Osmia ribifloris is a little black bee with a shiny dark green abdomen, slightly smaller than a honey bee. It is one of about three hundred species in the genus known as the mason bees (Osmia), and its subgenus of about twenty closely related species is found throughout the holarctic. This megachilid bee is a solitary bee native to North America. Instead of forming a hive with a queen, individual females lay up to 36 eggs in hollow tubes in reeds or abandoned boring insect holes during a six week period in the spring between mid-March and mid-May. Females make a linear series of chambers, one for each of their eggs, starting at the far end of the tube, placing a morsel of pollen and nectar down, laying their egg on top, sealing the space with mud or masticated plants, and then repeating the process until they have filled the tube. When the eggs hatch after about a week, the larvae eat the pollen left for them, mature into a pupa and then into an adult, all within their chamber over the course of the summer. They overwinter as dormant adults in their cell (Muller 2013; Anderson 1998; Rust 1986).
Osmia ribifloris bees are docile, do not sting readily and are excellent pollinators since they collect more pollen than nectar. Unlike other closely related mason bees, O. ribifloris have a far less generalist flower visitation strategy, pollinate only a few species of flowers, a trait useful in ensuring that those particular plant species cross-pollinate (Anderson 1998; Muller 2013). O. ribifloris has been developed as a commercial blueberry pollinator, and it is estimated that one female bee contributes to about $25 of blueberry production and pollinates about eight blueberry flowers per minute. Many extension programs and garden centers promote advice and services to help individual gardeners to support and breed Osmia and other solitary bees, especially as honeybee populations have declined precipitously since (Bambara 2002; Anderson 1998; Torchio 1990; Sampson et al. 2004, 2013; vanEngelsdorp et al 2009).
Nest in holes in wood blocks or in abandoned nests of Sceliphron wasps. Cell partitions and caps are made of leaf pulp (Cane et al. 2007).
endemic to a single nation
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (200,000 to >2,500,000 square km (about 80,000 to >1,000,000 square miles)) The more western subspecies, O. r. biedermanni occurs from Oregon and California to Utah and Arizona, with the typical subspecies farther east into central Texas (Sampson et al., 2009). This species is not reported from the Boulder, Colorado area by Kearns and Oliveras (2009a,b), but Scott et al. (2011) report O. r. ribifloris from that and six other counties. The species has been used for crop pollination in Mississippi and Alabama where it is not native.
Catalog Number: USNM 536988
Collection: Smithsonian Institution, National Museum of Natural History, Department of Entomology
Collector(s): W. Porter
Year Collected: 1899
Locality: Romeroville, N.M., New Mexico, United States
- Type: 1900. Ann. Mag. Nat. Hist. Ser.7 5: 410.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Comments: both wild and cultivated species of Rubus are apparently among the preferred flowers, and this is an important pollinator. This is also a very effective pollinator of cultivated blueberries. Mitchell also reports visitation of thistles and Ceanothus.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Life History and Behavior
Comments: Adults March to May in most of the range.
Molecular Biology and Genetics
Statistics of barcoding coverage: Osmia ribifloris
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Reasons: This is moderately widespread and apparently fairly common western bee. It has also been used for commercial pollination in the south-central USA where it is not native.
Intrinsic Vulnerability: Moderately vulnerable to not intrinsically vulnerable.
Environmental Specificity: Moderate to broad.
Comments: Adaptable to agricultural use, readily accepts artificial nest bocks.
Global Short Term Trend: Unknown
Global Long Term Trend: Unknown
Comments: Nothing suggesting any large-scale threats to this species was found. It is apparently rather common in many areas.
Global Protection: Unknown whether any occurrences are appropriately protected and managed
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Osmia ribifloris, one of several species referred to as a blueberry bee, is a megachilid bee native to the coastal mountains of southern California. This solitary bee normally gathers pollen from manzanita, but will pollinate blueberries, and is sometimes used commercially for this purpose.
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Names and Taxonomy
Comments: In subgenus Osmia. A subspecies, O. r. biedermanni is often recognized, e.g. Sampson et al. (2009).
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