement from nature.

Looking like a needle proves a jab against insect-positivity was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

This page is proudly invertebrate-biased but will happily give credit to the vertebrates where it’s due. With that in mind, let’s salute the beaver: supreme pollinator habitat creator.

It’s well-known that beavers are astute ecosystem architects, second only to humans in fact. They create dams and canals, fell trees and graze on vegetation, having profound knock-on effects whether they’ve been around an area forever or reintroduced as part of rewilding schemes.

Wild wetlands versus human ponds

Researchers at the University of Stirling set out to explore the differences brought about by beaver-moulded wetlands and man-made ponds, looking at plants, pollinators and the networks between the two. Their study area was in eastern Scotland, where they surveyed six wetlands, three of which were created by beavers and three artificially built.

In Journal of Applied Ecology, they reported that beaver wetlands had 29% more hoverfly species and increased numbers of hoverflies and butterflies by 119% and 45%, respectively, when compared to the human habitat creation efforts. There were no significant differences between the habitat types in numbers or species richness of bees and moths, however, highlighting that human-constructed ponds also have their place in creating habitat for important pollinators.

The team recorded similar numbers of plant species for each wetland type. There were crossovers between the two, with different types of indicator species — plants which reveal the health of the environment — present. In the beaver wetlands, such species were generally focused on growth in the disturbed environment, whereas in the human-mad ponds, the indicators were mainly those tolerant to stress. The number of interactions between plants and their pollinators were 31% lower around the ponds than in the beaver wetlands, with hoverfly interactions unsurprisingly dominating in the beaver-moulded ecosystems.

Hoverflies steal the spotlight

More attention is being paid to the importance of hoverflies as pollinators than ever, so news of beavers’ impact on their presence will likely spark excited conversations between conservationists focused on both beavers and syrphids. And while butterflies are enduringly popular with the public, more than half of UK butterflies look to be in long-term decline — not a unique trend when looking at the global picture.

Beaver habitats for farming landscapes

Whether through formal releases or more ad-hoc efforts, wild beavers are breeding on nine rivers in the UK, with more reintroductions being considered. On the back of the work, the researchers are calling for beaver wetlands to be included as part of agri-environment schemes, in which farmers are subsidised to support biodiversity efforts in agricultural landscapes.

There is certainly a logic there, given recorded declines in pollinating insects, vital to agricultural yields. But as the scientists behind the work point out, while there has been financial support for ponds built by humans on farmland, there has been nothing to date to help farmers accommodate beaver wetlands on their property.

Will this work be enough to change this, and perhaps more importantly, is this even what farmers want? Beavers remain a touchy topic, but an increased evidence base for their positive impact alongside growing knowledge on how food production and beavers can coexist will no doubt help.

There’s also a wider point here: while wetlands are often feted for their impacts on birds, plant and amphibians, much less has been said about what they can do for pollinators. It’s becoming clearer than ever that restoring biodiversity, and the ecosystem services it brings, rests at least in part on letting go of our need to strictly control water. All the same, more human-built ponds don’t hurt, either.

Key takeaways:

• Beaver-made wetlands host far more hoverfly species and higher butterfly numbers than human ponds.
• Plant diversity was similar, but ecological indicator species differed between wetland types.
• Pollinator–plant interactions were 31% higher in beaver wetlands, dominated by hoverflies.
• Researchers urge agri-environment schemes to support beaver wetlands on farmland.
• Evidence suggests beavers aid biodiversity, but farmer acceptance remains a key barrier.

Where beavers return, pollinators follow: the quiet power of wild wetlands was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

Non-native insect species have a bad rep; particularly the sneaky ones that nobody notices until they’re already established across swathes of a continent.

An insect to help change that narrative could be an as-yet unidentified East Asian parasitoid wasp from the genus Eriborus, which has shown up in Switzerland and Germany.

It probably got there by hitching a ride on an imported box tree (Buxus spp.) — a crucial detail, as Eriborus is known to parasitise the box moth (Cydalima perspectalis), one of Europe’s most notorious invasive species.

Box trees under siege

The pest moth arrived by the same route, on trees imported from its native South Korea. Since it hit Europe in 2007, it has swept across much of the continent, free from the natural enemies of its home range and defoliating box trees almost at will. Without intervention, box, a popular feature of ornamental gardens and a favourite material of woodworkers, looked to be on its way to an ecological extinction.

As an indication of the level of panic induced by the invader among groundskeepers at some of the UK’s most manicured gardens, box moth pheromone traps were by far the most ordered product during a spell I spent working for a UK sustainable pest control company. The traps are good at telling you the moths are there, but nowhere near enough to stop them breeding and feasting.

Enter Eriborus, and the promise of turning the tide.

The wasp’s quiet revenge

From its beginnings in a botanical garden in Basel, scientists from the international research organisation CABI found it to be well established in gardens and wild stands of box trees. To see whether it was making any inroads into the moths, they collected moth caterpillars from 13 sites in affected regions, to see what they developed into under lab conditions. Would they be looking at lots of healthy moth pupae or the cocoons of their enemy?

They found high parasitism of box moth caterpillars among wild box, of 68% and 32% and a lesser rate among box planted in gardens, where it was between 6 and 19%. Not numbers to end the box moth saga entirely, but it’s a good contribution.

Eriborus is not the only potential moth-tamer discovered as part of the work. On a site where none of the wasp were found, an unidentified parasitic fly had been having a go. In less positive news, they also found a couple of examples of a hyperparasitoid — a wasp that targets the young of parasitoid wasps. There are always layers of destruction to consider where insects are involved, and in both cases, these were likely to be local species developing a taste for the invaders.

Accidental release or lucky break?

As it happens, Eriborus was being considering as a potential candidate for release in Europe, as a last-ditch biological option to rescue Buxus from its seemingly inevitable fate. The possibility was even considered that it could have originated from a CABI quarantine facility.

The dates didn’t tally with its life cycle, however, meaning this is almost certainly a truly happy accident than a serendipitous oops.

What happens next for Europe’s box trees

What’s certain is that the wasp’s establishment in the heart of Europe makes it much easier to consider artificially increasing its number — but there are remaining unknowns, the most important being just how specific its tastes are.

Further research will establish the extent it is parasitising local moth species as well as the unwanted outsider, and whether this is level that could be lived with as part of any efforts to increase its number. It’s also possible that Eriborus is established well beyond Switzerland and Germany, but that too is work for another day.

Biological control is rarely simple, so there may be some way to go before we truly know what the arrival of an accidental hero can do to halt the box moth’s trend of tree annihilation. All the same, it’s a welcome sliver of light for ornamental hedge trimmers and traditional craftsfolk.

Key takeaways:

• An East Asian wasp, Eriborus, emerged in Switzerland and Germany, likely via imported box trees.
• The wasp parasitises box moth caterpillars, which have ravaged European gardens since 2007.
• Field studies found up to 68% parasitism in wild box populations — a major natural boost.
• Its arrival was accidental, not lab-linked, but could still aid future biological control efforts.
• Scientists must confirm the wasp’s host specificity before supporting intentional releases across Europe.

Europe’s beleaguered box trees could have an accidental saviour was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.

The effects of climate change on insects are many, but the scientific community has invariably focused on the direct ones: mortality and impacts on physiological characteristics such as body size.

Heatwaves hit insect behaviour

Beneath the killer blows, there are a raft of indirect effects that can work to erode the ability of species to successfully carry out their lives. One that’s certainly under-explored is what it’s doing to their sex lives. Researchers in Australia have addressed this omission.

There was some previous research to work from, which had shown that mating signals, sperm production and female interest in getting jiggy could be reduced in insects by exposure to extreme temperatures over several days.

Fieldwork in natural conditions

However, these were often lab studies using temperature controls; the team at Macquarie University wanted to know what was going on under natural conditions, and specifically to the red and blue damsel (Xanthagrion erythroneurum), which perhaps unsurprisingly is a type of damselfly.

To establish just to what extent temperature extremes were affecting their species of choice, the researchers used a tried and tested technique: simply going to a pond and recording what the damselflies were up to — albeit with some tweaks to make the observations scientifically valid.

They looked at abundance of the species, the number of flights they took, and crucially, the amount of mating going at the university pond. They monitored both during heatwaves — three days or more exceeding average temperatures for the time of year — and non-heatwave periods and marked and re-released insects to make sure they weren’t doing any double-counting.

Less love in the heat

They found that there was a drop in the number of mating pairs during heatwaves, suggesting that it was probably down to the females of the species not feeling it, seeking shaded areas to reduce their energy needs.

What they didn’t find was a reduction in the number of flights by damselflies or numbers of individuals in the area. So, how are they avoiding these impacts?

Shade-seeking survival tactics

Firstly, damselfly physiology and behaviour make for some heat mitigation, by reducing basking and positioning wings. The unexpectedly high amount of flying could be simply because they had to: more time needed to find mates and shade, plus the damselfly hustle to maintain territory and eat everything possible never stops. It’s also possible that flight can actively mitigate the effects of heat.

As far as the local numbers of individuals went, it’s likely that they were able to remain in the area by adaptive behaviours like moving to those shady areas and nearer the water, keeping their body temperatures within critical limits.

Long-term reproductive risks

That’s all well and good in the short term, but reduced mating is never a good sign for longer-term prospects, especially when aquatic insects like damselflies are also pressured by pollution and microplastics.

Increased frequency of heatwaves could well hurt damselfly populations in the long run, and if the findings are indicative of potential reproductive impacts to insects, there are likely to be many more species which are hit as severely, if not more. This would especially apply to those less able to make those short-term adaptions to extreme conditions than the nimble damselfly.

For the real connoisseurs of insect amour, you can enjoy previous posts about sexual sneaks, randy bees and mixed-up genes and sex mobs in the sky. You’ve got to give the people what they want.

Key takeaways:

• Heatwaves reduce damselfly mating rates.
• Females seek shade to save energy.
• Flight activity remains surprisingly high.
• Behavioural adaptation offers short-term relief.
• Reproductive decline threatens insect populations long-term.

Heatwaves dampen damselfly sex lives was originally published in Insects and That on Medium, where people are continuing the conversation by highlighting and responding to this story.