Euglossa imperialis

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Euglossa imperialis
Euglossa imperialis.jpg
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Apidae
Genus: Euglossa
Species:
E. imperialis
Binomial name
Euglossa imperialis
(Cockerell, 1922)

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. [1] 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. [2]

Contents

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. [3] 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. [4]

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. [3]

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. [5] 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. [6]

Distribution and habitat

Limited to mainland Tropical America, E. imperialis range from northern Mexico to Paraguay and Argentina. [6]

Male territories occur in light gaps in the forest, including treefalls and trails, and are almost nonexistent in areas of uninterrupted forest. [5] 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. [5] 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. [5]

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. [2]

Since E. imperialis is not a social bee and lacks a worker cast, the nest is constructed communally. [2] 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. [7]

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. [2]

Larvae

Duration of approximately 25 days in cell, mature larvae are ivory-colored and robust with intersegmental lines clearly defined laterally, dorsally, and ventrally. [2]

Pupa

Duration of approximately 35 days in cell, including ‘Pre-Pupa’ stage. [2]

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. [5]

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. [4]

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. [4]

Diet

Orchidaceae Starr 070313-5662 Unknown orchidaceae.jpg
Orchidaceae

Euglossa imperialis typically feed on nectar from flowering plants, particularly of the orchid species. [1] 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. [8] 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. [9] 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. [10]

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. [1]

Nectar feeding behavior

Contrary to most other bee species which have a short proboscis to consume nectar with a lapping motion of their hair-covered tongues, the long-tongued Euglossini bees utilize a purely suction feeding method to ingest nectar from deep flowers, such as flowering orchid plants. However, because of the dilemma the euglossine bees face—in which energy content rises linearly with nectar sugar concentration, whereas viscosity rises exponentially—, E. imperialis collect more dilute nectars, relative to their lapping bee counterparts, with sucrose concentrations between approximately 30 to 40%. During the actual ingestion, the glossa of E. imperialis is generally fully extended and stationary, stretching 6 mm beyond the apical end of the feeding tube formed by the galeae and the labial palps. Therefore, the shift in capillary-based lapping to suction feeding for E. imperialis, although decreasing nectar sugar concentration, maximizes the rate of energy intake for each individual bee. [9]

Fragrance collection

1,4-cineole 1,4-Cineol Structural Formula V2.svg
1,4-cineole

Studies of male E. imperialis show elevated levels of territorial behavior when provided with a fragrant chemical, cineole, which attracts other male bees. [11] In addition, it has been observed that these male bees are likely to periodically abandon their territories to forage for chemicals thought to be important for attracting and mating with females. Males have been observed to actively collect aromatic chemicals, especially those produced by orchid flowers, while storing and modifying them in their hind tibiae for later use. [5] Experiments have evidenced that younger male bees are relatively more active at chemical baits than nectar plants, indicating that many younger male bees have relatively no[ clarification needed ] chemical stores to establish a territory and attract females, and must therefore commit more of their energy to foraging for chemicals. Older male bees were found to be relatively more common at nectar plants, indicating that as these male bees age, there is a decline in reproductive activity. [12] However, when studied over time, male E. imperialis did not detectably decrease their fragrance stores in their hind tibiae over the course of two weeks of captivity, suggesting that continuous passive exposure is highly unlikely. Instead, this strongly supports the theory that an active mechanism is required to allow the male to trigger voluntary fragrance release at specific times, such as courting behavior, or other mating behaviors in which sex pheromones are released. [13]

methyl salicylate Methyl 2-hydroxybenzoate 200.svg
methyl salicylate

Territorial display

Male E. imperialis have been observed to occasionally form aggregations of territories considered to be leks. [5] These aggregations typically occur at sites in which they can collect aromatic materials; however, females almost never approach these aggregations. It is also important to note that although leks are formed, they are only facultative for this species (the more suitable sites, the greater the number of habitable territories). Since these territories are aggregated, females have a large selection of males with whom to potentially mate with in the aggregation. [5] Territorial behavior of male E. imperialis consists of two primary components: displaying on the perch and patrolling its territory. During display, the male ‘stands’ on the perch with its head pointed up, and touching the trunk of the tree with its mandibles closed. Only the fore and hind legs touch the tree trunk, in which the forelegs bend and are held besides the head, whereas the hind-legs are held straight away from the body. During its display, the male would also ‘hop’ on-and-off the tree, about 2 cm from the perch, accompanied by a loud buzzing sound. Shortly after displaying, the male then engages in patrol behavior, flying an irregular elliptical path around its territory. This cycle of displaying and patrolling repeats continuously as long as the male remains in its territory and is undisturbed by intruding males. Male E. imperialis are considered to have two types of territories: ‘primary territories’ and ‘secondary territories’. In primary territories, they are almost always defended by males, and is the site for all male-male confrontations. In secondary territories, they are defended for only 1 to 2 hours a day. Secondary territories often serve as a transitional territory for males attempting to move into primary territories by challenging the resident males. [5] Weather also plays a significant role in territorial defense behavior, such that in heavy rain, males would often abandon their territories for the rest of the day. On dark, overcast days, there is also little to no activity. [5]

Mating behavior

Receptive females are the ones to locate male territories by examining tree-falls or large light gaps within their foraging ranges. Female E. imperialis behavior, when entering a territory, initially resembles that of an intruding male. The female flies up within 5 cm of the resident male and hovers until the male flies out to investigate. The male and female then engage in a tight circular flight path, less than 20 cm apart, until the female lands on the perch of the tree. The female then presses its body close to the tree trunk, with its wings held down. The male then lands on her dorsum to copulate with the female, which lasts a brief 5 seconds. After mating, the female then immediately leaves the territory. It is also important to note that mating only occurs in relatively solitary territories in which no other males are present. It is theorized that female E. imperialis possibly only mate once in their lifetime due to the fact that a very limited number of female foraging ranges actually overlap with any given male territory. [5]

Inter/intra-species conflict behavior

Normally only occurring when a resident male of a primary territory is challenged by an intruding male, intra-species conflict is often fleeting, typically lasting 60 seconds or less. Both males typically engage each other by flying around each other, occasionally bumping, within 0.5 to 1.0 m circles. No actual grappling would occur, and this behavior would continue until one male, typically the intruder, leaves. Male E. imperialis typically ignore members of other species, both bees and animals, in the immediate area of their perch and vicinity of their territories. [5] However, Solenopsis ants have a parasitic relationship with E. imperialis, since they enter some of the cells from below the nest and rob the cell contents. [2]

Nesting behavior

Each nest is occupied by several adult females. When a larva matures in its cell, it lays down a layer of silk threads on the cell walls, then coats it with layers of a smooth and shiny substance, creating a sort of cocoon. The larva then defecates and smears its feces in vertical streaks on the inside of the cocoon to cover the lower half of the inner wall. This behavior is unique in E. imperialis, but the reason for its behavior is still unknown. Males, after emerging from their cells, leave immediately and have been observed to never re-enter the nest. [2]

Flight behavior

Since E. imperialis is an important pollinator to orchid species, they experience excessive loads to carry in their hind tibiae for maneuvers, nectar loading, and mate or prey transport. Thus, aerial agility and mobility is a necessary adaptation that bees of this species must acquire. Studies have shown that the energy E. imperialis bees expend on hovering in normal atmospheric conditions is not representative of their maximum aerodynamic performance capabilities. Bee muscle power output is proportional to the product of contraction frequency, muscle strain, and myofibrillar stress; for E. imperialis, the easiest method of enhancing power output is solely relying on increasing muscle strain by increasing the wing stroke amplitude approximately 40-50%. In short, the total inertial power required can be stored in the elastic elements of the thorax, and then subsequently released to reaccelerate the wings for greater lift. [16]

Human interaction

Euglossa imperialis appear to be a shy species when it comes to human interaction. Multiple experiments done with E. imperialis have all noted that tagging territorial males often ends in failure since they leave the vicinity altogether when people walk within 1.5 to 2.0 m of their territories. [5]

Population decline

Sharp pronounced declines in tropical euglossine bee populations at both the native and human-managed levels, have raised serious concerns over a possible global pollination crisis. Since many tropical plant taxa, especially flowering orchid plants, strongly rely on euglossine bee pollinators for cross-fertilization, declining euglossine bee populations could lead to widespread pollen limitation and low reproductive rates. This decline is most likely attributable to human activity such as habitat disturbance—habitat degradation, pervasive pesticide use, pathogen spillover, forest fragmentation, and climatic alteration. [3]

Related Research Articles

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The tribe Euglossini, in the subfamily Apinae, commonly known as orchid bees or euglossine bees, are the only group of corbiculate bees whose non-parasitic members do not all possess eusocial behavior.

Eastern carpenter bee species of insect

Xylocopa virginica, sometimes referred to as the eastern carpenter bee, extends through the eastern United States and into Canada. They nest in various types of wood and eat pollen and nectar. The eastern carpenter bee is similar to most other bee species in that it does not have a queen; in Xylocopa virginica, females are responsible for reproduction, foraging, and nest construction, though they may sometimes have help from their daughters. Xylocopa virginica is sympatric with Xylocopa micans in the southeastern United States.

Bees and toxic chemicals

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Trap-lining Feeding strategy amongst certain families of birds

In ethology and behavioral ecology, trap-lining or traplining is a feeding strategy in which an individual visits food sources on a regular, repeatable sequence, much as trappers check their lines of traps. Traplining is usually seen in species foraging for floral resources. This involves a specified route in which the individual traverses in the same order repeatedly to check specific plants for flowers that hold nectar, even over long distances. Trap-lining has been described in several taxa, including bees, butterflies, tamarins, bats, rats, and hummingbirds and tropical fruit-eating mammals such as opossums, capuchins and kinkajous. Traplining is used to term the method in which bumblebees and hummingbirds go about collecting nectar, and consequently, pollinating each plant they visit. The term "traplining" was originally coined by Daniel Janzen, although the concept was discussed by Charles Darwin and Nikolaas Tinbergen.

<i>Bombus lapidarius</i> Species of bee

Bombus lapidarius is a species of bumblebee in the subgenus Melanobombus. Commonly known as the red-tailed bumblebee, B. lapidarius can be found throughout much of Central Europe. Known for its distinctive black and red body, this social bee is important in pollination.

<i>Aglae</i> Genus of bees

Aglae is a genus of euglossine bees, with the only described species Aglae caerulea. Like all orchid bees, it is restricted to the Neotropics. They are metallic blue. This species, like the genus Exaerete, is a nest parasite on free-living Euglossini. A. caerulea lays its eggs in the nests of Eulaema nigrita, and possibly other Eulaema species.

<i>Xylocopa sonorina</i> Species of bee

Xylocopa sonorina, the valley carpenter bee or Hawaiian carpenter bee, is a species of carpenter bee found from western Texas to northern California, and the eastern Pacific islands. Females are black while males are golden-brown with green eyes.

<i>Tetragonula carbonaria</i> Species of bee

Tetragonula carbonaria is a stingless bee, endemic to the north-east coast of Australia. Its common name is sugarbag bee. They are also occasionally referred to as bush bees. The bee is known to pollinate orchid species, such as Dendrobium lichenastrum, D. toressae, and D. speciosum. It has been identified as an insect that collects pollen from the cycad Cycas media. They are also known for their small body size, reduced wing venation, and highly developed social structure comparable to honey bees.

<i>Bombus fervidus</i> Species of bee

Bombus fervidus, the golden northern bumble bee or yellow bumblebee, is a species of bumblebee native to North America. It has a yellow-colored abdomen and thorax. Its range includes the North American continent, excluding much of the southern United States, Alaska, and the northern parts of Canada. It is common in cities and farmland, with populations concentrated in the Northeastern part of the United States. It is similar in color and range to the American bumblebee. It has complex behavioral traits, which includes a coordinated nest defense to ward off predators. B. fervidus is an important pollinator, so recent population decline is a particular concern.

<i>Euglossa hyacinthina</i> Species of bee

Euglossa hyacinthina, is a species of the orchid bee tribe Euglossini in the family Apidae. With a tongue that can get up to as long as 4 cm, this orchid bee species is found in Central America. Living in a neotropical climate, E.hyacinthina has adapted to hot and humid weather. The bee has darkly shaded, translucent wings and a metallic, glossy blue skeleton.

<i>Euglossa dilemma</i> Species of bee

Euglossa dilemma, the green orchid bee or dilemma orchid bee, is a species of solitary euglossine bee native to a broad area of Central America, and recently introduced to Florida in the United States. It was first detected in Broward County, Florida in 2003, and initially identified as Euglossa viridissima, but further study revealed that E. viridissima as previously defined consisted of two cryptic species, and the one present in Florida was new to science.

<i>Eulaema meriana</i> Species of bee

Eulaema meriana is a large-bodied bee species in the tribe Euglossini, otherwise known as the orchid bees. The species is a solitary bee and is native to tropical Central and South America. The male collects fragrances from orchid flowers, which it stores in hollows in its hind legs. Orchids can be deceptive by mimicking the form of a female and her sex pheromone, thus luring male bees or wasps. Pollination will take place as the males attempt to mate with the labellum, or the tip petal of the flower. Male E. meriana are territorial and have a particular perch on a tree trunk where it displays to attract a female. After mating, the female builds a nest with urn-shaped cells made with mud, feces, and plant resin, and provisions these with nectar and pollen before laying an egg in each. These bees also have complex foraging and wing buzzing behaviors and are part of a mimicry complex.

Pollination trap

Pollination traps or trap-flowers are plant flower structures that aid the trapping of insects, mainly flies, so as to enhance their effectiveness in pollination. The structures of pollination traps can include deep tubular corollas with downward pointing hairs, slippery surfaces, adhesive liquid, attractants, flower closing and other mechanisms.

<i>Exaerete smaragdina</i> Species of bee

Exaerete smaragdina is a species of kleptoparasitic euglossine bees.

<i>Euglossa cordata</i> Species of bee

Euglossa cordata is a primitively eusocial orchid bee of the American tropics. The species is known for its green body color and ability to fly distances of over 50 km. Males mostly disperse and leave their home nests, while females have been observed to possess philopatric behavior. Because of this, sightings are rare and little is known about the species. However, it has been observed that adults who pollinate certain species of orchids will become intoxicated during the pollination.

<i>Xylocopa sulcatipes</i> Species of bee

Xylocopa sulcatipes is a large Arabian carpenter bee. These multivoltine bees take part in social nesting and cooperative nesting. They are metasocial carpenter bees that nest in thin dead branches. One or more cooperating females build many brood cells. They have been extensively studied in Saudi Arabia and Israel.

<i>Eufriesea surinamensis</i> Species of bee

Eufriesea surinamensis belongs to the tribe of euglossine bees and as such is a species of orchid bee. This should not be mistaken with the species group surinamensis, which includes Ef. surinamensis among other Eufriesea species.

<i>Bombus atratus</i> Species of bee

Bombus atratus is a neotropical bumblebee that is found throughout regions of South America, including Colombia, Ecuador, Brazil, and Argentina. It lives in social colonies that include a founder queen/queens, workers and brood. B. atratus is somewhat unusual because of its potential to oscillate between polygynous and monogynous nesting cycles. Bombus atratus was the first species in the genus Bombus that was discovered to display such polygynous nesting patterns. The polygynous nesting cycles lead to certain specific types of behavior including queen-queen aggression. Nests can also be perennial, which is a characteristic rarely found in other bumblebees. B. atratus can be helpful agriculturally because of their ability to pollinate different species of plants. B. atratus has been found to occupy a range of geographic areas and climates throughout South America. Colonies have the ability to thermoregulate nests and keep them a little bit warmer than the outside environment. Foraging workers use muscle contractions to maintain stable temperatures and coupe with seasonal and daily fluctuations in temperature.

<i>Xylocopa pubescens</i> Species of bee

Xylocopa pubescens is a species of large carpenter bee. Females form nests by excavation with their mandibles, often in dead or soft wood. X. pubescens is commonly found in areas extending from India to Northeast and West Africa. It must reside in these warm climates because it requires a minimum ambient temperature of 18 degrees Celsius in order to forage.

<i>Macropis nuda</i> Species of bee

Macropis nuda is a ground nesting, univoltine bee native to northern parts of North America. Thus, this species cocoons as pupae and hibernates over the winter. The species is unique as it is an oligolectic bee, foraging mainly for floral oils from Primulaceae of the genus Lysimachia.

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