Hylaeus

Fabricius, 1793

Masked Bees, Yellow-faced Bees

Species Guides

21

Hylaeus is a large, diverse of solitary bees in the Colletidae, commonly known as masked bees or yellow-faced bees. The genus contains over 500 with distribution, reaching peak diversity in subtropical Australia and the Hawaiian Islands. These bees are distinguished by their nearly hairless, -like appearance and unique method of transporting nectar and pollen internally in a crop rather than externally on body hairs. Many species nest in pre-existing cavities such as hollow stems, borings in wood, or abandoned galls.

Hylaeus leptocephalus by (c) Amy Schnebelin, some rights reserved (CC BY), uploaded by Amy Schnebelin. Used under a CC-BY license.Hylaeus modestus by (c) Thilina Hettiarachchi, some rights reserved (CC BY), uploaded by Thilina Hettiarachchi. Used under a CC-BY license.Hylaeus mesillae cressoni by (c) Amy Schnebelin, some rights reserved (CC BY), uploaded by Amy Schnebelin. Used under a CC-BY license.

Pronunciation

How to pronounce Hylaeus: //hɪˈliːəs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Most easily confused with small due to nearly hairless, slender bodies. Distinguished from wasps by: (1) presence of (branched) body hairs visible at 60x magnification or higher—wasps have only simple, unbranched hairs; (2) wing venation patterns; (3) of visiting flowers for nectar and pollen. Distinguished from other bees by lack of scopa (pollen-carrying hairs) on legs or , and by characteristic facial markings. Identification to requires examination of male genitalia and microscopic characters.

Images

Habitat

Occupies diverse from urban gardens to natural woodlands. Requires: (1) flowering plants for nectar and pollen; (2) pre-existing cavities for nesting including hollow stems, pithy twigs, borings in dead wood, rock crevices, or abandoned insect galls; (3) bare soil or minimal ground cover for ground-nesting . Often found in areas with standing dead trees or dense herbaceous vegetation providing suitable nesting substrates.

Distribution

distribution worldwide. Approximately 50 in North America. Peak diversity in subtropical Australia and Hawaiian Islands (60+ species historically, several now critically imperiled or possibly extinct). Present across Europe, Asia, Africa, and the Americas. In North America, documented from Michigan, Colorado, California, and Vermont among other states.

Seasonality

activity generally coincides with flowering period of plants, typically spring through late summer in temperate regions. Specific timing varies by and locality. In Michigan, Hylaeus modestus observed visiting flowers from early June through late August.

Diet

feed on nectar from flowers. Larvae provisioned with mixture of nectar and pollen. Pollen plants include: Daucus carota (Apiaceae), Potentilla and Rubus (Rosaceae), Reseda lutea (Resedaceae), Melilotus albus (Fabaceae), Centaurea scabiosae (Asteraceae), Allium sphaerocephalon (Amaryllidaceae), and Campanula trachelium (Campanulaceae). Some exhibit oligolecty (specialization on few host plants), others polylecty ( foraging).

Life Cycle

Solitary nesting. Female constructs nest in pre-existing cavity, creates 1-8 per nest. Each cell lined with glandular secretion forming organic polymer (natural "plastic") that waterproofs and protects provisions. Female ingests nectar and pollen, stores in crop, then regurgitates into cell to form provision mass. Single laid on provision. Larva consumes provision, pupates within cell. emerge from natal nest. No ; each female reproduces independently.

Behavior

Females transport nectar and pollen internally in crop (ingested and regurgitated) rather than externally on body hairs—a unique among bees. Will nest in artificial boxes, bundles of straws, or drilled wood blocks. Males often aggregate near nesting sites seeking mates. Non-aggressive; females possess stinger but rarely use it. Some show flower constancy, returning to same plant species repeatedly.

Ecological Role

of diverse flowering plants. Analysis of larval indicates significant pollen foraging on Rosaceae and Asteraceae when available. Contribute to pollination in urban gardens, natural , and agricultural settings. Serve as for cleptoparasitic bees (e.g., Melecta) and cuckoo wasps (e.g., Pseudomalus auratus). Provide food for insectivorous birds and other .

Human Relevance

Beneficial in home gardens and urban landscapes. Readily use artificial nesting structures ( blocks, straw bundles), making them amenable to conservation efforts. Some Hawaiian critically endangered due to ants and loss, highlighting conservation importance. Useful for monitoring pollinator diversity in urban .

Similar Taxa

  • Small wasps (various families)Nearly hairless, slender bodies with similar size and coloration. Distinguished by microscopic examination of hair structure (simple vs. ), wing venation, and flower-visiting .
  • Colletes (plasterer bees)Also in Colletidae, nest underground, and line with secretions. Distinguished by fuzzy appearance, larger size, and external pollen transport on scopa.
  • Ceratina (small carpenter bees)Similar size, dark coloration, and cavity-nesting habit. Distinguished by presence of scopa for pollen transport and different facial markings.

Misconceptions

Frequently mistaken for due to hairless appearance, leading to unnecessary fear or destruction. Not aggressive and do not defend nests socially. Some originally described as wasps by early taxonomists. Hawaiian species' endangerment often overlooked due to focus on more conspicuous like honey bees.

More Details

Nesting biology

Unlike most bees, Hylaeus lacks strong jaws or leg spines for excavating, forcing dependence on pre-existing cavities. linings composed of unique organic polymers secreted from abdominal glands—one of few examples of natural plastic production in insects.

Conservation status

Seven Hawaiian considered critically imperiled and possibly extinct, primarily due to on , larvae, and pupae. This represents one of the most severe extinction crises documented.

Taxonomic history

Formerly placed in Prosopis; now Hylaeus. Approximately 900 worldwide, making it one of the largest genera. Ongoing taxonomic revisions continue to clarify species boundaries, particularly in Africa and Asia.

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