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Velvet ants: flamboyant and fuzzy with extreme PPE
Despite their name and looks, velvet ants are actually wasps.
Many of these delightfully fuzzy insects exhibit bright, contrasting shades of black with red, orange or white. Their bold bodies serve as a clear warning that you should keep a respectful distance - and for good reason.
Female velvet ants spend almost their entire lives alone, searching for places to lay their eggs. One big challenge of this nomadic lifestyle is the constant risk of being ambushed by would-be predators.
Fortunately for the wasps, they have evolved an extensive arsenal of defences that mean they can thwart most attacks.
What is a velvet ant?
There are about 8,000 species in the wasp family Mutillidae. This group is more commonly known as velvet ants, a name that comes from the females' resemblance to large, hairy ants.
Velvet ants are solitary insects. Males have wings and search for the wingless females on the ground. Once they find each other and mate, the wasps go their separate ways.
When the female is ready to lay her eggs, instead of digging or building a nest, she infiltrates those of other species. Velvet ants have a parasitoid lifestyle, laying their eggs on the defenceless pupae of other insects such as solitary ground-nesting wasps, although there is a diversity of hosts across the whole family. The velvet ant larva then hatches and proceeds to eat the host pupa, before it itself pupates and emerges from the nest as an adult velvet ant.
Their hosts can be spread some distances apart, and as female velvet ants usually lay only one egg per pupa, they can spend a lot of time out in the open on a quest for nests or other hosts. To avoid becoming another animal's dinner, velvet ants have evolved a formidable collection of defence mechanisms.
Velvet ants have a series of anti-predator warning signals, including bright colours, a defensive chemical odour and a loud squeak. These tell a predator that the wasp is not worth pursuing.
Bright colours are one way for velvet ants to tell predators that they aren't worth pursuing as a meal. This black and orange species is Dasymutilla aureola, which is found in the western United States. © Ken-ichi Ueda via Wikimedia Commons (CC BY 4.0)
Female wasps are restricted to life on the ground, without the easy option of flying away from danger. But where flight muscles would be are actually bulky leg muscles, making these insects quick and strong. In 1977, scientists found that when chased, the largest species of velvet ant, Dasymutilla occidentalis, could scurry at speeds of about 14 centimetres per second (or 0.5 kilometres per hour).
If a swift getaway isn't an option, their exoskeleton is incredibly tough. It takes about 11 times more force to squish a velvet ant than a honeybee. Velvet ants' bodies are also rounded, meaning that attempted bites and stings tend not to do any damage.
If the predator still doesn't let up, the painful wallop of a velvet ant's sting usually convinces them to let go.
No animal living today is known to specifically target velvet ants, but a 2018 paper found that female velvet ants are 'nearly impervious' to attacks by a variety of insectivores. In over 100 observed interactions between velvet ants and potential predators (including toads, lizards and shrews), only one wasp was successfully consumed.
How painful is a velvet ant's sting?
A velvet ant's defensive sting is delivered through a stinger that is up to half the length of its body.
The Pain Scale for Stinging Insects ranks the discomfort of insect stings on a scale of zero to four. How painful a velvet ant's sting is appears to vary depending on the species. For example, an unnamed nocturnal species scores 1.5, making it less painful than a western honeybee, whereas the glorious or thistledown velvet ant (Dasymutilla gloriosa) matches the bee with a score of two.
This stinger belongs to the red velvet ant (Dasymutilla occidentalis), a species that is found in the United States. Image: USGS Bee Inventory and Monitoring Lab via Flickr
But with an impressive ranking of three on the scale, Dasymutilla klugii currently takes the win for the most painful velvet ant sting. Justin Schmidt, an entomologist and the creator of the scale (and winner of an Ig Nobel Prize in 2015), vividly describes it as feeling like 'hot oil from the deep fryer spilling over your hand'.
A sting from D. klugii is only outmatched by the warrior wasp (Synoeca septentrionalis), tarantula hawk (Pepsis sp.) and bullet ant (Paraponera clavata), which all score at an unimaginable level four for pain.
Velvet ants are sometimes called cow killers due to the excruciating pain a sting can impart, although cows aren't likely to be in any real danger. Stinging is the wasp's last resort, used to shock a predator into letting go, allowing the wasp to get away rather than to seriously harm or kill.
Velvet ant venom is about 25 times less toxic than a honeybee's. Also, unlike social wasps such as Asian giant hornets and honeybees that chemically call in their nestmates to help protect their colony from intruders, velvet ants are solitary - so in most cases a predator will only be facing the sting of one wasp at a time.
Velvet ants aren't actively aggressive, but they also won't forgive you for picking them up. It's best to leave them alone and watch these animals from a distance.
Dasymutilla klugii has the most painful sting of all the known velvet ants. Image: Insects Unlocked via Flickr (CC0 1.0)
Why are velvet ants so colourful?
Velvet ants are often brightly coloured, commonly featuring red, orange, yellow, black and white.
Their striking colours are aposematic signals. Aposematism has evolved in a variety of animals and warns predators that an animal has defences such as being toxic or possessing a venomous sting, which make them not worth attacking. These signals benefit both the prey and predator: one avoids being eaten and the other avoids a rather unpleasant experience.
Aposematic signals often take the form of bold colours, for example in the vibrant but toxic poison dart frog family Dendrobatidae, although smells and sounds can also be aposematic.
Experiments have shown that the bold red and black colouring of the red velvet ant (Dasymutilla occidentalis) appears to cause some predators to be reluctant to attack a potential prey item © Judy Gallagher via Flickr (CC BY 2.0)
Bright colours make an animal more conspicuous to predators, usually contrasting well with common green and brown terrestrial backgrounds. Some animals, such as swallowtail butterfly caterpillars, however, can be aposematic close up but also have colouring that allows them to melt into the background when viewed from a distance.
To test the effect of velvet ants' colours on predators, scientists carried out experiments with birds where some mealworms were painted red and black to look like the wasp Dasymutilla occidentalis. These were left uneaten by the birds, whereas tan-coloured mealworms were all consumed immediately. When a live velvet ant was served, the birds appeared hesitant to visit the feeder at all.
Velvet ants also use sounds as a warning signal to predators. These insects have a stridulatory organ - where two parts of the abdomen are scraped together - which allows them to make a sharp squeaking sound when they feel threatened. In a trial with a shrew, the small mammal repeatedly attacked the velvet ant, but every time the insect stridulated, the shrew backed off.
Leucospilomutilla cerbera is found in South America and features bold black and white colouring
Müllerian mimicry rings
In North America, a huge number of velvet ant species can be divided into eight distinct groups based on their distribution and the similarity of their aposematic colouration. These rings of species represent one of the largest known complexes of Müllerian mimicry in the world.
Müllerian mimicry, a concept first proposed in the 1870s, is a phenomenon where well-defended species have evolved to mimic each other's warning signals to their mutual benefit. For velvet ants, sharing defences like colour, sting and stridulation may encourage predators to rapidly learn to avoid multiple species of the wasps from very few predation events.
In northern Mexico, Texas and southern New Mexico, insectivorous predators will commonly find themselves faced with black velvet ants with abdomens coated in a flaming orange fuzz. This distribution and colouring make up the Texan mimicry ring, comprising 14 species of velvet ant in two genera.
Seventeen species found in North America's warm deserts, including the Sonoran, Mojave and Chihuahuan, are typically white with some black colouration, making up what is known as the Desert ring. Members of the Tropical ring, 57 species from 10 genera found from southern Mexico to Panama, feature bold patterns of black and yellow.
Dasymutilla pulchra is a velvet ant species seen in central and South America. It is a member of the Tropical Müllerian mimicry ring, featuring bold black and yellow markings. © Julián-Caballero C. Camilo via Wikimedia Commons (CC BY 4.0)
The study included all 21 genera of velvet ant present in North America and found that only 15 of the 351 species analysed didn't fit into one of the eight mimicry rings.
A few species seem to have gone down a different evolutionary route and are camouflaged. One of the most striking examples is the desert-dwelling thistledown velvet ant, which may be mimicking the fluffy white seed cases of the creosote bush, which is found in the same habitats.
It can be tricky to determine whether a male and female velvet ant are the same species, as they don't necessarily closely resemble each other or even participate in the same mimicry ring.
Velvet ants in the UK
Three species of Mutillidae velvet ant can be found in the UK, but only two are classic velvet ants and sightings are relatively rare.
Smicromyrme rufipes is mainly found in southeast England as far north as Oxfordshire. It's usually associated with warmer, sandy areas such as coastal dunes and heathland. This species is also found across mainland Europe.
Mutilla europaea is larger and slightly more widespread, although again is mostly found in the south of England. However, in 2017 this species was spotted much farther north in Aberdeenshire, marking the area's first sighting of this insect after an absence of over 30 years. This species has a red thorax with bold black-and-white markings on the abdomen.
Mutilla europaea is one of the three types of velvet ant found in the UK © David Cuthbertson via Flickr (CC BY 2.0)
Unusually for a velvet ant, instead of searching out the nests of solitary species to lay their eggs in, M. europaea invades the nests of social species, mostly bumblebees' but also occasionally honeybees'.
The third mutillid species in Britain, Myrmosa atra, belongs to a different subfamily and is not a classic velvet ant, although the female wasps are wingless.
