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ALL ABOUT SUMMER LEAFCUTTER BEES

Summer Leafcutter Bee on Flower

Summer leafcutter bees are gentle, solitary, gregarious, hole-nesting bees that are great alternative managed bees. They are superior pollinators that carry pollen dry and loose on their abdomens.

  • Summer: leafcutter bees emerge in warm summer weather (75F/24C), build protective cocoons for their young out of leaves, hibernate as larvae, and are superior pollinators of tomatoes, peppers, melons, squash, cucurbits, peas, and other summer vegetables and flowers. 

Summer Leafcutter Bees

Alfalfa Leafcutter Bee (Megachile rotundata)

Naturalized after 1940, alfalfa leafcutter bees saved the American alfalfa industry because they are 15 times better at pollination of alfalfa than honey bees. Alfalfa is a very important high-protein feed for livestock. Leafcutter bees are also good pollinators of milkweed, the host plant of the monarch butterfly, whose population is threatened but not currently protected as an endangered species.

Emergence

SUMMER pollinator that begins to emerge after consistent daily temperatures of 75F/24C. Don’t worry, nighttime temperatures don’t affect the bees’ emergence.

Summer leafcutter bees are special because they are able to produce two broods (and sometimes more!) per season. Some of the eggs develop quickly and emerge as adults in the same season as they were laid, these are called second-generation bees. Second generation bees will emerge if the weather is warm enough for long enough.

The evidence of second-generation bees is large holes in capped ends and leafy debris. Unfortunately, with each generation, the amount of bees nesting will diminish as bees disperse to other nesting sites. You may need to supplement with another order of cocoons every few years.

Pollinates

Generalist pollinator (loves most flower types) of summer flowers and vegetables such as melons, peas, squash, tomatoes, peppers, beans, and sunflowers.

Nest-building Material

Females build a protective leafy cocoon to surround the pollen loaf and egg. They use their mandibles (jaws) to cut circles into leaves and these will not harm the plant. Leafcutter bees prefer leaves similar to those of rose, lilac, hosta, and pea. The capped end is made of intact circles of leaves and alfalfa leafcutter bees do not chew up leaf material.

Cocoons

The protective outer layer of the cocoon is made by the mother bee from leaf bits, leaf juices, and bee saliva. Cocoons are sometimes made of flower petals. Leafcutter cocoons are not waterproof and should not be washed.

Incubation

Development into adult bees is called incubation and requires 3 to 7 weeks of warm weather (70-85F/21-30C) with daytime temperature playing a large role. When you buy leafcutter bee cocoons from Crown Bees, we incubate them for you and they arrive ready to emerge.

Identification

Alfalfa leafcutter bees are black with pale yellow stripes on the abdomen and face. At less than half an inch long they are the smallest of the leafcutter bees.

Identifying Genders

Males: emerging first, males are about a third smaller, and their bodies are rounder and brighter than female bees. They have bright green eyes and a white patch of hair on the top of their head.  

Females: emerging up to two weeks later than males, females are larger, darker, and their bodies are flatter. Their eyes are black and they have large mandibles (jaws) needed to cut leaves. The underside of their abdomen is covered in furry white hair that is perfect for collecting pollen. When peeking into nesting holes their faces have a “V” of light hair. 

Life Cycle of Leafcutter Bees

  1. Early Summer: Adults emerge from cocoons and mate. Males are only actively flying for about two weeks.
  2. Summer: Females gather pollen and nectar, build protective leafy cocoons, and seal up nesting holes with intact leaves. Females actively fly for up to 6 weeks.
  3. Summer: If conditions are right, some bees will incubate and develop into adults right away. These second-generation bees mate and continue to nest.
  4. Late Summer-Fall: Larvae enter hibernation within their protective leafy cocoons.
  5. Winter: Hibernate as larvae.
  6. Spring: Larvae begin incubation to become adult bees.