Alfalfa leafcutter bee facts for kids
Quick facts for kids Alfalfa leafcutter bee |
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| Scientific classification | |
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Megachile
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| Species: |
rotundata
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The alfalfa leafcutting bee, Megachile rotundata, is a fascinating insect from Europe. Now, it's found worldwide. Unlike honey bees, these are solitary bees; they don't build colonies or store honey. Each female builds her own nest. They are amazing pollinators, especially for alfalfa plants. Farmers use them to help crops like carrots, other vegetables, and fruits grow. They get their name because they cut leaf pieces to line their nests. These bees eat pollen and nectar. Female and male bees look a bit different, called sexual dimorphism. While they can bite or sting, they are usually harmless, with a sting much less painful than a honey bee's.
Contents
- Discovering the Alfalfa Leafcutting Bee's Family Tree
- What Does an Alfalfa Leafcutting Bee Look Like?
- Where Do Alfalfa Leafcutting Bees Live?
- The Amazing Life Cycle of the Alfalfa Leafcutting Bee
- How Alfalfa Leafcutting Bees Interact with Their World
- Why Alfalfa Leafcutting Bees Are Important to Humans
- See also
Discovering the Alfalfa Leafcutting Bee's Family Tree
The Megachile rotundata, or alfalfa leafcutting bee, belongs to the Megachile genus. This group is famous for bees that cut leaves to build their nests. It's part of the large Megachilidae bee family, with over 4,000 species!
What Does an Alfalfa Leafcutting Bee Look Like?
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These small leafcutting bees are about 6–9 mm (0.24–0.35 in) long and dark grey. They can sometimes have two generations in one year.
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Males and females look different. Females have white hairs all over, including special hairs on their bellies for carrying pollen. Males are smaller and have white and yellow spots on their abdomens.
Where Do Alfalfa Leafcutting Bees Live?
Originally from Europe, Megachile rotundata is now found on every continent except Antarctica. People brought them to places like North America, New Zealand (1971), and Australia (1987). They help pollinate important food crops, especially alfalfa. Now, they live freely in the wild in many of these new places.
Building a Cozy Home: Nest Construction
Female alfalfa leafcutting bees are expert builders. They make tube-shaped nests in rotting wood, hollow stems, or even soda straws. In nature, they use small holes or cracks in trees. Farmers provide paper tubes or drilled wooden blocks for them to nest in. Their nests are a string of small rooms, called cells. Each cell is made from about 15 round leaf pieces, cut with the bee's strong mouthparts. This creates a thimble-shaped cell. Inside, the female places a ball of pollen and nectar for her baby. She puts nectar first, then pollen from her scopa. Each cell gets one food ball and one egg. After laying an egg, she seals the cell with more leaf pieces.
Smart Nest Planning: Cell Size and Bee Babies
Female bees are clever about where they lay eggs. They often place eggs that will become females in the inner cells, and eggs for males in the outer cells. Female bees need more food to grow, so the mother bee puts more food in cells meant for females. The size of the nest tunnel also influences the number of male or female bees born. The mother bee controls this balance.
How Bees Find Their Way Home: Nest Recognition
Female bees leave special chemical smells on their nests as they build them. These smells are strongest near the entrance. Scientists found that without these smells, bees couldn't find their own nests. This shows how important these chemical "scents" are for them.
The Amazing Life Cycle of the Alfalfa Leafcutting Bee
Alfalfa leafcutting bees have a special way of developing, called haplodiploidy. Males come from unfertilized eggs, females from fertilized ones. Adult bees emerge in two ways. Some larvae grow quickly and become adults by summer's end. Others enter a resting phase called diapause through winter, emerging the next spring. A baby bee, or larva, goes through four growth stages. It eats its food ball, then enters diapause. It spins a silky cocoon. In spring, the larva changes into a pupa. Finally, the bee chews its way out. After emerging, females usually mate and start building nests a week later. Summer-emerging bees are often mostly males. Spring-emerging bees are more often females and usually bigger, needing more food for winter. The distance a mother bee flies for food also affects her babies. Farther flights tend to result in more male offspring.
Emerging from the Nest: Sibling Competition
When bees are ready to emerge, it can be a challenge. A bee in an inner cell might be ready, but another in an outer cell might still be resting. The inner bee can try to go around, wait, or, if delayed too long, chew through the cell in front. This can sometimes harm the bee inside. Male bees often bypass other nests more easily because they are smaller.
How Alfalfa Leafcutting Bees Interact with Their World
What Do They Eat?
Alfalfa leafcutting bees love nectar and pollen, especially from alfalfa plants. Females start eating right after emerging for energy to lay eggs. They use their long tongue, a proboscis, to feed. Pollen sticks to their special carrying hairs as they feed.
Who Are Their Enemies? Predators and Parasites
Alfalfa leafcutting bees have many enemies, about 28 different species. These enemies have clever ways to attack their nests. One tough predator is the Trichodes ornatus beetle. Female beetles lay eggs in tiny cracks in the bee's nest. Their larvae eat the baby bees and their stored pollen food. Other beetles, like Trogoderma glabrum and Trogoderma variabile, also attack. Their larvae eat the developing bee larvae or pupae.
Tiny Invaders: Parasitic Wasps
Wasps are the main parasites. A parasitoid wasp, Pteromalus venustus, is a big threat. The female wasp stings a developing bee larva or pupa to paralyze it. Then, she lays her eggs on the bee's body. Her babies grow by feeding on the bee. Other parasites include Coelioxys wasps. They sneak into a bee's nest when the mother bee is away. They lay their own eggs. The Coelioxys larva then kills the baby leafcutting bee and eats all its food. Another parasite, Nemognatha lutea, lays eggs on flowers. A tiny N. lutea larva hitches a ride on a bee. It travels back to the bee's nest. Once inside, it eats all the stored food.
Bee Health: Diseases
Alfalfa leafcutting bees can get sick. Chalkbrood disease is common, caused by a fungus called Ascosphaera aggregata. The fungus enters the nest through pollen and nectar. When a larva gets chalkbrood, its body can turn milky. It might develop pink, tan, or gray spots. Dark fungal growths can appear under its skin. To fight chalkbrood, farmers clean nests. They use special methods like paraformaldehyde fumigation to keep bees healthy.
How Do They Protect Themselves?
Female alfalfa leafcutting bees have stingers. But both males and females usually use their strong mandibles to defend themselves. They only bite or sting if threatened or squeezed. Farmers don't need special bee suits. If a bee does sting, it doesn't lose its stinger, so it can sting more than once.
Why Alfalfa Leafcutting Bees Are Important to Humans
Helping Farmers: Pest Control
Farmers work hard to protect these helpful bees. They use special methods to keep pests away from the bee nests. For example, they use strips or ultraviolet lamps to kill harmful parasites without hurting the bees. Farmers also use physical barriers like thick walls or felt cloth around nests. This stops parasites from getting inside. Another way to help is by carefully opening nesting materials and cleaning cocoons to remove pests.
Super Pollinators for Our Food
The alfalfa leafcutting bee arrived in the United States by accident in the 1940s. It became a great helper! Farmers learned to use them to help crops produce more seeds. They are excellent pollinators for plants like:
- Alfalfa
- Other Legumes (peas, beans)
- Rapeseed
- Clover
- Blueberryes
These bees are useful because they often nest close together. They use human-made nesting materials. They are very good at pollinating alfalfa. Plus, they emerge as adults just when alfalfa flowers are ready. Farmers receive these bees in a resting (prepupal) state, kept cool at about 7 °C (45 °F). When crops flower, farmers move bees to a warmer place (around 27 °C (81 °F)). After about 25 days, adults emerge. Then, they are ready for the fields to pollinate!
See also
- List of Megachile species
