Meet the cuckoo bees

Vestal cuckoo bee by Chris Gomersall/2020VISION

You may have heard or even seen a cuckoo during spring, but have you seen a cuckoo bee? Learn all about these fascinating insects and pick up some handy ID tips.

It might be so tiny you barely notice it, but the insect world is anything but boring. Playing out like a soap opera, life, death, murder and duplicity are all part and parcel of the natural world’s rich insect tapestry. Some of its craftiest and most interesting characters are the UK’s cuckoo bees, which use clever mimicry and bare-faced cheek to raise the next generation.

What is a cuckoo bumblebee?

A cuckoo bumblebee is a ‘cleptoparasite’ of other bumblebee species. This means that, much like the cuckoo bird, it takes over the nest of its host species. A female cuckoo bumblebee enters the nest of its host and kills the queen. She then establishes herself as the new ‘queen’, being waited on by the host workers, and lays her own eggs to be reared by them.

Bumblebees aren’t the only cuckoos, however. Other cuckoo bees, like nomad bees, also parasitise bee nests, as do insects that aren’t bees at all.

A vestal cuckoo bumblebee feeding from a knapweed flower

Vestal cuckoo bee by Charlotte Varela

What does a cuckoo bee look like?

That all depends on the cuckoo. Cuckoo bumblebees, for example, have evolved to look like their hosts so they can take over host nests without arousing suspicion. Nomad bees (a cuckoo of solitary bee species), on the other hand, look more like tiny wasps.

Where do cuckoo bees live?

Cuckoo bees can be found right across the UK, though some species are rarer in certain areas. From woodlands and heaths to urban areas and gardens: where the host species lives, you have a chance of seeing a cuckoo bee.

What do cuckoo bees eat?

Cuckoo bees drink nectar from flowers, and the females eat pollen to help develop their ovaries. However, being cleptoparasitic means the hard work ends there and they don’t collect pollen to take back to the nest. This is left completely up to the host workers.

The cuckoo bee larvae themselves eat any existing pollen balls left for the host larvae, as well as new pollen stocks brought to them by the host workers. If the female cuckoo bee hasn’t already done so, they’ll kill and eat the host larvae too.

Common cuckoo bumblebees

Cuckoo bee identification isn’t always easy, especially when it comes to cuckoo bumblebees as they look so similar to their hosts. Some of the key things to look out for in cuckoo bumblebees are:

  • A lack pollen baskets on their legs.
  • Dark-tinted wings.
  • Less dense hair with a shiny thorax and abdomen showing through.

Here are some of the most common cuckoo bumblebees in Lancashire, Manchester and North Merseyside.

Vestal cuckoo bee (Bombus vestalis)

A vestal cuckoo bee drinking nectar from a knapweed flower

Vestal cuckoo bee by Chris Gomersall/2020VISION

Though traditionally a common southern species, the vestal cuckoo bee has made its way further north in recent years and isn’t uncommon in our region. The females’ host of choice is the buff-tailed bumblebee, and they’re most commonly found feeding from sallow catkins and dandelions, or investigating the ground in search of buff-tailed bumblebee nests. Male vestal cuckoo bees like feeding from thistles, brambles, knapweeds, and garden plants like lavender in late summer.

ID tips: Yellow collar on the thorax and a white tail. There are large yellow patches on either side of the abdomen, above the tail. Males sometimes have a faint yellow band at the top of the abdomen.

Red-tailed cuckoo bee (Bombus rupestris)

A red-tailed cuckoo bee feeding from a knapweed flower

Red-tailed cuckoo bee by Charlotte Varela

It isn’t hard to guess who the red-tailed cuckoo bee uses as its host… that’s right, the red-tailed bumblebee! Female red-tailed cuckoo bees are impressive insects – our largest cuckoo bee, with the greatest wingspan of any British bumble. They can be seen from late spring, slowly and deliberately patrolling grassy banks for host nests. They feed from flowers including dandelions, comfrey and bugle earlier in the year, with new summer females visiting spear thistle, teasel and knapweeds.

ID tips: Black with a red tail. Females have very dark, almost black wings. Males have largely undarkened wings but can be separated from red-tailed bumblebees by greyish-yellow banding and a lack of yellow facial hair.

Forest cuckoo bee (Bombus sylvestris)

As its name suggests, the forest cuckoo bee is the most common cuckoo of woodlands. It parasitises the early bumblebee, with females usually appearing in April before a second brood in June. These second generation females can be seen on early autumn flowers like devil’s-bit scabious and ivy. Male forest cuckoo bees have a special quirk – they produce a mousy scent that no other Bombus species does.

ID tips: Females have a broad yellow collar, an indistinct yellow band on their abdomen, and a white tail with a small black tip. This tip is orange in males. Females also have a characteristic stance, with the tip of their abdomen very curled-up underneath themselves.

Gypsy cuckoo bee (Bombus bohemicus)

Though it can be quite variable, the gypsy cuckoo bee looks similar to its host, the white-tailed bumblebee. They aren’t too fussy; living in a wide range of habitats and feeding from lots of different flowers. Females usually emerge from hibernation in April or May, while new males and females emerge in July and August.

ID tips: Yellow collar on the thorax and a white tail. There is a small pale yellow patch on each side of the abdomen, above the tail. Males often have a second yellow band at the rear of the thorax.

Field cuckoo bee (Bombus campestris)

This cuckoo of the common carder bee is another generalist when it comes to habitat; found in a range of settings and nectaring on a variety of flowers. Females emerge from their winter slumber around late April, while males and new females are on the wing from July to September.

ID tips: Very yellow in appearance, with a yellow stripe at the top and bottom of the thorax, and yellow patches on the sides of the abdomen that can be so extensive in males that their whole abdomen looks yellow. Females have a particularly shiny abdomen.

Common nomad bees

Many nomad bee species are frustratingly difficult to identify, having just one or two features that distinguish them from one another. Here are a few of the most common species you’re likely to see in our region.

Gooden’s nomad bee (Nomada goodeniana)

This largish nomad bee is a cuckoo of the buffish mining bee, so can usually be found not far from the nest site of its host. It typically flies from April to June, flying slowly over short vegetation and bare ground in sunny spots. Gooden’s nomad bee looks really similar to Marsham’s nomad bee, but the latter’s first yellow abdominal band is either absent or very faint, while the second is separated into two parts.

A Marsham's nomad bee resting on a stone wall

Marsham's nomad bee by Charlotte Varela

Marsham’s nomad bee (Nomada marshamella)

Marsham’s nomad bee parasitises the nest of the chocolate mining bee. As well as being hard to distinguish from Gooden’s nomad bee, it also looks like the painted nomad bee. To tell them apart look out for two yellow spots at the base of the thorax (painted nomad bees have one), and red tegulae (the nodule at the base of each wing). Painted nomad bees have yellow tegulae.

Flavous nomad bee (Nomada flava)

The poor chocolate mining bee doesn’t have much luck – it’s also the main host of the flavous nomad bee. This Nomada cuckoo bee is a little more distinctive than its cousins, with reddish markings on its thorax and the top of its abdomen. Like most nomad bees, you’re most likely to spot the flavous nomad bee flying over short vegetation and bare ground in the sunshine.

Other bee parasites

Not all bee parasites are actually bees. In fact, there is a diverse community of insects that are dependent on bees to complete their reproductive cycle. Here are just three of them.

A dark-edged bee-fly resting on a bee ID guide at Seven Acres Nature Reserve

A bee-fly checking out the furry competition. Photo by Adam Berry

Dark-edged bee-fly (Bombylius major)

The dark-edged bee-fly is our most common bee-fly. Though it looks like a fluffy bumblebee, it is actually a kind of fly that employs clever mimicry to allow it to get close to mining bee nest holes. Once there, it coats its behind in a layer of dirt to add some weight to its eggs, and flicks them close to the mining bee nest hole with an impressive forward swing of its dumpy body.

Once a bee-fly larva hatches, it crawls deep into the nesting chamber of the host bee to develop. When it’s large enough, it attaches itself to the host larva and sucks out its bodily fluids.

A ruby-tailed wasp resting on a wall

Ruby-tailed wasp by Charlotte Varela

Ruby-tailed wasp (Chrysis ignita)

This species of ruby-tailed wasp is another mining bee parasite. Close up, its bright, shimmering body looks like an intricate piece of hammered jewellery, but this tough exterior has evolved specifically to help the wasp sneak into other bees’ nests to lay its eggs. The incredibly hard body cuticle protects against stings if the host bee discovers it trespassing in the nest chamber, and the ruby-tailed wasps abdomen is concave underneath, allowing it to roll into a ball if threatened.

A bee moth resting on stone

Bee moth by Philip Precey

Bee moth (Aphomia sociella)

Surprisingly, there are even moths that use bees as hosts for their larvae. The bee moth lays its eggs in the nests of bumblebees and social wasps. When the larvae hatch, they feed on the wax, pollen, nectar, honey, dead insects and even live larvae inside. Male bee moths are a little showier than the females, with brighter purple, green and red tones to their wings.

We hope this fascinating insight into the world of cuckoo bees has you searching every flower, grassy bank and wall for these intriguing insects. If you manage to spot one we’d love to see your pictures. Why not share them with us on one of our social media pages?