Euglossa imperialis is a bee species in the family Apidae. It is considered to be one of the most important pollinators to many Neotropical orchid species in mainland tropical America. It is also one of the most common non-parasitic euglossine species in lowland Panama.Ackerman, James D., et al. "Food-foraging behavior of male Euglossini (Hymenoptera: Apidae): vagabonds or trapliners?." Biotropica (1982): 241-248. E. imperialis, unlike many other bee species, is not a social bee in the sense that there is no apparent morphological or physiological division within the species to distinguish individual bees to be part of a worker or reproductive caste.Roberts, R. B., and Calaway H. Dodson. "Nesting biology of two communal bees, Euglossa imperialis and Euglossa ignita (Hymenoptera: Apidae), including description of larvae." Annals of the Entomological Society of America 60.5 (1967): 1007-1014.
Taxonomy and phylogenetics Euglossa imperialis is a bee species of the Euglossini tribe and Apidae family. The Euglossini are better known as "orchid bees," as they are known to interact almost exclusively with flowering orchid species as pollinators, and are known to search for nectar and chemical fragrances as well. The Euglossini tribe consists of approximately 240 species grouped into five genera—Euglossa, Eufriesea, Eulaema, Exaerete, and Aglae— all of which are spread from northern Mexico to northern Argentina. These euglossine bees comprise up to around 25% of local bee communities in lowland wet forests in this region.Ramírez, Santiago R et al. “Seasonal Cycles, Phylogenetic Assembly, and Functional Diversity of Orchid Bee Communities.” Ecology and Evolution 5.9 (2015): 1896–1907. PMC. Web. 16 Oct. 2015. The Euglossini tribe is also part of the larger Apinae sub-family, which contains many of the known advanced social bees, such as the honey bees, stingless bees, and bumblebees; however, bees of the Euglossini tribe are non-social in nature, meaning that they have not developed a colonial structure with Queen-drone interactions.Roubik, David W., L. A. Weight, and M. A. Bonilla. "Population genetics, diploid males, and limits to social evolution of euglossine bees." Evolution (1996): 931-935.
Phylogenetic community assembly Temporal variation in the structure of euglossine bee communities reveal the relative contributions of varying ecological processes to the shaping of insect communities which include resource competition and habitat filtering. Specifically, phylogenetic diversity changes across latitudinal gradients, in which the more seasonal climates have decreased phylogenetic diversity. It has therefore been theorized that the same ecological processes that drive phylogenetic diversity geographically, also shape communities at the temporal level within a given community.
Description and identification
Euglossa imperialis can be identified from other bees by its relatively large size and relatively sparse hairs, which expose their brightly metallic color.Kimsey, Lynn Siri. "The behaviour of male orchid bees (Apidae, Hymenoptera, Insecta) and the question of leks." Animal Behaviour 28.4 (1980): 996-1004. Males have conspicuous white marks around the mouth, whereas similar markings are diminutive in females. Males also have a broad hind tibia, rhomboid or triangular in shape and rounded distally, used as a storage organ for aromatic materials. Male forelegs have five tarsal segments, which have dense tufts of hairs (or ‘brushes’) on the ventral surface, that are useful for picking up oily liquids by capillarity. An elongated pit covered by long hairs (a ‘scar’) can also be seen on the outer rear surface of the tibia, which shows two lobes, each of which has an opening into the tibial organ. The wall of the tibial organ is extremely wrinkled, on which the inner surface has many large branched hairs. Males also display a characteristic pattern of short, dense hairs on the outer surface of the mid tibia, with one or two small hairy patches within a much larger patch. All E. imperialis are known to have relatively long tongues in comparison to other bee species. They also have two widely separated tufts of hair without any obvious tubes or slits on the second (metasomal) sternum.Dressler, Robert L. "Biology of the orchid bees (Euglossini)." Annual Review of Ecology and Systematics (1982): 373-394.
Distribution and habitat Limited to mainland Tropical America, E. imperialis range from northern Mexico to Paraguay and Argentina.
Male territories occur in light gaps in the forest, including treefalls and trails, and are almost nonexistent in areas of uninterrupted forest. Approximately half of these territories are solitary, of which males tend to be attracted to treefalls which have more potential territory sites. Each territory usually consists of a perch on the trunk of a tree about 0.5 to 1.5 m above the ground, on which the male is displayed, and a route which the male "patrols" to and from the perch. Perches are normally located on tree trunks located on the edge of treefalls. Patrol routes normally extend out into the whole open treefall space. However, it has been noted that territories do not contain flowering plants, sources from which to collect aromatic material (such as tree wounds), nest sites, or nest-building materials. Males also had a preference for use straight, smooth-barked trees about 5 to 10 cm in diameter, with an unobstructed view from the perch site. Studies have also shown that perches for E. imperialis were almost always in the shade receiving between 27.8 and 92.9 lux on sunny days and 14.8 to 46.4 lux on overcast days.
Nest Euglossa imperialis construct their nests with cells clumped in a single cluster, like bumble bee (Bombus) nests, such that it forms a globular structure rather than a comb structure. The nest chamber is approximately spherical in shape with a diameter of 13 cm. The walls are lined with a dark resinous substance thick on the floor and thin at the ceiling. The oldest cells form the bottom layer of the nest, with new cells added on top of each layer. The larvae typically occupy the older cells with eggs in the newer cells. The inner walls of the cells are smooth, whereas the exterior is rough.
Since E. imperialis is not a social bee and lacks a worker cast, the nest is constructed communally. A nest for E. imperialis, is thus the product of a combined effort of many generations of "selfish" individual behavior, indicating that rather than having a Queen dictate the construction and maintenance of the nest, each individual bee contributes to the well-being of a communal nest because it benefits each individual bee's chance of survival to propagate its genes to future generations of progeny.Dawkins, Richard. The Selfish Gene. Oxford: Oxford University Press, 1989. Print.
Life cycle Euglossa imperialis, like many other insect species, undergoes biological change throughout its lifetime via Holometabolism, the four stages of complete metamorphosis:
Eggs Duration of approximately 3 days in cell, eggs of E. imperialis are curved in shape and approximately 5mm long and 1mm in diameter positioned with only its anterior and posterior ends resting on the surface of the provisions.
Larvae Duration of approximately 25 days in cell, mature larvae are ivory-colored and robust with intersegmental lines clearly defined laterally, dorsally, and ventrally.
Pupa Duration of approximately 35 days in cell, including ‘Pre-Pupa’ stage.
Adult Males have been observed to live about six weeks to three months, whereas females have been observed to live about three to six months.
Colony cycle Since E. imperialis is a euglossine species, they are a non-social bee, and therefore lack the formation of colonies. Studies have shown that significant barriers to establish stable perennial colonies arise from two main factors: high diploid male production and genetic polymorphism. There could be no supply of truly altruistic workers (or drones), since the supply would be inconsistent, with up to 50% of the intended diploid females actually being males. Therefore, with no drone class, colonies would not be able to adequately form. Another reason why there is such a high diploid male population is because diploid male larva live within thick, closed off resinous cells which are not readily eliminated by the females. Diploid males are therefore seen as a ‘waste’ in energy and resources, and have no adaptive value to other bees.
For the second main factor, genetic polymorphism, it is theorized that Euglossini bees have not reached a point where the threshold of genetic homogeneity permitting colony fitness has crossed the expected individual fitness. Therefore, euglossine genetic polymorphism levels appear to be higher than those of ordinary solitary bees, and much higher than social bees, since low polymorphism levels is seen as a foundation for advanced social evolution.
Diet
Euglossa imperialis typically feed on nectar from flowering plants, particularly of the orchid species. Studies have shown that the nectar intake rate for E. imperialis is determined primarily by nectar viscosity rather than nectar sweetness, as measured by sucrose concentrations.Borrell, Brendan J. "Mechanics of nectar feeding in the orchid bee Euglossa imperialis: pressure, viscosity and flow." Journal of Experimental Biology209.24 (2006): 4901-4907. E. imperialis also visits a wide variety of deep flowering plants, unreachable to most other bee species, such as Bignoniaceae, Costaceae, and Marantaceae, as well as understorey herbs such as Costus laevis and Costus allenii, which are entirely dependent on female E. imperialis for pollination and cross-fertilization.Borrell, Brendan J. "Suction feeding in orchid bees (Apidae: Euglossini)." Proceedings of the Royal Society of London B: Biological Sciences 271.Suppl 4 (2004): S164-S166. Male euglossines have also been observed to collect chemical fragrances from floral sources—such as Orchidaceae, Solanaceae, Bignoniaceae, and Euphorbiaceae—as well as non-floral sources, including decaying wood, rotting fruit, animal feces, and tree wounds.Eltz, T., et al. "Fragrance collection, storage, and accumulation by individual male orchid bees." Journal of Chemical Ecology 25.1 (1999): 157-176.
Behavior Food foraging Euglossa imperialis are relatively site-constant when it comes to foraging, meaning that they regularly return to the same areas to forage for nectar, reminiscent of traplines. These are specific foraging routes individual bees utilize to visit the same flowering individuals in a daily regular sequence. These traplines reduce the time bees have to spend searching for food each day; each bee has a set circuit and begins foraging from the same plant on consecutive days. E. imperialis forage efficiently in this way by flying rapidly from one precise flowering plant to the next in its daily sequence, even ignoring newly blooming plants adjacent, but outside of, its regular route. Severe shortages of food may also cause males to migrate or change their foraging behavior to become transient and vagabond, in which males will fly longer distances to find food. This behavior can also be expected to change with the changing seasons, as certain plants flower in different seasons.
Nectar feeding behavior