Osmia lignaria

Say, 1837

blue orchard bee, orchard mason bee, BOB

Species Guides

Osmia lignaria lignaria(Eastern Blue Orchard Bee)
Osmia lignaria propinqua(Western Blue Orchard Bee)

A solitary megachilid native to North America, widely managed for pollination of early spring fruit crops including almonds, apples, and cherries. Distinguished by metallic blue coloration, smaller size than honey bees, and unique mud-nesting . Divided into two by the Rocky Mountains: O. l. propinqua (west) and O. l. lignaria (east).

Osmia lignaria by (c) Harley Hosford, some rights reserved (CC BY), uploaded by Harley Hosford. Used under a CC-BY license.

Osmia lignaria propinqua by no rights reserved, uploaded by Steve Wells. Used under a CC0 license.

Pronunciation

How to pronounce Osmia lignaria: /ˈɔz.mi.ə lɪɡˈnɛə.rɪə/

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

Identification

Metallic blue coloration distinguishes from most other native bees. Nests in pre-existing cavities (reeds, holes in wood, keyholes) rather than excavating its own, unlike carpenter bees (Xylocopa). Separated from other Osmia by geographic range and subtle morphological features; O. l. propinqua occurs west of the Rocky Mountains, O. l. lignaria to the east. Olfactory nest recognition —females drag along nest entrance and perform orientation —may aid identification of active nests.

Images

Appearance

Dark metallic blue to blue-black coloration. Smaller than the (Apis mellifera). Body covered in dense hairs for pollen collection. used to deposit chemical marks and mud during nesting.

Habitat

Requires nesting cavities in narrow holes or tubes: natural reeds, hollow stems, borings in wood, cedar shakes, keyholes, or artificial blocks. Needs access to silty or clayey mud of correct moisture content for construction. Found in orchards, gardens, and natural areas with early spring bloom.

Distribution

Native to North America. Range divided by the Rocky Mountains into two : O. l. propinqua (western subspecies) and O. l. lignaria (eastern subspecies). Does not overwinter in Florida or the Gulf Coast due to insufficient cold winter temperatures required for development.

Seasonality

active in early spring when daytime temperatures reach 14°C (57°F). Males emerge first, followed by females days to weeks later depending on warm weather. Females nest for 4–8 weeks, then die. Larvae develop through summer, pupate, and overwinter as adults in cocoons. broken by winter cold; artificial chilling can advance for orchard management.

Diet

feed on nectar; larvae provisioned with pollen-nectar mass by female parent. Visits flowers nearest the nest rather than traveling miles like honey bees. Can visit 75 flowers per foraging trip.

Life Cycle

Complete with solitary nesting. Female constructs linear series of in pre-existing cavity, each separated by mud partition. Lays single per cell on pollen-nectar provision; female eggs placed toward rear (deeper in cavity), male eggs toward front. Larva hatches, consumes provision, spins cocoon, and pupates. overwinters in cocoon, emerges following spring. Sex ratio biased toward males (approximately 3 males: 1–2 females per cavity).

Behavior

Solitary; each female nests independently. Performs in- orientation dance after selecting nest to memorize visual landmarks. Uses olfactory cues—chemical deposits from abdominal dragging—to recognize own nest. Basks in morning sun to reach flight temperature. Docile; stings only if seriously threatened. Stinger modified as guide. Visits nearest flowers rather than distant sources.

Ecological Role

Important of early spring fruit crops, especially almonds, apples, pears, cherries, plums, and blueberries. More efficient pollinator than honey bees for some native crops. Can forage at cooler temperatures than honey bees. Serves as for multiple including kleptoparasitic mites (Chaetodactylus krombeini), cuckoo bees (Stelis montana), sapygid (Sapyga spp.), and chalcidoid wasps.

Human Relevance

Widely managed commercially for orchard pollination, particularly almonds in California. Beekeepers provide artificial nesting materials (reed tubes, paper straws, wood blocks, " condos") and mud sources. Research subject for studying effects, nutritional stress, and solitary bee conservation. Vulnerable to neonicotinoid (imidacloprid), with multi-generational carryover effects documented. Houdini fly (Cacoxenus indagator), a recently introduced kleptoparasite, poses emerging threat to managed .

Similar Taxa

Osmia cornifronsAnother managed for orchard pollination; O. lignaria distinguished by metallic blue coloration and earlier spring activity
Xylocopa spp. (carpenter bees)Both nest in wood; O. lignaria cannot excavate holes and requires pre-existing cavities, while carpenter bees drill their own tunnels
Apis mellifera (honey bee)Both pollinate orchards; O. lignaria is solitary, smaller, metallic blue, nests in cavities with mud partitions, and forages at cooler temperatures

More Details

Pesticide Sensitivity

Research demonstrates that imidacloprid exposure reduces by 20% through direct effects, with additional 20% reduction from carryover effects across . Combined with floral resource scarcity, reproduction declines 57% with male-biased offspring sex ratio.

Nest Management

Propagation success improved by distributing smaller nest boxes throughout orchard rather than central mass-nesting totes with satellite boxes. Equal distribution yields significantly higher return rates.

Silk Production

Larvae spin silk cocoons during fifth instar; silk fibers can be isolated and mechanically tested without preventing cocoon completion, enabling developmental and nutritional research.