The recent story of four live bees pulled from inside a woman’s eye quickly grabbed people’s attention. News reports claimed the bees were “sweat bees”, the common name for species in the bee family Halictidae.
There are some contradictory and unlikely statements in the many news reports covering this story, so it’s hard to know what actually happened. The images accompanying many reports, which some reporters captioned as the live sweat bees in the Taiwanese woman’s eye, are actually uncredited images from a completely unrelated story – this report by Hans Bänzinger of a stingless bee species (Lisotrigona cacciae) collecting tears from his eye in Thailand.
All in all, we would consider it extremely unlikely for multiple adult insects to survive inside a human eye for very long. Most halictid bees are too large to get trapped in your eye unnoticed. Female sweat bees also have stingers so you would definitely know straight away!
But whether this story is accurate or not, there are bees who would happily feast on human tears – and blood, sweat and even dead animals. Flower-loving insects like bees and butterflies often seek out other food sources that are at odds with their pretty public image.
So why would bees hang around someone’s eye in the first place? It’s a bit of a myth that all bees only collect pollen and nectar for food. There are bee species all over the world that also feed on the bodily fluids of living and dead animals, including animal honeydew, blood, dead meat, dung, sweat, faeces, urine and tears. This is a source of important nutrients they can’t get from flowers, like sodium, or protein and sugar when floral resources are scarce.
The term “sweat bee” is used colloquially for bees that ingest human sweat as a nutritional resource.
Many people think the term only refers to bees in the Halictidae family. But not all halictid bee species are known to collect sweat, while many species in the Apidae family, particularly stingless bees, are common sweat-collectors in tropical areas around the world. Swarms of sweat-seeking stingless bees can be a nuisance to sweaty humans in tropical places.
And it’s not just sweat; stingless bees have quite diverse tastes and collect many non-floral resources. There are also a few neotropical Trigona species that collect animal tissue as their main protein source, instead of pollen. These species collect floral nectar and make honey, like other stingless bees, but predominantly scavenge on carrion (they are technically know as obligate necrophages).
Regardless of taxonomy, bees that are attracted to sweat often use other bodily fluids too, like tears. Tear-feeding is such a common behaviour among insects, it has an official name: lachryphagy. Some stingless bees from south Asia, such as the Lisotrigona species mentioned above, are well-known lachryphagous insects, often seen congregating in groups around animal eyes (including humans) to harvest fluids. They don’t harm the animal in the process, although their activity might be a nuisance to some.
In South America, Centris bees are large, solitary apid bees, in the same family as stingless bees and honey bees. These bees are often observed drinking tears from animal eyes; published observations include interactions with caimans and turtles.
Bees aren’t the only insects that regularly drink from animal eyes. Our world-famous hand gesture, the Aussie salute, is designed to deter the common bush flies (Musca species) that hang around our faces on hot days, looking for a quick drink of sweat, saliva or tears. These flies are also commonly seen clustered around livestock eyes on farms.
The feeding habits of butterflies would shock many people who think they are dainty, angelic flower-frequenting creatures. Butterflies are common feeders on dung, carrion, mud and various other secretions, including animal tears. Moths are also well-known nocturnal feeders on animal tears, even while they are sleeping.
Although most of us wouldn’t like the idea of an insect drinking out of our eyelid, this isn’t the stuff of nightmares. It’s just another fascinating, but little-known, story of how animals interact with each other. From a bee’s perspective, an animal’s eye is just another food source.
It produces secretions that provide important nutrients, just like a flower produces nectar and pollen. Although entomologists know this behaviour occurs, we still don’t fully understand how common it is, or how reliant pollinating insects are on different animals in their local environment.
But, while tear-collecting behaviour is normal for many insects, the odds of live bees crawling inside your eye to live are extremely low.
The humble honeybee can use symbols to perform basic maths including addition and subtraction, shows new research published today in the journal Science Advances.
Despite having a brain containing less than one million neurons, the honeybee has recently shown it can manage complex problems – like understanding the concept of zero.
Honeybees are a high value model for exploring questions about neuroscience. In our latest study we decided to test if they could learn to perform simple arithmetical operations such as addition and subtraction.
Addition and subtraction operations
As children, we learn that a plus symbol (+) means we have to add two or more quantities, while a minus symbol (-) means we have to subtract quantities from each other.
To solve these problems, we need both long-term and short-term memory. We use working (short-term) memory to manage the numerical values while performing the operation, and we store the rules for adding or subtracting in long-term memory.
Although the ability to perform arithmetic like adding and subtracting is not simple, it is vital in human societies. The Egyptians and Babylonians show evidence of using arithmetic around 2000BCE, which would have been useful – for example – to count live stock and calculate new numbers when cattle were sold off.
But does the development of arithmetical thinking require a large primate brain, or do other animals face similar problems that enable them to process arithmetic operations? We explored this using the honeybee.
How to train a bee
Honeybees are central place foragers – which means that a forager bee will return to a place if the location provides a good source of food.
We provide bees with a high concentration of sugar water during experiments, so individual bees (all female) continue to return to the experiment to collect nutrition for the hive.
In our setup, when a bee chooses a correct number (see below) she receives a reward of sugar water. If she makes an incorrect choice, she will receive a bitter tasting quinine solution.
We use this method to teach individual bees to learn the task of addition or subtraction over four to seven hours. Each time the bee became full she returned to the hive, then came back to the experiment to continue learning.
Addition and subtraction in bees
Honeybees were individually trained to visit a Y-maze shaped apparatus.
The bee would fly into the entrance of the Y-maze and view an array of elements consisting of between one to five shapes. The shapes (for example: square shapes, but many shape options were employed in actual experiments) would be one of two colours. Blue meant the bee had to perform an addition operation (+ 1). If the shapes were yellow, the bee would have to perform a subtraction operation (- 1).
For the task of either plus or minus one, one side would contain an incorrect answer and the other side would contain the correct answer. The side of stimuli was changed randomly throughout the experiment, so that the bee would not learn to only visit one side of the Y-maze.
After viewing the initial number, each bee would fly through a hole into a decision chamber where it could either choose to fly to the left or right side of the Y-maze depending on operation to which she had been trained for.
At the beginning of the experiment, bees made random choices until they could work out how to solve the problem. Eventually, over 100 learning trials, bees learnt that blue meant +1 while yellow meant -1. Bees could then apply the rules to new numbers.
During testing with a novel number, bees were correct in addition and subtraction of one element 64-72% of the time. The bee’s performance on tests was significantly different than what we would expect if bees were choosing randomly, called chance level performance (50% correct/incorrect)
Thus, our “bee school” within the Y-maze allowed the bees to learn how to use arithmetic operators to add or subtract.
Why is this a complex question for bees?
Numerical operations such as addition and subtraction are complex questions because they require two levels of processing. The first level requires a bee to comprehend the value of numerical attributes. The second level requires the bee to mentally manipulate numerical attributes in working memory.
In addition to these two processes, bees also had to perform the arithmetic operations in working memory – the number “one” to be added or subtracted was not visually present. Rather, the idea of plus one or minus “one” was an abstract concept which bees had to resolve over the course of the training.
Showing that a bee can combine simple arithmetic and symbolic learning has identified numerous areas of research to expand into, such as whether other animals can add and subtract.
Implications for AI and neurobiology
There is a lot of interest in AI, and how well computers can enable self learning of novel problems.
Our new findings show that learning symbolic arithmetic operators to enable addition and subtraction is possible with a miniature brain. This suggests there may be new ways to incorporate interactions of both long-term rules and working memory into designs to improve rapid AI learning of new problems.
Also, our findings show that the understanding of maths symbols as a language with operators is something that many brains can probably achieve, and helps explain how many human cultures independently developed numeracy skills.
This article has been published simultaneously in Spanish on The Conversation Espana.
Walking through our gardens in Australia, we may not realise that buzzing around us is one of our greatest natural resources. Bees are responsible for pollinating about a third of food for human consumption, and data on crop production suggests that bees contribute more than US$235 billion to the global economy each year.
By pollinating native and non-native plants, including many ornamental species, honeybees and Australian native bees also play an essential role in creating healthy communities – from urban parks to backyard gardens.
Despite their importance to human and environmental health, it is amazing how little we know how about our hard working insect friends actually see the world.
By learning how bees see and make decisions, it’s possible to improve our understanding of how best to work with bees to manage our essential resources.
How bee vision differs from human vision
A new documentary on ABC TV, The Great Australian Bee Challenge, is teaching everyday Australians all about bees. In it, we conducted an experiment to demonstrate how bees use their amazing eyes to find complex shapes in flowers, or even human faces.
Humans use the lens in our eye to focus light onto our retina, resulting in a sharp image. By contrast, insects like bees use a compound eye that is made up of many light-guiding tubes called ommatidia.
The top of each ommatidia is called a facet. In each of a bees’ two compound eyes, there are about 5000 different ommatidia, each funnelling part of the scene towards specialised sensors to enable visual perception by the bee brain.
Since each ommatidia carries limited information about a scene due to the physics of light, the resulting composite image is relatively “grainy” compared to human vision. The problem of reduced visual sharpness poses a challenge for bees trying to find flowers at a distance.
To help draw bees’ attention, flowers that are pollinated by bees have typically evolved to send very strong colour signals. We may find them beautiful, but flowers haven’t evolved for our eyes. In fact, the strongest signals appeal to a bee’s ability to perceive mixtures of ultraviolet, blue and green light.
Building a bee eye camera
Despite all of our research, it can still be hard to imagine how a bee sees.
So to help people (including ourselves) visualise what the world looks like to a bee, we built a special, bio-inspired “bee-eye” camera that mimics the optical principles of the bee compound eye by using about 5000 drinking straws. Each straw views just one part of a scene, but the array of straws allows all parts of the scene to be projected onto a piece of tracing paper.
The resulting image can then be captured using a digital camera. This project can be constructed by school age children, and easily be assembled multiple times to enable insights into how bees see our world.
Because bees can be trained to learn visual targets, we know that our device does a good job of mimicking a bees visual acuity.
Student projects can explore the interesting nexus between science, photography and art to show how bees see different things, like carrots – which are an important part of our diet and which require bees for the efficient production of seeds.
Understanding bee vision helps us protect bees
Bees need flowers to live, and we need bees to pollinate our crops. Understanding bee vision can help us better support our buzzy friends and the critical pollination services they provide.
In nature, it appears that flowers often bloom in communities, using combined cues like colour and scent to help important pollinators find the area with the best resources.
Having lots of flowers blooming together attracts pollinators in much the same way that boxing day sales attract consumers to a shopping centre. Shops are better together, even though they are in competition – the same may be true for flowers!
This suggests that there is unlikely to be one flower that is “best” for bees. The solution for better supporting bees is to incorporate as many flowers as possible – both native and non native – in the environment. Basically: if you plant it, they will come.
We are only starting to understand how bees see and perceive our shared world – including art styles – and the more we know, the better we can protect and encourage our essential insect partners.
Watching plants and pollinators such as bees can teach us a lot about how complex networks work in nature.
There are thousands of species of bees around the world, and they all share a common visual system: their eyes are sensitive to ultraviolet, blue and green wavelengths of the light spectrum.
This ancient colour visual system predates the evolution of flowers, and so flowers from around the world have typically evolved colourful blooms that are easily seen by bees.
For example, flowers as perceived by ultraviolet-sensitive visual systems look completely different than what humans can see.
However, we know that flowers also produce a variety of complex, captivating scents. So in complex natural environments, what signal should best enable a bee to find flowers: colour or scent?
Our latest research uncovered a surprising outcome. It seems that rather that trying to out-compete each other in colour and scent for bee attention, flowers may work together to attract pollinators en masse. It’s the sort of approach that also works in the world of advertising.
Daunting amount of field work
Classic thinking would suggest that flowers of a particular species should have reasonably unique flower signatures. It makes sense that this should promote the capacity of a bee to constantly find the same rewarding species of flower, promoting efficient transfer of pollen.
So a competition view of flower evolution for different flower species with the same colour – for example purple – would suggest that each flowering plant species should benefit from having different scents to enable pollinator constancy and flower fidelity. By the same logic, flowers with the same scents should have different colours so they’re easily distinguished.
To know for sure what happens requires a daunting amount of field work. The challenges include measuring flower colours using a spectrophotometer (a very sensitive instrument that detects subtle colour differences) and also capturing live flower scent emissions with special pumps and chemical traps.
At the same time, in order to record the actual pollinator “clientele” of the flowers, detailed recordings of visits are required. These data are then built into models for bee perception. Statistical analyses allow us to understand the complex interactions that are present in a real world evolved system.
Not what we thought
And what we found was unexpected. In two new papers, published in Nature Ecology & Evolution and in Nature Communications, we found the opposite to competition happens: flowers have evolved signals that work together to facilitate visits by bees.
So flowers of different, completely unrelated species might “smell like purple”, whilst red coloured species share another scent. This is not what is expected at all by competition, so why in a highly evolved classical signal receiver has this happened?
The data suggests that flowers do better by attracting more pollinators to a set of reliable signals, rather than trying to use unique signals to maximise individual species.
By having reliable multimodal signals that act in concert to allow for easy finding of rewarding flowers, even of different species, more pollinators must be facilitated to transfer pollen between flowers of the same species.
Lessons for advertising
A lot of research on advertising and marketing is concerned with consumer behaviour: how we make choices. What drives our decision-making when foraging in a complex environment?
While a lot of modern marketing emphasises product differentiation and competition to promote sales, our new research suggests that nature can favour facilitation. It appears that by sharing desirable characteristics, a system can be more efficient.
This facilitation mechanism is sometimes favoured by industry bodies, for example Australian avocados and Australian honey. En masse promotion of the desirable characteristics of similar products can grow supporter base and build sales. Our research suggests evolution has favoured this solution, which may hold important lessons for other complex market based systems.
A successful colour–scent combination targeted at attracting bees can be adopted by several different plant species in the same community, implying that natural ecosystems can function as a “buyers markets”.
We also know from research that flowers can evolve and change colours to suit the local pollinators. Colours can thus be changed by flowers if instead of bees pollinating flowers, flies, with different colour perception and preferences, dominate the community.
These findings can also prove useful for identifying those colour-scent combinations that are the most influential for the community. This way, the restoration of damaged or disrupted plant-pollinator communities can become better managed to be more efficient in the future.
When next enjoying a walk in a blooming meadow, remember plants’ strategies. The colourful flowers and the mesmerising scents you experience may have evolved to cleverly allure the efficient pollinators of the region.
The retail chain Bunnings will stop selling the Confidor pesticide brand for homes and gardens by the end of 2018.
Neonicotinoids along with fipronil, another systemic insecticide that has also been blamed for bee deaths, are widely used in Australia on major crops such as maize, canola and cotton.
Between them they account for up to 30% of global insecticide sales. Will banning these insecticides stop the decline of bees worldwide?
Mites and disease
Insects are in trouble. A recent study found an 80% decline in flying insects, including butterflies, moths and wild bees, in German nature reserves. This has prompted questions about the impact of large-scale intensive agriculture.
Colony collapse disorder, in which worker bees dramatically disappear from honey bee hives, increased hugely in the decade up to 2013, particularly in the United States and Europe. This caused international concern and led to a ban on neonicotinoids and fipronil by the European Union in 2013.
However, there are no reports of colony collapse disorder in Australia, according to the Australian Pesticides and Veterinary Medicines Authority, which regulates the use of pesticides and monitors the effect of insecticides on bees. Why not?
We don’t fully understand the causes of colony collapse in honey bees, but it appears that a likely culprit is the Varroa mite and the lethal viruses it transmits. This parasite feeds on both larvae and adult bees, and has been blamed for infecting vast numbers of bees with several viruses including deformed wing virus.
Australia’s honey bees, in contrast to the rest of the world, are still free of Varroa mites. A CSIRO survey of 1,240 hives across Australia found that deformed wing virus is also not present. The absence of both the mite and the viruses it carries may help to explain why colony collapse has not (yet) been observed in Australia.
Pesticide and fungicides, oh my!
While there is clear evidence of harm to bees from the use of neonicotinoids and fipronil, particularly from drift during application, their role as the direct cause of colony collapse is not proven.
And while they can be harmful, neonicotinoids are not necessarily the biggest chemical threat to bees. Perhaps surprisingly, fungicides appear to be at least as significant.
One study found that bees that eat pollen with high levels of fungicide are more likely to be infected with a pathogen called Nosema. Other research showed that presence of the fungicide chlorothalonil was the best predictor of incidence of Nosema in four declining species of bumblebees. What’s more, the toxicity of neonicotinoids to honey bees doubles in the presence of common fungicides.
This is not to say that Australian bees are safe, or that neonicotinoids are not harmful. Australia has more than 5,000 native bee species, and studies suggest that the main impacts of neonicotinoids are on wild bees rather than honey bees in hives. The combination of widescale use of multiple agrochemicals, loss of plant and habitat diversity, and climate change is a significant threat to both wild and domesticated bees.
And if the Varroa mite and the viruses it carries were to arrive on our shores, the impact on Australia’s honey bees could be catastrophic.
Banning pesticides affects farmers
The EU insecticide ban left Europe’s farmers with few alternatives. Surveys of 800 farms across the EU suggest that farmers have adapted by increasing the use of other insecticides, particularly synthetic pyrethroids, as well altering planting schedules to avoid pests, and increasing planting rates to compensate for losses. Most farmers reported an overall increase in crop losses, in costs of crop protection and in time needed to manage pests.
A ban on fipronil and neonicotinoids would create similarly significant problems for Australian farmers, increasing costs and reducing the efficacy of crop protection. As in Europe, they would potentially increase use of synthetic pyrethroids, organophosphates and carbamates, many of which are even more harmful to bees and other insects.
Reliance on a more limited range of insecticides could also worsen the incidence of insecticide resistance and destabilise Australia’s efforts to balance resistance management and pest control with preserving beneficial insects.
Further development of these sophisticated pest management strategies, with emphasis on the use of less harmful alternatives such as microbial and biological controls, offers a route to a more effective, long-term solution to the decline in insects and bee health.
A ban on neonicotinoids might give campaigners a buzz, but it might not save the bees.