By Mary Free, Extension Master Gardener

At a mere ¼-inch long, Hylaeus bees do not dominate a flower like fuzzy bumble bees three to six times their size. However, if you have sharp eyes or a zoom camera lens you can appreciate their unique appearance and BEE-havior. Hylaeus are distinguished by yellow or white markings on their faces giving rise to their common names, yellow-faced or masked bees, and very few hairs on their bodies.

Since the female Hylaeus has no external structures to collect pollen–see Bee-havior: Gathering and Transporting Pollen–she carries both nectar and pollen in her crop, a compartment in her stomach. The female in the video below demonstrates how she concentrates the nectar-pollen compound by blowing out and drawing in nectar bubbles, which reduce the water content of the nectar. She regurgitates this compound into the individual nest cells to feed her developing larvae.

Video © 2020 Mary Free

Hylaeus bees belong to the family Colletidae, also known as plasterer or cellophane bees. They possess (arguably) the most primitive of bee mouthparts, including short, brush-like tongues. A Hylaeus female makes her nest in cavities by mixing her saliva with secretions from her abdominal Dufour’s gland (part of her stinging apparatus) to make a waterproof cellophane–like substance that she brushes or “plasters” on the cavity with her tongue. She uses a like mixture to make individual cells for her eggs. To see how she accomplishes this, watch the video, Yellow-faced bee (Hylaeus communis) making its cellophane-like nest.

A male Hylaeus bee on Pycnanthemum muticum (short-toothed mountain-mint) in late June. Photo © 2020 Mary Free.

If you grow some of their favorite nectar flowers like Pycnanthemum muticum (short-toothed mountain-mint), Asclepias incarnata (swamp milkweed), or Eupatorium perfoliatum (common boneset) in your garden, then keep your eyes peeled for these tiny creatures. They may delight and surprise you.

References

• Almeida, E.A.B. Colletidae nesting biology (Hymenoptera: Apoidea). Apidologie. Volume 39, Number 1, 16–29 (2008). https://doi.org/10.1051/apido:2007049
• Cole, E., Yellow-Faced Bee – Hylaeus. Pollinator Partnership. U.S. Forest Service.
• Free, M. Bee-havior: Gathering and Transporting Pollen. Master Gardeners of Northern Virginia. (2013).
• Pilkington, G. Yellow-faced bee (Hylaeus communis) making its cellophane-like nest. (2018).
• Tried and True Native Plant Selections for the Mid-Atlantic. Master Gardeners of Northern Virginia.