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.
Many people on a tropical island getaway might take a jungle hike, or learn about the local wildlife. My colleagues and I went one better: we tracked down the world’s biggest bee species, which hadn’t been spotted for decades, while on holiday in Indonesia’s North Molucca islands.
Wallace’s giant bee, Megachile pluto, is fascinating for many reasons. It’s the largest of all known living bees, with a body length about that of a human thumb and a wingspan of more than 6cm. What’s more, its last confirmed sighting in the field was in 1981. After numerous efforts to rediscover it, it was unclear whether the species still remained in the wild.
The bee also has a special place in scientific history. It was first collected by the British naturalist and explorer Alfred Russel Wallace in 1859, as part of his work in the Malay Archipelago. He described the female bee as “a large black wasp-like insect, with immense jaws like a stag-beetle”.
Wallace not only independently derived the theory of natural selection as an explanation for evolution alongside Charles Darwin, but his detailed studies of the distribution of animals gave rise to the famous Wallace Line, a boundary that splits Australia and Asia and helps to explain the distribution patterns of many plants and animals.
Wallacea: a living laboratory of evolution
How did four biologists from across the globe, two from Australia (myself and Glen Chilton) and two from the United States (Eli Wyman and Clay Bolt), end up on this journey?
My involvement started at the prompting of Glen, who although specialising in ornithology and writing was interested in both Wallace and the rediscovery of potentially extinct species. He became aware of the existence of the world’s largest bee, and after two years of cajoling I agreed that searching for the bee would represent an excellent holiday.
During the planning for our trip, we became aware that Eli and Clay were also, independently, planning to travel to the Moluccas to search for M. pluto. After a brief Skype call we decided it made sense to join forces and collaborate. So despite our two duos never having met in person, we were a team heading out into the field.
And what a great team it was: Eli’s expertise in all things bee-related; Clay’s fantastic photographic skills; Glen’s enthusiasm and knowledge of Wallace; and my own fascination with the evolution of insect behaviour.
On the ground
We converged on the island of Ternate and began our search across the North Molucca islands for termite mounds containing bee-sized holes, helped by two excellent local guides, Ekawati Ka’aba and Iswan Maujad.
M. pluto is a solitary bee species that forms communal nests inside termite mounds, using its mandibles to collect and apply tree resin to the inner walls of its nest. So we knew what to look out for.
After five fruitless days of searching termite mounds, we were about to call it quits and head for a late lunch when we spotted another mound near the edge of a path.
Inspection with a torch and binoculars revealed a hole that looked promising. Clay scaled the tree and reported that the hole looked to be lined with resin – very exciting. Our guides constructed a platform from branches, we inspected the hole in more detail, and there she was. Cue intense excitement and cries of jubilation as we all rushed to peer inside and catch a glimpse.
Now that we had the bee, we had to be able to prove it, so we put away our iPhone cameras in favour of better-quality (but riskier: the bee might escape!) footage with more professional photographic and video equipment. We gently coaxed her out of her nest and into a small flight chamber, and then eventually Clay got the magic shot, where we released the bee back onto her nest and photographed her at the entrance to her home. Mission accomplished.
Confirming that the world’s largest bee species is still alive is an enticing development for ecologists. We can learn a lot about the ecology, behaviour and ecological significance of this giant. Amid a global decline in many insects, it’s wonderful to discover this special species is still surviving.
We also hope our discovery will galvanise conservation movements in Indonesia, and we were inspired by the reception our journey met with many people in the conservation and forestry fields of the North Molucca islands.
We would love more work to be done to assess the bee’s current conservation status. Plans to produce a documentary about Wallace and the rediscovery of this bee are underway, and we hope that its rediscovery provides further impetus to conservation efforts generally.
Not a bad outcome for a holiday!
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.
Pollinating insects like bees, butterflies and flies have had a rough time of late. A broad library of evidence suggests there has been a widespread decline in their abundance and diversity since the 1950s. This matters because such insects are critical both for the reproduction of wild plants and for agricultural food production.
The decline of these pollinators is linked with destruction of natural habitats like forests and meadows, the spread of pests such as Varroa mite and diseases like foulbrood, and the increasing use of agrochemicals by farmers. Although there have been well documented declines in managed honeybees, non-Apis (non-honeybee) pollinators such as bumblebees and solitary bees have also become endangered.
There are more than 800 wild (non-honey) bee species in Europe alone. Seven are classified by the IUCN Redlist as critically endangered, 46 are endangered, 24 are vulnerable and 101 are near threatened. Collectively, losing such species would have a significant impact on global pollination.
Though much of the media focus is on honeybees, they are responsible for only a third of the crop pollination in Britain and a very small proportion of wild plant pollination. A range of other insects including butterflies, bumblebees and small flies make up for this pollination deficit.
Not all pollinators are created equal
Pollinators also vary in their effectiveness due to their behaviour around flowers and their capacity to hold pollen. Bigger and hairier insects can carry more pollen, while those that groom themselves less tend to be able to transfer pollen more effectively. Bumblebees, for example, make excellent pollinators (far superior to honeybees) as they are big, hairy and do not groom themselves as often.
Where they are in decline, honeybees suffer primarily from pests and diseases, a consequence of poor nutrition and artificially high population density. This differs from other pollinators, where the decline is mainly down to habitat destruction. It seems pesticides affect all pollinators.
Save (all) the bees
Curiously, the issues facing non-Apis pollinators may be exacerbated by commercial beekeeping, and attempts to help honeybees may even harm efforts to conserve wild pollinators.
The problem is that there are only so many flowers and places to nest. And once the numbers of honeybees have been artificially inflated (commercial-scale beekeeping wouldn’t exist without humans) the increased competition for these resources can push native non-Apis pollinators out of their natural habitats. Honeybees also spread exotic plants and transmit pathogens, both of which have been shown to harm other pollinators.
Over the coming decades, farmers and those who regulate them are faced with a tough challenge. Agricultural output must be increased to feed a growing human population, but simultaneously the environmental impact must be reduced.
The agriculture sector has tried to address the need to feed a growing population through conventional farming practices such as mechanisation, larger fields or the use of pesticides and fertiliser. Yet these have contributed to widespread destruction of natural landscapes and loss of natural capital.
Limited resources and land use pressure require conservation strategies to become more efficient, producing greater outcomes from increasingly limited input.
So-called agri-environment schemes represent the best way to help insect pollinators. That means diversifying crops, avoiding an ecologically-fragile monoculture and ensuring that the insects can jump between different food sources. It also means protecting natural habitats and establishing ecological focus areas such as wildflower strips, while limiting the use of pesticides and fertilisers.
As pollinating insects need a surprisingly large area of land to forage, linking up restored habitats on a larger scale provides far more evident and immediate benefits. However, so far, connections between protected areas have not been a priority, leading to inefficient conservation.
We need a substantial shift in how we think about pollinators. Encouraging land managers to work cooperatively will help create bigger, more impactful areas to support pollinators. In future, conservation efforts will need to address declines in all pollinators by developing landscapes to support pollinator communities and not just honeybees.