Centridini

oil-collecting bees, oil bees

Genus Guides

Centris(Oil-diggers)

Centridini is a tribe of large apid bees distinguished by specialized adaptations for collecting floral oils, often from plants of the Malpighiaceae. Many possess modified leg structures—either combs of flattened, blunt bristles or velvety pads—for gathering oils, which are used in nest construction and provisioning. The tribe includes ground-nesting and cavity-nesting solitary bees with diverse nesting across the Americas. Members exhibit notable thermal , with some desert species remaining active at high temperatures when other bees are inactive.

Centridini by (c) Francisco Farriols Sarabia, some rights reserved (CC BY), uploaded by Francisco Farriols Sarabia. Used under a CC-BY license.

Centris by (c) Chris Ratzlaff, some rights reserved (CC BY), uploaded by Chris Ratzlaff. Used under a CC-BY license.

Centris by no rights reserved, uploaded by Zygy. Used under a CC0 license.

Pronunciation

How to pronounce Centridini: //sɛnˈtraɪdɪˌnaɪ//

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

Identification

Centridini can be distinguished from other Apidae tribes by several morphological features: a very small pterostigma in the forewing, a densely bushy female scopa, and frequently an elongated first flagellomere of the that exceeds the scape in length. Oil-collecting show specialized leg modifications: combs of closely spaced, flattened, blunt bristles on the margins of the first tarsal segments of the front and middle legs, or velvety pads for oil absorption. These structures are absent or reduced in non-oil-collecting relatives.

Images

Habitat

range from arid and semi-arid environments including American deserts, to tropical and subtropical regions of Central and South America. Specific documented habitats include Caatinga (open shrubby vegetation), Cerrado (semi-deciduous forest), dry semi-deciduous forest, Restingas, and estuarine environments. Nesting substrates vary: some excavate ground nests in flat clay or hard soils, others utilize preexisting cavities such as hollow stems, bamboo canes, or borings in wood.

Distribution

Widespread across the Americas from the southwestern United States and northern Mexico through Central America to South America, including the Caribbean islands. Documented from states including Arizona, and throughout Brazil (Bahia, São Paulo, Maranhão, and others), with records from the Guianas to southern South America. Some such as Centris pallida are predominantly desert-dwelling.

Seasonality

Activity patterns vary by region and . Desert species such as Centris pallida are active during periods when ambient temperatures are high. In Brazilian , nesting activity occurs during wet seasons: October–December in Caatinga, August–November in Cerrado, with peak activity in December and January in southern Brazil. Some species produce multiple annually (three to four), with one generation undergoing .

Diet

Most are polylectic, gathering pollen from multiple plant . Oil-collecting species harvest floral oils primarily from Malpighiaceae, with documented sources including Mcvaughia bahiana and Byrsonima intermedia. Pollen is gathered by buzzing from Solanaceae, Caesalpiniaceae, Malpighiaceae, and Ochnaceae. Nectar sources include Melochia tomentosa (Sterculiaceae) and Memora peregrina (Bignoniaceae). provisions consist of pollen masses, oils, and nectar.

Life Cycle

Solitary nesting with females constructing and provisioning individually. Development includes , larval, and pupal stages within sealed cells. Some exhibit direct development without , as ; others show diapause in one annually. in size is common, with females typically larger than males. In some species, males are produced in outermost cells and females in innermost cells of nest series. Development time is similar between sexes in species where measured.

Behavior

Nesting is diverse: ground-nesting excavate unbranched tunnels 8–26 cm deep with linear series of 1–4 urn-shaped ; cavity-nesting species construct linear cell series in preexisting holes using mixtures of sand and oil. Nest entrances are commonly sealed at night with soil, pebbles, or twigs. Females perform buzzing pollination (sonication) to release pollen. Some species exhibit sleeping , with males and females sharing dormitory sites on vegetation near nesting areas. Males of some species show behavioral and morphological dimorphism (large and small morphs).

Ecological Role

Primary of diverse plant including Solanaceae, Caesalpiniaceae, Malpighiaceae, and Ochnaceae. Specialized oil-collecting relationships with Malpighiaceae represent a notable plant-pollinator mutualism. Serve as for cleptoparasitic bees including Mesoplia , Mesocheira bicolor, and Coelioxys species, and are preyed upon by such as Leucospis species.

Human Relevance

Potential for agricultural and native plant systems. Some are active at high temperatures, providing pollination services when other bees are inactive. colonies and artificial nesting structures can attract centridine bees, though these same structures may also attract . No documented direct negative impacts on humans.

Similar Taxa

AnthophoriniBoth are tribes of large, robust Apidae with solitary nesting habits, but Anthophorini lack oil-collecting adaptations and specialized leg structures for floral oil gathering.
EuceriniSimilar in size and general appearance, but Eucerini are primarily long-horned bees with elongated in males and do not possess the oil-collecting morphological specializations characteristic of Centridini.
XylocopiniLarge carpenter bees that may overlap in size and some , but Xylocopini excavate wood or pith for nesting rather than using soil or preexisting cavities, and lack the oil-collecting leg modifications and tiny pterostigma of Centridini.

More Details

Oil collection and nest construction

Floral oils serve dual functions: as larval food provisions mixed with pollen, and as a binding agent in nest construction. The sand-oil mixture used by cavity-nesting creates durable walls and nest plugs.

Thermal ecology

Centris in American deserts exhibit exceptional heat , remaining active at ambient temperatures that cause most other species to seek shelter. This trait allows exploitation of floral resources during periods of reduced competition.