There are over 20,000 species of bees in the world, and they display an incredible diversity in size, color, behavior, and morphology. Most bees are easily distinguished from other flying insects by their furry bodies and their ability to sting. However, there is one group of bees that possesses a unique method of flight similar to their unrelated lookalikes, the hummingbirds. These are the long-horned bees of the genus Melissodes, commonly known as hummingbird bees or horned bees.
Hummingbird bees are mediums-sized, slender bees that are most notable for their exceptionally long antennae which may exceed their own body length. Their wings beat at an astonishingly rapid rate, allowing them to hover in front of flowers as they collect nectar and pollen. This specialized form of flight and flower foraging mimics that of hummingbirds, despite the two groups being taxonomically distant. There are about 150 documented species of Melissodes native to the Americas, but the common name “hummingbird bee” generally refers to Melissodes agilis and Melissodes desponsa in North America. Here is a more in-depth look at the biology and behavior of these fascinating insects.
Taxonomy and Physical Description
Hummingbird bees belong to the family Apidae, which contains all bees that produce and store honey, such as honey bees, bumble bees, stingless bees, and orchid bees. They are placed in the tribe Eucerini along with other long-horned bees. There are 29 genera within Eucerini, the largest of which is Melissodes with over 100 species.
As their name implies, hummingbird bees are characterized by exceptionally long antennae which may exceed the length of the bee’s body in some species. For example, the antennae of male Melissodes desponsa can reach up to 1.5 times the body length. The antennae are covered in sensory organs which allow the bee to detect scents and chemicals. The elongated antennae are thought to help with locating flowers from a distance.
In addition to long antennae, hummingbird bees have slender bodies about 12-15 mm long. They are black or brown in color often with yellow or white markings. The abdomen is adapted to carry loads of pollen back to the nest with long whitish or yellowish scopal hairs. Legs are slender with modified hairs for collecting pollen. As in all bees, females carry a stinger for defense. Males do not have stingers.
Key Traits:
- Long antennae exceeding body length
- Slender, medium-sized body 12-15 mm long
- Black, brown, yellow, or white coloring
- Abdomen with scopal hairs for carrying pollen
- Females have a stinger, males do not
Flight and Feeding
The most remarkable feature of hummingbird bees is their flight, which allows them to hover and replicate the characteristic feeding behaviors of hummingbirds. Their wings beat at rates up to 130 times per second, making an audible humming noise similar to hummingbirds. This rapid wing motion generates the lift necessary for the bees to hover in place.
While hovering, the bee extends its long tongue into the throats of flowers to retrieve nectar. Their tongues can be over 5 mm long. This allows them to feed from flowers with deep corollas, including lilies, penstemons, and sages. The whole process of hovering to feed takes only 1-2 seconds, then the bee darts off to the next flower.
Hummingbird bees get protein from pollen which they actively collect using their legs and body hairs. The scopal hairs on the abdomen help carry loads of pollen back to the nest. Their unique method of feeding makes hummingbird bees important and efficient pollinators for many plants.
Key Traits:
- Wings beat up to 130 times per second
- Able to precisely hover in place
- Feed by extending long tongue into flowers
- Actively collect pollen on body hairs
- Important pollinators of many plant species
Habitat and Range
Hummingbird bees are native to the Americas. Most Melissodes species live in North America, ranging from southern Canada to Mexico and parts of the Caribbean. A few species can be found in South America as well.
They inhabit a variety of warm environments, most commonly open meadows, prairies, deserts, and scrublands. Hummingbird bees frequent many types of flowers in these habitats to obtain nectar and pollen. They seem to prefer plants with long, tubular flowers where they can reach nectar with their elongated tongues. Favorite food plants include monarda, mints, sages, and certain legumes.
The bees are most active during the warmer months when flowers are in bloom. Very little is known about their overwintering behavior, but mated females likely overwinter in underground burrows until spring. The bees reemerge as temperatures warm and flowers become available. Peak activity periods are late summer and fall in most regions.
Key Traits:
- Native to the Americas
- Range across North America down to South America
- Prefer open, warm environments like meadows and scrubland
- Forage on plants with tubular flowers
- Active in warmer months when flowers bloom
- Females overwinter underground
Nesting and Reproduction
Hummingbird bees are solitary ground nesters. Each female constructs her own nest by burrowing into the ground. The nest consists of a main tunnel leading to one or more brood cells. The female gathers pollen and nectar to create a food mass called bee bread for her offspring.
After provisioning the cells with bee bread, the female lays a single egg in each cell and seals it off with soil. She repeats this process several times, making new cells off of the main tunnel. A completed nest may contain around 5 cells on average.
The eggs hatch into larvae which feed on the bee bread. They pupate inside the sealed cells and emerge as adult bees after metamorphosis. Males emerge first and may help the females exit by chewing exit holes. The bees mate near the nest entrance, then females leave to start new nests while males remain near the natal nest. There is typically one generation per year.
Key Traits:
- Solitary nesters
- Tunnels dug in the ground with brood cells
- Cells provisioned with pollen/nectar bee bread
- One egg laid per cell, about 5 cells per nest
- Larvae feed on bee bread then pupate in cells
- Males emerge first and assist females
- One generation per year
Threats and Conservation
Like other native bee species, hummingbird bees face threats from habitat loss, pesticides, climate change, and competition from non-native bees. Their specialized pollination relationship with certain plants also puts them at risk if host plants decline.
Many of the open areas these bees inhabit have been converted to agricultural land or developed for human use. Pesticides and herbicides used in agriculture can poison foraging bees. Even non-lethal doses of chemicals can negatively impact growth, reproduction, and memory in bees.
Climate change causes shifts in flowering plant distributions which can disrupt bee foraging patterns and nutrition. Warmer temperatures may lead to emergences happening out of sync with host plant blooming. Competition from managed species like honeybees and invasive bees may also strain native bee populations.
While not currently threatened overall, localized declines have been observed in some Melissodes species. Providing protected wildflower habitats and limiting pesticide use in key areas would help conserve these essential pollinators. Monitoring and assessment of population trends is needed to detect early signs of decline.
Key Threats:
- Habitat loss
- Pesticide use
- Climate change
- Competition from non-native bees
Conservation Actions:
- Protect wildflower habitats
- Limit pesticide use
- Monitor population trends
- Research impacts of non-native bees
Fun Facts
- The bee’s genus name Melissodes comes from the Greek word for honeybee.
- Their incredibly fast wing beats and sharp sight help them evade would-be predators.
- Hummingbird bees don’t make honey or live in hives like honeybees.
- They get their common name from the loud humming noise created by their beating wings.
- Their long tongue allows them to reach nectar that other bees cannot.
- Hummingbird bees serve as important pollinators for deep-throated flowers adapted to hummingbirds.
- The first specimens were discovered by pioneering entomologist Thomas Say in 1823.
- Males patrol circuits around nest sites to locate emerging females to mate with.
Conclusion
Hummingbird bees such as Melissodes agilis and Melissodes desponsa are truly unique insects that have evolved an incredible hovering ability analogous to hummingbirds. Their distinctive features like elongated antennae and tongues allow them to specialized in collecting nectar from deep tubular flowers. Their important pollination services help maintain healthy ecosystems, but populations may be at risk from factors like habitat loss and pesticides. Conservation efforts focused on protecting wildflower meadows and monitoring bee populations will help ensure the survival of these captivating creatures. While superficially resembling hummingbirds, hummingbird bees have their own amazing behaviors and life histories making them a fascinating part of nature.
