How heatwaves affect wasps and bees
Well June was fun, don’t get me wrong I love the warm, even the hot weather of our summer’s but those intense days when the thermometer climbs above 32 degrees become hard work, especially if you’re like me and occasionally you have to work inside someone’s loft.
Quite often the only way to tackle a wasp nest is by going up into the loft and getting right up close and personal with the nest, and if you’re especially unlucky that day, you may have to put on your wasp suit as well.
Wasp suits are like a great big baggy pair of overalls with a head and face screen, there’s an outer layer or covering, and then an inner string vest style layer to prevent wasp or hornet stings from penetrating the covering. It’s the equivalent on a hot day to locking yourself in the car with all the windows closed.
As I say, its fun on a hot day. But I can’t help noticing the change in behaviour of wasps when its scorching hot and so I’ve written this blog on the effects of heatwaves on wasps and, about bee’s; not because these are pests but because there are concerns for their survivability as we see a shift to a warmer climate.
How does a heatwave effect wasps?
Wasps really benefit from hot weather and when I say hot, up to around 30 degrees Celsius is regarded as hot; at this point they can fly faster and they can even soak up ultraviolet light from the sun and convert this to additional energy, its a bit like an electric bike, you can pedal it as fast as you can and then engage the battery to go even faster.
So, wasps really like it hot, but not super-hot, when the temperatures rise above 30 degrees, the colony starts to become heat stressed. Wasp nests are often built inside cavity walls and lofts and the raised temperatures start to become a hazard, inside the nest, workers will be cutting holes in the outer sheath to create more airflow but if its too hot, that isn’t going to work, so many of the individual wasps take on the role as fans.
They will gather around the entrance and flap their wings to create a flow of air into the inner workings of the nest to help keep the larvae cool.
All this activity means that the usual roles such as paper production to build the nest, and foraging for insects to feed to the larvae are forgotten about, and combined, this stress means a drop in egg production.
We know that the Queen wasp lays eggs, that’s her job if you like, and these will all become female workers, but those workers also lay their own eggs, and these will become the male wasps, whose job is to mate and renew the colonies DNA into the nest season.
The importance of wasp larvae inside the nest is down to the fact that they supply food to the workers; when fed a juicy chopped up caterpillar, the wasp will tickle the grub and as a reward for being fed, it will regurgitate a sweet sticky mass, and this is what the adult worker wasp eats.
It’s a very clever adaptation, the more the larvae get fed, the more food for those doing the feeding and so there becomes more wasps, which in turn gives rise to more eggs and then, yep you’ve guessed it, more wasps.
Its not only larvae vomit that wasps eat but they’ll also partial to a hit of sweet flower nectar, and in a heatwave, because egg production starts to drop as the wasps are all busy trying to prevent the colony from cooking, there’s little or no food for the wasps. No problem, they can just get some nectar?
But this is the problem in extremely hot conditions, many flowers will stop producing nectar, the ideal temperature range for nectar production is between 15 degrees centigrade and 25 degrees, pretty much what you’d expect from our average summer. But when we get to the current spike of temperatures, 30 degrees to 35, the water content of the syrup evaporates, and the flower dries out and therein lies the problem.
The adult wasps have run out of food; this is something that we see in the autumn when wasps start harassing people eating and drinking outside. They’re desperate for something liquid and sweet and unfortunately that’s things that we like such as, soft drinks, sweet foods, and for the ladies, perfume.
You can take steps to mitigate wasps pestering you like hanging up wasp lures; these are simple bags of a sweet solution with a narrow way in, it’s best to hang these away from where you want to sit as they attract wasps and hornets, but once they fly in, they can’t get out and eventually drown in the solution. Once the bag is either full of dead wasps or the solution has evaporated, you just throw the whole thing away.
As the temperatures continue to climb, the only relief that you’ll get from wasps is when it gets to 40 degrees Celsius, at that point wasps cannot fly and they will start to die off. Not much comfort when its that hot and you’re slowly melting into a human puddle but at least you won’t be bothered by wasps.
How does a heatwave effect bees?
I have mentioned bees in this blog, and this covers honeybees, bumblebees and solitary bees because these reoccurring heatwaves cause as much, or even more stress for bees than that experienced by the wasps.
Bees face the same problems as we found that the wasps face, the hotter it gets they’ll see a drop in egg production and face the same plight of starvation as the flowers dry out, but for bumblebees, those fat little bees that defy aerodynamics, having a furry body isn’t such a good idea.
Bumblebees are adapted for cold climates, and you’ll often see them flying around on a winter’s day, they can shiver their flight muscles which raises their body temperature and that’s why you’ll see them, but when it comes to heat, temperatures above 35 degrees become lethal. In fact, when it climbs above 28 degrees, they start becoming stressed focusing on keeping the nest cool and at 32 degrees, all flight activity ceases.
The same goes for honeybees, they need to keep the hive temperatures between 33 and 36 degrees and so heatwaves cause the same stresses, being found in larger colony numbers though does give honeybees some advantages. There are more bees to help fan cooler air into the colony, plus they will gather outside of the hive rather than inside to keep the internal temperatures down.
A heatwave doesn’t have to kill a bee, harm will be done and it’s the poor solitary bees that lose out due to heatwaves, solitary bees exist in two broad categories; mining, those that live in the soil and masonry that burrow into mortar and wood. As solitary bees they cannot rely on workers to fan cool air as they do not form a colony, the heat severely impacts the brood wherever it is laid.
The female bee lodges food provisions in each separate larval chamber, this is a mix of pollen and nectar and with the heat, this can dry out or take on bacterial growth that renders it inedible.
Solitary bees don’t look after their young, the eggs are laid by the female bee and then left to their own devices, when the larvae are exposed to high temperatures, the males will see a drop of sperm count meaning that many males, if they do manage to emerge, will be infertile.
Now bees really struggle with heat through a double whammy of exhaustion from trying to keep the colony cool and starvation as many flowers will stop producing nectar and pollen, whether bumblebees or honeybees they really have a hard time when temperatures climb above 30 degrees centigrade.
What can we do to help wasps and bees?
These heatwaves will become less extreme because, well for the simple reason that they will become our normal summer and if this is the case then our native pollinators will start to decline, bumblebees may become absent in the south of England which would be a terrible shame. I have already seen Mediterranean paper wasps in Wokingham, these are an invasive species that will do very well in a warmer climate, as with every aspect of climate change, there are winners and there are losers.
You can visit the Royal Horticultural Society’s website for advice on providing drought resistant bee friendly plants and you can also help right now by putting out wasp and bee watering stations. These are just a shallow dish partially filled with stones so that pollinators can safely land and not fall in and drown.
Share this post:
