Spring has sprung, and the season is in full swing. While bragging over your prized rose, you notice small circular rings in the leaves of your rose bush. It’s Leafcutter bee season again.
Leafcutter bees are solitary and moderately sized bees. They are aptly named due to the process of cutting pieces of leaves for nesting material. The females are black with grey-colored hairs on the abdomen used for collecting pollen. Larger than the males, they tend to their own broods.
Bees are beneficial little pollinators that help pollinate gardens, crops, and orchards, but not all bees are the same. There are thousands of varieties, with each having its very own unique benefits. Leafcutter bees are no exception.
Leafcutter Bees
Small circular segments of leaves have been cut away on the leaves in your garden shrub. This is a sign of leafcutter bees buzzing about. But is it really such a big issue for your plant? Although your shrubs may look like Swiss cheese, there are several benefits to having these little buzzing creates about.
How To Identify A Leafcutter Bee?
Leafcutter bees are part of the Megachilidae genus and form part of 630 different bees species in the United States. Globally, this genus has been reported with more than 4000 species. These include bees that use leaves and flower cuttings to build their nests.
Subdivided into the group megachili, leafcutter bees, these genera make up over 1500 species of bees that cut up segments of leaves as a building material for their nests.
Most of the 630 species are native to the United States, with a few introduced from Europe, accidentally or not. The Alfalfa leafcutter bees were introduced to the United States from Europe and are rightly named as they are the main pollinators of alfalfa plants.
Although each genus has its own slightly different characteristics that set them apart from others, they are all solitary bees that tend to their own brood.
Another similarity between them is the scopa hair, which holds the collected pollen in place during flight. These hairs are found on the underside of the abdomen section of the bee, making them stand out from the rest.
When their scopa is filled with pollen, you immediately notice the bright golden yellow abdomen.
Female leafcutter bees are robust and similar in size to their honey bee counterparts.
- They have black bodies with light brown hair
- Have triangular abdomens ending in a point.
- Scopa hairs for collection of pollen
- Possess a stinger that they rarely use
- Have black eyes
- Strong mandible jaws for cutting leaves
- Shorter antennas than their male peers
Male leafcutter bees are a bit more difficult to identify as they are smaller than the female with a bit more of a fluffy appearance to the female.
- Fluffier look than the female with more hair around the thorax and between the abdomen sections
- Lack of the bright yellow scopa that females have
- Rounded abdomen
- Longer antennas than females
- Green eyes
- No stinger
- Long hair on the forelegs
| Leafcutter Bee Characteristics | |
| Habitat | Grasslands, heathlands, moorlands, farmlands, woodlands, towns, orchards, and gardensWidespread through America |
| Life cycle | Females can live up to 2 months, Males live between about 1 and 2 weeks but die after mating with females |
| Generations | Possibility of 2 generational broods |
| Nesting material | Uses circular discs of 6 to 13mm size from soft, flexible deciduous plants |
| Food | Eats nectar and collects pollen on flowers, fruit trees, and nut trees |
| Activity period | Early spring to fall (March-June) |
| Description of female | Similar in size to the honeybee Species range from 10-20 mm in lengthLarge, strong mandible jawsBroadheadsCarry pollen under the abdomen with scopa hairs giving them the appearance of a bright yellow abdomenTriangular abdomen ending in a pointUpturned carrying position of their abdomenShe has a stinger, although she rarely uses it |
| Description of male | Slightly smaller than the femaleNo mandible jaw for cutting leavesDo not have scopa hairs on the abdomenVery hairy front legsRobust round abdomenNo stinger |
| Color of female | Black smooth body with light-grey to light yellow abdomen hairs |
| Color of male | Black with more silver-grey hairs visible on the body, giving it a fluffier appearance |
Do Leafcutter Bees Pollinate?
Due to the high efficiency of pollination, these little bees are getting increased recognition for their pollination and have become progressively popular with beekeepers to pollinate crops and orchards.
The females collect dry pollen that is stored on the underside scopa. As they move from blossom to bloom, the pollen is easily transferred. They are also super-efficient little workers as they pollinate flowers within 300 feet of their nests and can visit 80 different plants.
Alfalfa leafcutter bees are fantastic pollinators and are the second oldest managed bees in the US. Used for the pollination of alfalfa plants and many other legumes that consist of a large central petal with two side petals, they also have a bottom fused petal called a keel. This keel protects the stamen containing pollen inside the flower, and only when the petal is triggered or a bee lands on it is the stamen released, allowing the pistol to hit the bee in the head to expose the pollen.
This pollination does not seem to deter the leafcutter bee compared to the honey bee, which has no interest in this kind of flower. This makes the leafcutter bees fantastic and a much-needed pollinator for legumes and other crops.
The male leafcutter bee has little value as a pollinator. They do not actively collect pollen for storage or nest and only really eat nectar and some pollen to sustain their energy. Their sole purpose and reason for emerging earlier than the females is to mate with them and then die.
The female leafcutter is the main pollinator as they visit several flowers to collect nectar and pollen to fill the individual cells that she is building for her brood.
What Plants Do Leafcutter Bees Need?
Apart from needing flowers for collecting nectar and pollen, leafcutter bees also need a range of soft, flexible leaves to build their nest. Like the ornamental rose and lilac plants, any broadleaf deciduous plants will do. Wildflowers, such as clover, Black-eyed Susan, and buckwheat, are also great plants for the bees to forage for nesting supplies.
They will cut small circular discs about ¼ of their body and fly them back to the nests to build the cells they need to lay their eggs.
Although your plant’s leaves may look like someone fired a gunshot shot at them, this process does not harm your plants, and it is only the aesthetic part of your flower that has been damaged.
Leafcutter bees do not use the flower or petals to create nests. They will only use the pollen and eat the nectar of the flower. Using pesticides will only harm the bee and cause more decline in the population of bees. Rather use a fine cheesecloth or mesh to protect your prized plants from the Swiss cheese syndrome.
Bringing native plants into your garden will also help offer a diverse range of food for the bees. These plants are less vulnerable to pests, and therefore you will need to use fewer pesticides that are harmful to pollinators.
What Do Leafcutter Bees Eat?
Although leafcutters cut little discs out of your flower’s leaves, they do not eat this part of the plant at all. The leave is purely there to build the nest and prevent pests and predators from harming the larvae in the nests.
Leafcutter bees eat nectar from the plant and some pollen. The pollen is also greatly used to supplement the cells for the larvae to feed on once it hatches.
Leafcutter bees enjoy a variety of plants that they can forage and feed on. A buffet of colors is essential to pique the bee’s interest and to have a continued supply of blossoms throughout spring, summer, and autumn.
| Flower | Season | Color | Hardiness zone | Native to the US |
| English bluebell Currant Primrose Blue-violet Wood anemone Alyssum VervainsBlazingstarSwamp milkweedFoxgloveCampanulaSea hollyCrabapple treeGoldenrodCommon sunflower Honeysuckle(northern bush) | SpringSummerSpring/summerSpring/summerSpringSpring/SummerSpring/SummerSummerSummerSpring/SummerSummer/FallSummer/FallSpring/Summer/FallFallSummerSummer | BluePale green flowersYellow/Pink/WhiteBlueWhiteWhitePink/PurplePurpleLilacBrown/Yellow/OrangeViolet blueSilver bluePinkYellowYellowYellow/Orange | 4-103-73-84-95-82-115-93-93-114-84-92-84-83-92-113-7 | O PP PPPPP P P |
What Is A Leafcutter’s Habitat?
Leafcutter bees are found in habitats where they can easily find an abundance of flowers and plants for foraging and nest materials.
You can find Leafcutter bees using a variety of nesting substrates which include,
- Hollow plant stems
- Abandoned wood-boring insect nests or burrows
- Small cavities in stones, houses, earthen banks
- Soft, rotted wood
- Man-mad bee hotels
Leafcutter bees can be found in a wide range of habitats such as varied deserts, coastal dunes, prairies, meadows, shrublands, woodlands, and gardens where there is an abundance of nectar and pollen plants nearby for nesting possibilities.
Is Leafcutter Bees Native To America?
There are about 630 species of the Megachilidae genus that are native to the United States. Like the Alfalfa leafcutter bee, a few of them were brought onto the continent either by mistake or on purpose.
Life Cycle Of Leafcutter Bees
The life cycle of leafcutter bees is similar to other solitary bees. As the winter ends and temperatures increase, the pupae start to emerge as fully-fledged bees.
Males are the first to exit the nest. While they wait 2 to 3 days for the females to emerge, they will be the first buzzing you will see around your blossoms.
Once the females emerge from their cocoon, the males will jump on their backs before they have had a chance to fly off and attempt to mate with the females to fertilize them.
Once the female has accepted the male and is ready to mate, she will lift her abdomen and retract the stinger allowing the male to deposit his sperm into a spermatheca.
Once the female is finished mating, she will look for an appropriate nest for her brood and start collecting pollen and feeding on nectar until her ovaries have matured and she is ready to lay her eggs.
Once she finds an appropriate nest, she will perform an intricate zig-zag dance in front of the nest in order to orient herself with her surroundings and to be able to recognize the nest when she comes back from her foraging.
If the nest is moved after she has familiarized herself with her surroundings, she will be disorientated and will abandon the work she did and try to find a new viable option for her nest.
Once she has fed on some sweet nectar from nearby flowers, she will start to forage for soft leaves to build her nest for her brood. Leafcutter female bees will use their strong mandible jaws to cut small circular discs out of leaves of about 0.25 to 0.50 inches in diameter and carry them back to their nests.
In the nest, the female bee will layer the first leaves at the end of the nest as a protective barrier against possible intruders or pests and act as a barrier against outside weather conditions. This requires roughly about 15 discs to create the initial wall.
Once the outside wall has been formed by laying discs and sticking them together with saliva, she will start to forage for the nectar and pollen that will form a paste, which will be the food source for her larvae in that cell. This process can take several hours and will require many trips to gather the required amount of pollen.
Once she is satisfied with the cell, she will then lay the first of her eggs. This single larva will occupy the cell for the duration of its growth. The female bee determines the sex, and females will always be placed in the back cells or be the first eggs laid.
The female Leafcutter bee will take one of her eggs and mix it with the stored sperm in her spermatheca to create a female larva. When she reaches the cells for males, she will deposit an egg that has not been fertilized with sperm.
Once the leafcutter bee has laid her egg has been laid, she will seal off the cell with more leaf discs, and the process will repeat itself until she has filled her nest with individual cells. At this point, she will cap the entrance on the nest to protect her nest from pests and predators.
The nest resembles a cigar tube that contains, on average, 8-10 cells per nest. A female leafcutter bee lives about two months and can finish 2 to 4 nests in her lifetime. Now I know where the term busy bee comes from.
The Leafcutter bee female determines the amount of female versus male eggs depending on the depth and width of the nest. A deeper tunnel favors the production of female eggs. Under good conditions, the sex ratio is about 1.5 to 2 males to females per nest.
The Development Of The Leafcutter Larva
The development of leafcutter bee larvae is dependent on the temperatures. Warmer temperatures that reach daily highs of 84°F will allow the larvae to develop in about 20 days. Lower temperatures that reach a maximum of 70°F will cause the larvae to take about 42 days to develop into adult bees.
If weather conditions are favorable and temperatures remain warm for a longer period of time, then there is a possibility of a second-generation brood.
During late summer and early fall, the eggs start to hatch,
- Larva starts to feed on the egg yolk
- Larva starts to feed on the pollen loaf that is in the cell
- The larva develops by going through 4 growth stages called instars
- By the 4th stage, the larva has consumed all the pollen in the cell
- It then starts to spin a silk cocoon inside the cell
As the temperatures start to fall during the fall season, the prepupae in the cocoon will stop developing and overwinter until temperatures start to rise again.
The pupae remain dormant during the winter season in anticipation of the warmer season.
During the spring season, as the temperatures start to rise,
- The prepupae molts into a pupae
- At this stage, they resemble a bee but remain completely white
- Over the next few days, the pupae start to change color
- One week after darkening, they will have transformed into a fully-fledged bee
- Within a few days, the first males will start to emerge
- Within 2-3 days after the males emerge, the females emerge
If temperatures remain warmer for longer, a second generation is possible within the same season.
What Are The Problems With Second Generation Leafcutter Bees?
Second-generation leafcutter bees can be an added benefit for pollination, depending on when they emerge. Should the temperatures be optimal and the eggs hatch within the first 22 days, a second-generation may emerge 1 ½ month (mid-summer) from when the first generation brood emerged.
Unfortunately, this generation can face some difficulties as they emerge later in the season.
- They have fewer foraging possibilities available to them
- They will produce fewer nests and eggs as they have less time than the first generation in early spring.
- Their larvae must develop late in the season and finish their pollen loaf before it is too cold for them to feed before overwintering.
- Chalkbrood disease peaks in colder weather conditions, creating a higher possibility of chalkbrood disease for their larva.
Can You Buy Leafcutter Bees?
In today’s time, you can easily buy leafcutter bees online from bee farms that collect cocoons and overwinter them in the perfect conditions to ensure the larva inside are healthy and will mature when the conditions are right.
Buying leafcutter bees is not the same as buying honeybees. When buying a leafcutter bee, you are, in fact, buying the individual cocoons. As they are released in late spring-early summer, it is important to buy your leafcutter bees at the right time, generally between May and August.
When it’s time to release your bees, place them near the nesting house or on top of the nesting tubes. Once they emerge, they will find their own appropriate nesting tube. Ensure they are out of direct sunlight and rain and that no predators can feast on them.
It is best to release the leafcutter cocoons when daytime temperatures are consistent at about 75 °F, and the spring buds have blossomed. Once the temperature conditions are right, the cocoons will begin to hatch, and the bees will emerge between 1 and 10 days. In unfavorable conditions, it may take up to 3 weeks.
Conclusion
As part of the Megachilidae genus, the Leafcutter bee forms part of a large group of bees with similar qualities and habits. Each genus varies slightly from the next. This solitary little bee is independent of the other bees of its species and tends to its own nest, foraging, and brood.
As its name describes, the leafcutter is a bee that cuts circular discs to form a cigar-looking tube of nests for its brood. This species can produce two generations of bees depending on the weather conditions, allowing for late-season pollinations of crops and plants.
A busy little bee that is an ideal pollinator of tubular flowers with hard-to-reach pollen makes them an appropriate choice for beekeepers to help pollinate crops such as alfalfa and other crops that honey bees will not touch.
References
- https://www.houzz.com/magazine/put-out-the-welcome-mat-for-leafcutter-bees-in-your-garden-stsetivw-vs~44339121
- https://onlinelibrary.wiley.com/doi/full/10.1111/ddi.12709
- https://www2.gnb.ca/content/gnb/en/departments/10/agriculture/content/bees/alfalfa_leafcutterbees.html
- https://www.thespruce.com/leafcutter-bees-in-your-garden-5120866#toc-why-leafcutter-bees-are-important-pollinators
- https://www.bumblebeeconservation.org/patchworkleafcutterbee/
- https://content.ces.ncsu.edu/leafcutter-bees
- https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/megachile_bees.shtml
- https://www.buzzaboutbees.net/leafcutter-bee.html
- https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/bees/leaf-cutter-bees.aspx
- https://entnemdept.ufl.edu/creatures/misc/bees/leafcutting_bees.htm
- https://en.wikipedia.org/wiki/Megachilidae
- https://en.wikipedia.org/wiki/Megachile
- https://www.ars.usda.gov/pacific-west-area/logan-ut/pollinating-insect-biology-management-systematics-research/docs/pollinatormain/
- https://www.natureserve.org/sites/default/files/web_-_leafcutter_bee_report_brochure.pdf
- 12 plants to entice pollinators to your garden | OSU Extension Service (oregonstate.edu)
- A-List of Plants That Attract Bees – Backyard Beekeeping (iamcountryside.com)
- Giving Your Garden a Bee-utiful Boost – FineGardening
- Leafcutter Bees (colostate.edu)
