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A bee is a bee, right? Aren't they all the same?
Dear bugeyed Bernie,
"You have mentioned that there are over 350 bee species in Vermont. Are they all the same? If not what is a species example of what is unique and interesting about them?
Tobi Bee Inspired.
Dear Tobi Bee Inspired,
First I congratulate you for thinking there might be differences among bee species. Amongst those in Vermont, there are differences in phenology, population status & nativity, body size, mating behavior and other behaviors, sociality (diversity in social organization), nesting, foraging, cell provisioning, egg, and larva development, life cycle, reproduction, parasites (they are host to or parasites themselves), and plant associations.
Let's cover a few of those characteristics by looking at one Vermont bee species, Macropis nuda (data from VCE - credit given below.) This bee species is commonly called the Dark-legged Yellow Loosestrife Bee.
Loosestrife Bees (Genus Macropis) are among the rarest bees in the Northeast. They are unique in collecting oils from our native Loosestrifes (Genus Lysimachia) and are thus dependent on these yellow flowers. There is some evidence that these bees were once more common and widespread than they are today.
All species of the genus Macropis are oligolectic, as females forage [exclusively] for loosestrife plant oil to line their nests and provision to their eggs. Macropis bees are commonly referred to as oil bees, as they are the main pollinators of oil plants such as plants of the genus Lysimachia.
Genus level ID: these bees are unlikely to be found away from blooming loosestrifes (June – August), however, most bees encountered on loosestrifes will not be Macropis. Look for a larger bee (slightly smaller than a honey bee) that is moderately hairy. Females look like they are wearing bell bottoms, while males have yellow marks on their faces.
Macropis nuda was documented in the state before 1960, and subsequently found in 2020 and 2021. Look for Fringed Loosestrife and Spreading Dogbane in wet areas along meandering rivers, which may provide the nesting substrate for these ground-nesting bees. This species cocoons as pupae and hibernates over the winter.
This species is likely the main host for the cleptoparasitic bee, Epeoloides pilosulus.
Both males and females of M. nuda are roughly 7-7.5mm in length.
The head, thorax, and abdomen of M. nuda females are dark black. Females have dense white scopa on their posterior tibiae that are foraging adaptations used for collecting and carrying floral oils and pollen. These scopae are distinct from other bees as they use capillary action to hold floral oils.
Similar to females, the head, thorax, and abdomen of M. nuda males are dark black. Males are differentiated by having much less scopa, or hair, on their posterior tibiae. Males are characterized by yellow markings on their heads, the broad plate on the front of the head being completely yellow.
As it is an oligolectic* bee, it is found only where plants of the species Lysimachia ciliata grow. *Oligolectic: specializing in only one or a few species of plants.
M. nuda females are particular about their nest sites as their nests are in the ground. Females will make their nests in shady areas of drier, sandy-loam textured soil. Nests are typically near the loosestrife flowers from which females collect oil and pollen. Though females are solitary and build their own nests, nests will be found in aggregates due to the criteria of the nest site.
M. nuda is a solitary* bee species. Females make their own nests in the ground, and are univoltine, having only one brood during a mating season as offspring hibernate in the nest until they mature the next season. Males and females spend the winter in cocoons as mature pupae and recommence development in the spring as the temperature increases. Once emerged, young females will either find a new nesting site or commandeer an old nest. *Solitary: A female performs every step of the child-rearing process by herself - nest construction, brood cell provisioning, and egg-laying.
Larvae rapidly develop into pupae within 10 days, feeding on a provision that is a mixture of floral oil and pollen.
A female M. nuda digs a cell and then lines it with oils from Lysimachia flowers. The female then provisions the cell with a mixture of floral oil and pollen. She then lays a single, white-colored egg in the cell before closing it with soil. The larval feeding period lasts approximately 10–14 days, after which they are pupae and begin to spin cocoons.
After the larval feeding period, pupae spin the cocoons which they will hibernate until the next spring. Cocoons completely occupy the cells and strongly adhere to the sides of the cell, but not the closure. There is a small hole near the apex of the cocoon, opening to the soil closure of the cell. This allows the exchange of oxygen and carbon dioxide as the waxy oil coating the cell and the silk of the cocoon does not allow for gas movement. Not only does the cocoon allow safety from the cold of the winter, it may also serve as a barricade to protect against parasites and predators.
Macropis species are protandrous, as male bees emerge from their cocoons 1–2 weeks before females emerge. Because M. nuda males emerge before females, they also reach sexual maturity earlier. Females reach sexual maturity shortly after they emerge when they begin constructing their nests.
Unlike females, male Macropis nuda do not rely on Lysimachia plants. The daily activity of patrolling males begins near nest aggregates and then progresses to nearby flowers where both males and females feed themselves on a variety of nectars. Males only collect nectar, but will travel to Lysimachia plants for mating opportunities where females collect floral oils. Males attempt to mate by directly pouncing on females, regardless of whether the female is carrying pollen or oil. Males are not allowed into a female's nest and rest on flowers while females will sleep in their nests.
Macropis nuda does not have any clear mating rituals. There has been no observed scent marking, and males and females do not produce any kind of sound to attract one another like other solitary bees such as Meganomia. Mating appears to be quick and random, where males patrol Lysimachia plants and pounce on females. Females reject males that pounce for mating by swiftly kicking with their hind legs. If receptive, a pair will hold together and fall from a flower, dislodging in the air or landing on the ground. The act is quick and takes around 1–2 seconds to complete. Copulation has only been observed near the Lysimachia plants, never near nest sites.
M. nuda is parasitized by Epeoloides pilosulus, commonly referred to as a "Macropis cuckoo bee". The common name of this cleptoparasite refers to how this species of bee invades a host nest and lays its eggs in a host cell. Macropis cuckoo bee larvae make cocoons and hibernate similarly to M. nuda. The parasitic bee larvae will consume provisions stored for the M. nuda larva. The parasitic bee is most active during the hottest hours of the day. On warm days, M. nuda females will guard the entrances to their nests, impeding the cuckoo bees' mode of parasitism.
- The data above is reported in the Vermont Center for Eco Studies Vermont Atlas of Life Species Report.
Rare/Endangered; declining in the Northeast. S3 in Vermont (uncommon). US Native. Short tongue. Collects pollen via body rubbing and incidental contact.
Males and females not yet having created nests sleep on flowers.
Though females are solitary and build their own nests, nests will be found in aggregates due to the criteria of the nest site. Duration of continuously occupied nesting aggregations: [up to] 40 years.
More on nesting: Nests are compact and rather shallow, as the deepest cells are only up to 6.5mm below the surface. Entrances of nests are usually concealed by dried leaves, twigs, rocks, or low-growing plants. Burrows are approximately 3.0-3.5mm in diameter and are coated with a waterproof lining created from the floral oils collected by the female. The lining maintains homeostatic humidity conditions for offspring. Cells are also coated with this waterproof lining to keep them dry while offspring are in their cocoons during the winter. Genus Macropis nest in well-drained soil often on sloped banks. The same shallow nests were used for consecutive years by successive generations. - The Solitary Bees: The Solitary Bees. Biology, Evolution, Conservation. Nesting biology and DNA barcode analysis of Ceratina dupla and C. mikmaqi, and comparisons with C. calcarata (Hymenoptera: Apidae: Xylocopinae), "J.L. Vickruck, S.M. Rehan, C.S. Sheffield, M.H. Richards".
More on nest provisioning.
The provisions were mealy-pasty moist throughout. Food is a mixture of oil and pollen [assumed]. Provision was formed into elongate, ovoid loaves which were basically consistent in shape from one cell to the next. However, the entire surface, but particularly the bottom part of each loaf, was remarkably irregular, and the degree of unevenness varied from loaf to loaf. Loaf: 5.0 to 5.5 mm long, 3.4 to 4.0 mm wide.
More on Eggs: All eggs 2.3 to 2.9 mm long and 0.50 to 0.55 mm in maximum diameter were on the anterior top of the pollen-masses. Each was curved, translucent white, and possessed a thin, shiny chorion.
Life Cycle: The entire period of adult activity presumably extended for about a month.
-Biology and Immature Stages of Macropis nuda, Including Comparisons to Related Bees (Apoidea, Melittidae), Jerome G. Rozen, Jr. and Ned Robert Jacobson.
More on mating: We confirm Lieftinck's (1957) supposition that the occasional peculiar postures of female Macropis while foraging for pollen or nectar, with their hind legs held outstretched above their abdomens, is in direct response to a male's copulatory pounce. Not only does this effectively dislodge the male but it can then communicate unwillingness to mate thereafter. [Cane, James H., et al. "Foraging, grooming and mate-seeking behaviors of Macropis nuda (Hymenoptera, Melittidae) and use of Lysimachia ciliata (Primulaceae) oils in larval provisions and cell linings." American Midland Naturalist (1983): 257-264]
Other than the highly polyandrous honey bees (Apis), most female bees are thought to be monandrous, though genetic data with which to support this view are generally lacking. There is support from chemoecological studies of bees for this view. [Though more study is needed]. In the solitary bee Andrena nigroaenea, males are attracted by the cuticular hydrocarbon profile of virgin females, and a change in odor profile following mating is associated with a lack of attraction to mate-seeking males (Schiestl and Ayasse, 2000). In the solitary bee O. rufa, the male himself adds odor to a female with whom he has mated that leads to her loss of receptivity and loss of attraction to other males (reviewed in Ayasse et al., 2001). - Male mating behavior and mating systems of bees: an overview, Robert John Paxton, (2020).
Females will feed themselves with nectar of a variety of flowers, but will only use oil and pollen from Lysimachia ciliata plants for provisioning.
Perhaps, Tobi Bee Inspired, this report gives you an idea of the complexity of any given bee species' life and insight into the areas or characteristics that evolution has provided each species with diversity making each species unique. And then there are even differences in individuals within a species - considerable diversity within and between individuals. The more you observe and learn about bees the more you will be Bee Inspired.
Bugeyed Bernie
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