When a human looks at a distant skyscraper, it appears small to the eye. It’s a visual illusion, and we use other contextual information to know the building is actually tall.
Our new study shows, for the first time, that honeybees see size-based visual illusions too. Whether a size illusion is seen, or not, depends on how a target object is viewed.
These new results help us understand how visual illusions evolved in different species over time.
How humans experience illusions
Humans see lots of different illusions such as mirages, illusions of shape, length, size, and even colour (remember that dress?).
Visual illusions are errors in your own perception which can allow you to process the very complex visual information you see more easily.
One of the strongest geometric illusions we humans see is an illusion of size, called the Ebbinghaus Illusion.
Interestingly, species such as bottlenose dolphins, bower birds, domestic chicks, and redtail splitfins see this illusion in the same way as humans. However, animals such pigeons, domestic dogs, and bantams see the opposite illusion to what we see, and baboons do not see an illusion at all.
To understand why different species see size illusions in such different ways, and how an insect with a miniature brain might view a size illusion, we developed an experimental design using honeybees.
Why do animals perceive illusions differently?
It’s intriguing that some species view size illusions the same way as us, and some animals do not. Why is it that a baboon does not see any illusion when looking at the Ebbinghaus Illusion? Why do pigeons and dogs see the opposite illusion to us? Our team decided to look into the methodology of the past studies that had shown these differences.
When baboons, pigeons, dogs, and bantams were tested, they were looking at the illusion from either a set distance or from a forced close-range distance. For example, dogs had to touch the correct option with their noses, and birds had to peck the correct option meaning these species were viewing the illusion at a very close distance. Baboons, on the other hand, were viewing the illusion at a set distance, unable to move closer than a certain distance from a screen that presented the illusionary pictures.
With this knowledge, we decided to test honeybees using two study conditions:
- a free-flying set-up where bees could fly at any distance from the size illusion before making decisions, and
- a constrained viewing set-up where bees could only view and make decisions about the illusion from one set distance.
How does a bee view size illusions?
To determine if bees could perceive size illusions, we first had to find a way to ask them.
We trained one group of bees to always choose the larger black square on a square white background and another group of bees to always choose the smaller black square on a square white background.
When bees had learnt to either choose larger or smaller sized black square targets, we manipulated the size of the background, thus trying to induce the perception of a visual illusion (similar to the Delboeuf Illusion).
We ran this experiment using our free-flying, unrestricted viewing condition and also using a restricted viewing condition where independent bees were unable to choose their own distance to make decisions.
Eureka! Training conditions explain why different animals see illusions differently. Bees in the unrestricted viewing condition perceived illusions, while bees in the restricted viewing condition did not see size illusions.
Now, we are interested in whether some past study results were due to experimental set-up: maybe more or even all animals could perceive illusions like humans, depending on the context in which they are viewing these illusions.
What does this mean for the evolution of vision?
Visual illusions are useful because they allow us to process complex scenes, with multiple pieces of information, as a whole by using context as a cue. Since different animals see size illusions, understanding how this works could help us learn more about how vision itself evolved.
One explanation of why such different animal species, from humans to bees, see size illusions is because an ancient ancestor had this ability, and it has been conserved throughout evolution. However, a more likely scenario is that the evolution of visual illusion perception is due to convergent evolution. This occurs when different species evolved the ability to perceive illusions separately.
The ability of bees to perceive a size illusion in a free-flying environment also has implications for flower evolution. Flowers could have evolved to exploit the ability of bees seeing illusions to make nectar areas look more appealing. One genus of flower, Wurmbea, appears to have illusionary properties such as differently sized flowers with patterns reminiscent of size illusions such as the Ebbinghaus and Delboeuf Illusions.
A very important lesson from this study is that viewing context can make scenes appear very different to reality. This is very important to remember when working on vision in humans or any other animal.
A Victorian man died yesterday after being stung by several bees. While bee sting deaths are rare (bees claim around two Australian lives each year), bees cause more hospitalisations than any venomous creature.
Around 60% of Australians have been stung by a honey bee; and with a population of more than 20 million, that’s a lot of us who have just experienced pain and some swelling.
So what happens when we’re stung by a bee, and what determines whether we’ll have a severe reaction?
How do bees sting?
Honey bees work as collective group that live as a hive. The group protects the queen, who produces new bees, with worker bees flying out to collect nectar or pollen to bring back to the hive.
Bees have a venom sac and a barbed stinger at the end of their abdomen. This apparatus is a defensive mechanism that is used if they feel under attack; to defend the hive from destruction. The barb from a bee sting pierces the skin to inject the venom, with the bee releasing pheromones that can incite other nearby bees to join the defensive attack.
The venom is a complex mixture of proteins and organic molecules, that when injected into our body can cause pain, local swelling, itching and irritation that may last for hours. The specific activity of some bee venom components have also been used to treat cancer.
Further reading: Curious Kids: Do bees ever accidentally sting other bees?
A single bee sting is almost always limited to these local effects. Some people, however, develop an allergy to some of these venom proteins. Anaphylaxis, a severe allergic reaction that is potentially life-threatening, is the most serious reaction our body’s immune system can launch to defend against the venom.
It is our body’s allergy to the bee venom, rather than the venom itself, that usually causes life-threatening issues and hospitalisation.
How do I know if I am allergic?
If you have not been stung by a bee before you are unlikely to be allergic to the venom. However, if you have been stung by a bee, there is the potential to develop an allergy. We do not know why some people become allergic and others don’t, but how often you are stung seems to play a role.
If you have experienced very large local reactions from a bee sting, or symptoms separate from the sting site (such as swelling, rashes and itchy skin elsewhere, dizziness or difficulty breathing) you may have an allergic sensitivity. Your doctor can assess you by taking a full history of reactions. Skin testing or blood allergy testing can help confirm or exclude potential allergy triggers.
An allergy specialist is key to assess people’s risk of severe allergic reactions (anaphylaxis).
There is an effective treatment for severe honey bee allergies, called immunotherapy. This involves the regular administration of venom extracts with doses gradually increased over a period of three to five years. This aims to desensitise the body’s immune system, essentially to “switch off” the allergic reaction to the venom.
Venom immunotherapy is very effective at preventing severe reactions and is available on the Pharmaceutical Benefit Scheme, whereas other immunotherapy treatments in Australia cost an average of A$1,200 per year.
First aid for a bee sting
Bees usually leave their barbed sting in the skin and then die. Remove the sting as soon as possible (within 30 seconds) to limit the amount of venom injected. Use a hard surface such as the edge of a credit card, car key or fingernail to flick/scratch out the barb.
For a minor reaction such as pain and local swelling, a cold pack may help relieve these symptoms.
If a bee stings you around your neck, or you find it difficult to breathe, or experience any wheezing, dizziness or light-headedness, seek medical advice urgently.
Despite being a species introduced by European settlers, the honey bee (Apis mellifera) plays an essential role within Australian agriculture. We need to appreciate their essential functions, and try to prevent stings.
If you see a bee let it be (sorry); don’t swat it or step on them. Our bees don’t attack unless they feel they need to defend their hive.
Do not attempt to locate a hive, call an expert.
The weather is getting warmer, and gardens are coming alive with bees, flies, butterflies, dragonflies, praying mantises, beetles, millipedes, centipedes, and spiders.
For some of us it is exciting to see these strange and wonderful creatures return. For others, it’s a sign to contact the local pest control company or go to the supermarket to stock up on sprays.
But while some bugs do us very few favours – like mozzies, snails and cockroaches – killing all insects and bugs isn’t always necessary or effective. It can also damage ecosystems and our own health.
Read more: The hidden secrets of insect poop
There are times when insecticides are needed (especially when pest populations are surging or the risk of disease is high) but you don’t have to reach for the spray every time. Here are five good reasons to avoid pesticides wherever possible, and live and let live.
1. Encourage the bees and butterflies, enjoy more fruits and flowers
Flowers and fruits are the focal points of even the smallest gardens, and many of our favourites rely on visits from insect pollinators. We all know about the benefits of European honey bees (Apis mellifera), but how about our “home grown” pollinators – our native bees, hover flies, beetles, moths and butterflies. All these species contribute to the pollination of our native plants and fruits and veggies.
You can encourage these helpful pollinators by growing plants that flower at different times of the year (especially natives) and looking into sugar-water feeders or insect hotels.
2. Delight your decomposers, they’re like mini bulldozers
To break down leaf litter and other organic waste you need decomposers. Worms, beetles and slaters will munch through decaying vegetation, releasing nutrients into the soil that can be used by plants.
The problem is that urban soils are frequently disturbed and can contain high levels of heavy metals that affects decomposer communities. If there are fewer “bugs” in the soil, decomposition is slower – so we need to conserve our underground allies.
You can help them out with compost heaps and worm farms that can be dug into the ground. It’s also good to keep some areas of your lawn un-mowed, and to create areas of leaf litter. Keeping your garden well-watered will also help your underground ecosystems, but be mindful of water restrictions and encouraging mosquitoes.
3. An army of beneficial bugs can eat your pests
Mantises and dragonflies are just some of the hundreds of fascinating and beautiful bugs we are lucky to see around our homes. Many of these wonderful creatures are predators of mozzies, house flies and cockroaches, yet people are using broad-spectrum insecticides which kill these beneficial bugs alongside the pests.
It may sound counterproductive to stop using pesticides in order to control pests around the home, but that’s exactly what organic farmers do. By reducing pesticides you allow populations of natural enemies to thrive.
Many farmers grow specific plants to encourage beneficial insects, which has been shown to reduce the damage to their crops.
This form of pest control in growing in popularity because spraying can result in insecticide resistance. Fortunately, it’s easy to encourage these bugs: they go where their prey is. If you have a good range of insects in your yard, these helpful predators are probably also present.
4. Your garden will support more wildlife, both big and small
Spraying with broad-spectrum pesticides will kill off more than just insects and spiders – you’re also going after the animals that eat them. The more insects are around, the more birds, mammals, reptiles and frogs will thrive in your backyard.
Baiting for snails, for example, will deter the blue-tongue lizards that eat them, so cage your vegetables to protect them instead. Keeping your garden well-watered, and including waterbaths, will also encourage a balanced ecosystem (but change the waterbaths regularly).
5. You and your family be happier and healthier
Engaging with nature increases well-being and stimulates learning in children. Insects are a fantastic way to engage with nature, and where better to do this than in your own back yard! Observing and experimenting on insects is a wonderful teaching tool for everything from life cycles to the scientific method. It will also teach your kids to value nature and live sustainably.
It’s also a hard truth that domestic pesticides present a significant risk of poisoning, especially for small children.
In reality, the risk of exposing your children to the pesticides far outweighs the nuisance of having a few bugs around. Instead, integrated pest management, which combines non-chemical techniques like cleaning of food residues, removal of potential nutrients, and sealing cracks and crevices, is safer for your family and your garden ecosystems.
Think globally, act locally
Your backyard has a surprising impact on the broader health of your neighbourhood, and gardens can make significant contributions to local biodiversity. Insects are an important part of ecosystem conservation, and encouraging them will improve the health of your local environment (and probably your health and well-being too).
In the end, insects and spiders are not out to get you. For the sake of our kids and our environment, you should give them a chance.
Lizzy Lowe, Postdoctoral researcher, Macquarie University; Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney, and Kate Umbers, Lecturer in Zoology, Western Sydney University
Chemical pesticides have been used for many years to control insect populations and remain the most important method of managing diseases carried by pests, including mosquitoes. However, insects have fought back by evolving resistance to many pesticides. There are now thousands of instances of evolved resistance, which make some chemical classes completely ineffective.
The Aedes mosquito, largely responsible for the spread of viruses like dengue and zika, has globally developed resistance to commonly used chemicals, including pyrethroids. Pyrethroids are the most used insecticides in the world, which includes the control of dengue outbreaks and quarantine breaches at air and sea ports.
In Asia and the Americas, pyrethroid resistance in Aedes mosquitoes is now widespread. In Australia, our mosquitoes have not developed these defences and pyrethroids are still very effective.
The difference lies in our stringent and careful protocols for chemical use. As the global community fights zika and other mosquito-borne diseases, there are lessons to be learned from Australia’s success.
Mosquitoes usually become resistant to pyrethroids through the mutation of a sodium channel gene that controls the movement of ions across cell membranes. Mutations in a single gene are enough to make mosquitoes almost completely resistant to the level of pyrethroids used in insecticides.
The mutations first arises in a population by chance, and are rare. However, they rapidly spread as resistant females breed. The more times a mosquito population is exposed to the same chemical, the more the natural selection process favours their impervious offspring.
Eventually, when many individuals in a population carry the resistance mutation, the chemical becomes ineffective. This can happen where insecticide “fogging” is common practice. Overseas, fogging is sometimes undertaken across entire neighbourhoods, several times a month, despite concerns about its effectiveness as well as its environmental and health impacts.
Once resistance develops, it can spread to non-resistant mosquito populations in other areas. Pest species, including mosquitoes, are often highly mobile because they fly or are carried passively (in vehicles, ships and planes) at any stage of their life cycle. Their mobility means mutations spread quickly, crossing borders and possibly seas.
We can still control Australian mosquitoes
Despite this, Australian populations of Aedes mosquitoes remain susceptible to pyrethroids. Aedes aegypti (the yellow fever mosquito) is the main disease-carrying mosquito in Australia. Its population is restricted to urban areas of northern Queensland, where dengue can occur.
Recent research found that all Australian populations of this species are still vulnerable to pyrethroids. None of the hundreds of mosquitoes tested had any mutations in the sodium channel gene, despite the high incidence of such mutations in mosquito populations of South-East Asia.
We believe these mosquitoes remain vulnerable to pyrethroids because in Australia pressure to select for resistance has been low.
Australia does not carry out routine fogging. If dengue is detected in an area, pyrethoids are used in highly regimented and limited fashion. Spraying is restricted to the insides of premises within selected house blocks, and then only for a short period.
Importantly, water-filled artificial containers, which can serve as a habitat for larvae, are treated with insect growth regulators, which do not select for the pyrethroid resistance mutations.
With chemical resistance growing around the world, it is more urgent than ever that we co-ordinate action to control and reduce risk of resistance. Unfortunately, no global guidelines exist to minimise the evolution of resistance in mosquitoes.
Adopting pesticide resistance management strategies has proven to be effective against other pests – for example, the corn earworm (Helicoverpa armigera). Guidelines include rotating different class of pesticides to deny pests the chance to develop resistance, and investing in non-chemical options such as natural predators of target pests.
Resistance management strategies are particularly critical for new pesticides that have different modes of attack, such as preventing juvenile insects from moulting, or attacking various chemical receptors.
To prolong the effectiveness of pesticides, we must develop these strategies before resistance begins to develop. North Queensland may be an example to the rest of the world on the best path forward.
Ary Hoffmann, Professor, School of BioSciences and Bio21 Institute, University of Melbourne; Nancy Margaret Endersby-Harshman, Research fellow, University of Melbourne, and Scott Ritchie, Professorial Research Fellow, James Cook University
Ten years ago, beekeepers in the United States raised the alarm that thousands of their hives were mysteriously empty of bees. What followed was global concern over a new phenomenon: Colony Collapse Disorder.
Since then we have realised that it was not just the US that was losing its honey bees; similar problems have manifested all over the world. To make things worse, we are also losing many of our populations of wild bees too.
Losing bees can have tragic consequences, for us as well as them. Bees are pollinators for about one-third of the plants we eat, a service that has been valued at €153 billion (US$168 billion) per year worldwide.
Ten years after the initial alarm, what is the current status of the world’s bee populations, and how far have we come towards understanding what has happened?
The current status of bees worldwide
Since the alarm was first raised, many countries have created new monitoring methods to judge the status of their bee stocks. As a result we have much more data on bee populations, although coverage is still patchy and differences in survey methods make it hard to compare between continents.
It is clear that bees in the United States are still struggling. Beekeepers can tolerate up to 15% losses of colonies over winter, but the US is massively above this threshold, having lost 28.1% of colonies over the 2015-16 winter.
Canada, by contrast, reported 16.8% losses. This is better, but still above the level of losses at which beekeepers can easily restock.
Only recently have we had data from central Europe. There, honey bees seem to be doing better: 11.9% losses in 2015-16. Meanwhile, in New Zealand surveys only began in the last year and have reported winter loss of 10.7%. Australia does not yet have a countrywide survey of the state of bee colonies.
Honey bees are not the only bees that we should care about: wild bees are vital pollinators too. Some plants are pollinated by only one wild bee species, such as the macropis bees that forage on the loosetrife plant.
Unsurprisingly, we have much less data on wild bees than honey bees, and those data we do have point to bigger concerns. For our wild bees we only really have good data for populations that are endangered or that have completely disappeared. Between 2008 and 2013, wild bee diversity in the US dropped by 23%, and a previously common bumblebee species was recently listed as endangered.
Do we understand why?
The good news is that the past decade has seen plenty of progress in understanding the mystery of Colony Collapse Disorder. The bad news is that we now recognise it as a complex problem with many causes, although that doesn’t mean it is unsolvable.
For all bees, foraging on flowers is a hard life. It is energetically and cognitively demanding; bees have to travel large distances to collect pollen and nectar from sometimes hard-to-find flowers, and return it all to the nest. To do this they need finely tuned senses, spatial awareness, learning and memory.
Anything that damages such skills can make bees struggle to find food, or even get lost while trying to forage. A bee that cannot find food and make it home again is as good as dead.
Because of this, bee populations are very vulnerable to what we call “sublethal stressors” – factors that don’t kill the bees directly but can hamper their behaviour.
In a recently published review, we argue that modern agriculture and industry have created a host of sublethal stressors that damage bees’ cognition. For example, diesel fumes and neonicotinoid pesticides both reduce bees’ foraging efficiency by disturbing chemical communications in their brains. Modern intensive agriculture disturbs bee nutrition, which impairs their brain. Climate change interferes with the relationship between bees and the plants on which they feed.
In addition, managed honey bees are afflicted by a range of pests, viruses and predators that have been spread around the world as a side-effect of international trade. The worst is the ominously named Varroa destructor mite, which causes brain development disorders.
What can we do?
At the global level, to preserve our bees we have to improve the environments in which they collect food. Every small action can make a difference. Planting flower borders with bee-friendly flowers in your garden can provide food for both wild and domestic bees. You can reduce or eliminate the use of herbicides or pesticides when gardening. Even mowing the lawn less often can help bees out.
In Australia, we are fortunate in that our bees seem to be doing better than many other parts of the world. The Varroa mite has not yet invaded our shores, and in many areas bees can access pesticide-free bushland (although unlike Europe, Australia has not yet banned use of neonicotinoids in agriculture).
Australia also has an incredibly rich diversity of wild native bees: up to 1,600 different species, including our emblematic stingless bees. Even so, to protect this diversity we need better surveys of how these species are doing.
Ten years on from the alarm over disappearing bees, it is fair to say we now know the nature of the problem and what can be done to fix it. It’s up to us to take the steps needed to sustain these precious pollinators of our food for the future.
The link below is to an article that looks at 5 ways to deal with ticks – which also mentions those great pests of the Aussie bush, the drop bears.