Native Bee Spotlight: Cuckoo Bees ~ Coelioxys spp.

Cuckoo Bees ~ Coelioxys spp.

A female cuckoo bee, Coelioxys sp. nectars on
hairy false goldenaster, Heterotheca villosa in late fall

There are many types of cuckoo bees in North America. In the Coelioxys genus, there are approximately 46 speces. The common name "cuckoo bee" is typically used for any bee species that lays its eggs in the nests of other bees. These bees are known as cleptoparasites, where the cuckoo bee larvae kill the host larvae and feed on the provisions (pollen and nectar) provided by the host bee.

Coelioxys cuckoo bees are common in the summer months; in central Minnesota I typically see them from June until October. Both males and females can be observed visiting flowers for nectar and females looking for, or waiting to enter a host's nest. These cuckoo bees lay their eggs in the nests of leafcutter bees, Megachile spp. Less frequently, they have been documented laying eggs in the nests of Anthophora, Centris and Euglossa spp.

A female cuckoo bee watches for the
female leafcutter bee to exit the nest
in the rock cavity.

The cuckoo bee flies closer to the entrance
anticipating the exit of the host bee.

Females Coelioxys bees actively look for a host's nest. Once a nest is found, the female cuckoo bee waits until the host bee leaves the nest to collect provisions. With a short window of opportunity, the cuckoo bee slips in the empty nest and looks for a fully provisioned brood cell to lay its eggs in.

The host leafcutter bee, Megachile sp. enters the nest in the
rock cavity carrying a piece of leaf to line or cap the brood cell.

Females have a sharply tapered or triangular-shaped abdomen. This acute point on the end of the abdomen is used to pierce through the layers of leaf pieces that line the brood cells of their host, leafcutter bees. The egg(s) is laid within the layers of leaves, or underneath the pollen mass hidden from sight in case the host leafcutter bee is still in the process of provisioning the nest. The cuckoo bee eggs are often different in size or appearance which may be another reason why the cuckoo bee hides the eggs.

The large sickle-like mandibles that the cuckoo bee larvae use to kill its siblings and host larva.
Illustration from: Michener, C. D. (2000). The bees of the world (Vol. 1). JHU Press.

The menacing part of this cleptoparasitic life cycle occurs after the cuckoo bee larva has hatched and begins to develop. The larva develops large sickle-shaped mandibles that are directed forward (instead of downward) to prepare to kill the host egg or young host larva. By the third or fourth instar, the Coelioxys larva has killed any sibling larvae and the host. It now has an empty brood cell stocked with pollen and nectar provisions to feed on and develop.

A female cuckoo bee nectars on
purple prairie clover, Dalea purpurea

The timing of adult emergence of cuckoo bees is very critical; there is a short window of opportunity to overlap the timing of the host's adult emergence. Coelioxys spp. have been documented emerging slightly earlier or around the same time as their host. A larvae will often develop into an adult the same year as the nest is constructed and more female cuckoo bees are produced earlier in the season.

A female cuckoo bee perches on foliage low to the ground
watching for a leafcutter bee to emerge from a nest in the ground.

Appearance:
Female: Tapered abdomen ending in an acute point
Male: Pronged or multi-spined abdomen
Both Male & Female: Hairs on the bottom of the eyes
Relatively hairless, dark gray - black, often pocked appearance
Many species have red legs

Native plants I have observed Coelioxys spp. foraging on:
Butterfly milkweed, Asclepias tuberosa
Wild Bergamot, Monarda fistulosa
Prairie Coreopsis, Coreopsis palmata
Hoary Vervain, Verbena stricta
Joe Pye Weed, Eutrochium maculatum Smooth Oxeye, Heliopsis helianthoides Black-Eyed Susan, Rudbeckia hirta
New England Aster, Symphyotrichum novae-angliae
Hairy False Goldenaster, Heterotheca villosa
Purple Prairie Clover, Dalea purpurea 

References:
Baker, J. R. (1971). Development and sexual dimorphism of larvae of the bee genus Coelioxys. Journal of the Kansas Entomological Society, 225-235.

Michener, C. D. (2000). The bees of the world (Vol. 1). JHU Press.

Rozen Jr, J. G., & Kamel, S. M. (2006). Interspecific variation in immature larvae of the cleptoparasitic bee genus Coelioxys (Hymenoptera: Megachilidae). Journal of the Kansas Entomological Society, 79(4), 348-358.

Scott, V. L., Kelley, S. T., & Strickler, K. (2000). Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America, 93(4), 941-948.

Wild Geranium Pollinators & Floral Visitors

Like many spring-flowering native plants, wild geranium flowers have the ability to self-pollinate when no pollinators are present. However, the flower matures to ensure cross-pollination when insects are present, with the row of outer anthers developing on the first or second day after the flowers open, followed by the inner row on the second or third day. The stigma becomes receptive after the anthers have dehisced on the third or forth day.

Bees, flies and beetles visit the flower for nectar and pollen. Nectar is secreted from five glands located between the stamens and sepals. In a study by Bertin et al, bees visiting for nectar were responsible for depositing more pollen than pollen collecting bees. Larger bees such as bumble bees and mason bees are considered effective pollinators because pollen brushed onto the underside of their abdomen contacts the stigma. Smaller bees are able to circle around the base of the stamens feeding on nectar without coming into contact with pollen from the anthers above.

Wild geranium flowers are over one inch in width and extremely showy. Dark lines on the flowers act as nectar guides, showing pollinators the location of the nectaries at the base of the stamens.

Small Carpenter Bees, Ceratina spp.
Smaller bee species circle the base of the flower seeking out nectar without coming in contact with the anthers and stigmas above.

Cuckoo Bees, Nomada spp. 
Wild geranium is a nectar source for this cuckoo bee in early spring. Female Nomada bees lay their eggs in the nests of ground nesting native bees, especially mining bees (Andrena spp.). The cuckoo bee eggs hatch and the larvae kills the host bee larvae and consumes the provisions provided by the host. Nomada bees are reddish-brown to black with yellow or white markings.

Mason Bees Osmia spp. 
Mason bees visit wild geranium for both pollen and nectar. Females land on top of the anthers gathering them together with her legs. Pollen is brushed onto the pollen-collecting hairs on the underside of the abdomen. Wild geranium is an important source of pollen and nectar for mason bees, it flowers when females are provisioning their nests.

Sweat Bees Lasioglossum spp.
Sweat bees visit the flowers to feed on nectar.

Fruitworm Beetles Byturus unicolor 
Long, dense hairs cover the elytra of these beetles where pollen grains attach. Adults emerge from the soil in early spring, feed on host plants (raspberries, blackberries and avens), mate, then lay eggs. Larvae burrow into the flower buds and fruit of the host species and buds drop off or decay. Fruit becomes misshapen and ‘wormy’. Look for adult beetles feeding on the pollen of woodland natives in early spring such as Viriginia waterleaf and wild geranium.


References 
Bertin, R. I., & Sholes, O. D. (1993). Weather, pollination and the phenology of Geranium maculatum. American Midland Naturalist, 52-66. Retrieved from: http://www.jstor.org/stable/2426435

Willson, M. F., Miller, L. J., & Rathcke, B. J. (1979). Floral display in Phlox and Geranium: adaptive aspects. Evolution, 52-63. Retrieved from: http://www.jstor.org/stable/2407365

Native Bee Spotlight: Cuckoo Bee ~ Nomada spp.

Cuckoo Bee ~ Nomada spp.

There are many types of native Cuckoo Bees, this Cuckoo Bee falls in the same family (Apidae) as Bumble and Honey Bees.

As the common name suggests, like Cuckoo Birds, Cuckoo Bees lay their eggs in the nests of other bees. In our region, the Cowbird would be a good comparison.

Why go to all the work of collecting pollen and nectar to provision a nest when another bee can do it for you?

I typically see this particular Cuckoo Bee in early spring, from March - May. A cleptoparasite of Mining and Sweat Bees, females sneak in to the ground nests of the host bee, lay 2-4 eggs alongside the host egg. When the first Cuckoo Bee larva hatch it kills its siblings and host egg/larva.

As the Nomada larva develop, it consumes the host bee bread (a combination of pollen and nectar).

Nomada sp. are typically a reddish-brown color with yellow spots, thick antennae and thin legs. The rear legs do not have any pollen collecting hairs because they have no need to collect pollen. If you see Cuckoo Bees visiting flowers, they are only there for the nectar.

Pictured visiting the flowers of Wafer Ash (top), American Bladdernut (middle), and Wild Geranium (left).

Also on spring beauty (left).

I have Mining Bees (Andrena spp.) nesting in the sandy soil of the south slope in our yard. In early spring, several of these Cuckoo Bees will be flying low to the ground landing on sticks and leaf litter seeking out the nests of the Mining Bees.









Source: Attracting Native Pollinators: The Xerces Society Guide, Protecting North America's Bees and Butterflies

Another Native Cuckoo Bee

As you build a healthy landscape with native plants and create and foster wildlife habitat,  you are building a food web which will ultimately attract top tier predators. Top tier predators such as hawks need good nesting habitat as well as an ample food source to feed their young. The same is true for insects. Many insects predate on other insects, so they need their prey to be present as a food source and sometimes for rearing young.

There are many types of cleptoparasitic (Cuckoo) native bees - bees that don't collect pollen and build nests, but instead lay their eggs in the nests of other bee species. The host species' larvae is usually killed leaving the bee bread (pollen and nectar ball) for the Cuckoo Bee to eat as it develops.

The Cuckoo Bee, Triepeolus spp. is a bee that lays eggs in the nests of Long Horned Bees, Melissodes spp. This was the first year that I observed this type of Cuckoo Bee in our landscape. A distinctly colored bee with a black body and white stripes. This particular species has brightly colored orange legs.

Cuckoo Bees will visit flowers for nectar only (no pollen collecting structures). I observed this Triepeolus sp. nectaring on Cup Plant and Hoary Vervain in mid-July.

The Long-Horned bees (host) are ground nesting bees. The female digs a multi-branched tunnel into exposed, sandy soils. The Cuckoo Bee slips into the ground nest and lays its eggs when the female host bee is out foraging for pollen and nectar.

Read more about other Cuckoo Bee sightings in our landscape:

Nomada sp.
Cuckoo Leafcutter Bee, Coelioxys sp.
Coelioxys sp.
Nomada sp.

Hoary Vervain Insect Visitors

Hoary Vervain ~ Verbena stricta


I planted more Hoary Vervain a few years ago in our landscape because it likes dry, sandy locations in full sun. Now, I'm enjoying a significant increase in the diversity of pollinators and insect visitors coming to Hoary Vervain.

Small Skipper Butterflies like the tubular five-parted flowers. Pictured here, Peck's Skipper (Polites peckius), one of the easier small skippers to identify with its distinct markings.

A second Skipper, my best guess is Fiery Skipper (Hylephila phyleus), although we are a little north of its range. Perhaps due to our early spring warm-up this Skipper got a head start on its migration north and traveled a little further.

Cabbage White butterflies (Pieris rapae) are also frequent visitors seeking out nectar.

Hoary Vervain flowers from the bottom upwards, on the tall narrow flower spike. The flowering time can therefore last from July into September providing a nice source of nectar for insects.

Some of the first Soldier Beetles in our yard this season are on Hoary Vervain. They like to feed on both nectar and pollen on many types of flowers.

Soldier Beetles are predators of other insects and are therefore considered natural enemies. Falling in the family Cantharidae, some soldier beetle adults will feed on aphids, and insects eggs and larvae providing biological control.
(Michigan State University, Natural Enemies)

This attractive, large Syrphid fly was using its long mouthpart to sponge up some nectar.

Syrphid flies are also predators, some larvae feed on aphids.

Bumble Bees also like the Hoary Vervain flowers. Less frequent visitors, probably because some preferred native species such as Wild Bergamot flower at the same time.

These medium-sized fast moving Long Horned Bees (Melissodes species) would stop on the Hoary Vervain just long enough so I could snap a photo.

This particular bee likes to fly around other bees nectaring and take small jabs at them. They seem to spend their time doing this more than landing on flowers for pollen or nectar.

Two of the new bee species discoveries this season have occurred on Hoary Vervain.

This Cuckoo Leafcutting Bee (Coelioxys species) is a cleptoparasite of Leafcutter Bees. With no means to collect pollen, its only visiting the Hoary Vervain for nectar. Read more about the Cuckoo Leafcutting Bee here: Another New Native Bee Discovery.

The second discovery, just last week was another Cuckoo (cleptoparasitic) Bee in the Genus Triepeolus. With bright orange legs and black and white striped body, it is an extremely attractive bee.

These bees lay their eggs in the nests of Long-Horned Bees (Melissodes species).

If you have an open, sunny location with medium to dry soils, I highly recommend Hoary Vervain. Its upright stature, coarse leaves and long blooming purple flowers make it a great addition to any landscape or prairie.

Another New Native Bee Discovery

Leafcutter Bee

I'm amazed at the number of new native bees we've seen this year in our yard. Many of the new ones are cleptoparasites on other bee species, otherwise known as Cuckoo Bees.

Read earlier posts here about Nomada Cuckoo Bees, and another post about a Sphecodes Sweat Bee that's also a Cuckoo Bee - both new sightings this year.

The latest new bee is a cleptoparasite of Leafcutter Bees (Megachile species). Leafcutter Bees are different from other native bee species - instead of collecting pollen on their leg combs, they collect pollen on hair patches on their abdomens.

Leafcutter bees nest in cavities or hollow stems. Females cut circular pieces of leaves to wrap brood cells. The cell's sides are made with oval pieces, and it is closed with a number of circular pieces. (Attracting Native Pollinators)

This week I photographed this new Cuckoo Bee (Coelioxys species) nectaring on Prairie Coreopsis and Butterfly Milkweed. I thought it could be a type of wasp at first, with its pointed abdomen.

These Coelioxys Cuckoo Bees are in the same family as Leafcutter Bees (Megachilidae). Like the other Cuckoo Bees I wrote about this spring, they don't have any pollen collecting capabilities. They visit flowers for nectar only.

"Protruding from the last segment are short spines used to break through the brood cell walls of their host species during egg laying".

"The female enters a nest while the host is foraging and hides her egg by laying it in the wall or behid the food masses of almost finished brood cells." (Attracting Native Pollinators)

Like other cleptoparasites, the larvae of the Cuckoo Bee hatch and kill the host bee larvae. They then eat the pollen supplied by the host bee.

It has been fascinating to observe the order of arrival of native bees in our landscape. Starting with common Bumble and Mining Bees, the next season Leafcutter, Digger, Carpenter and Sweat Bees, then this year Carder Bees and many types of cleptoparasitic Cuckoo Bees.

It's a Bee Eat Bee World

A couple of weeks ago I wrote about the early spring pollinators on Bloodroot and Pasque Flower.

I photographed many bees, one I didn't write about was the Cuckoo Bee (Nomada ruficornis species group) pictured here on the left. These small rusty brown colored bees are thieves of sorts, otherwise known as kleptoparasites.

They lack any kind of pollen transport structure so they rely upon other bee species to do their pollen collecting for them.

The Mining Bees (Andrena species) were the most common visitors of the Bloodroot flowers and these are one type of bee species that the Cuckoo Bee preys upon.

The Mining Bees collect and stock their ground nest with pollen which they lay their eggs upon so the hatching larva can consume the pollen.

Andrena bee in foreground, Nomada bee behind

"A Nomada female will slip into a host's nest and stick her eggs into the wall of the host's larval cell before the host has finished stocking it with pollen. When the host (usually an Andrena bee) finishes stocking her cell and lays her egg in the nest, the Nomada larva will kill the host's egg and take over the nest, like a cuckoo chick in a bird's nest." (Insects Their Natural History and Diversity)

Cuckoo Bee

Having Cuckoo Bees present in our landscape is in my opinion a good indicator of ecological health and biodiversity.

It indicates that we are providing the right types of flowering native plants and nesting sites so that Andrena and other solitary native bees can successfully build nests and rear young (except for the ones taken over by the Cuckoo Bees of course).