Eulaema meriana

Eulaema meriana
Eulaema meriana female on a flower of the Brazil nut tree (Bertholletia excelsa)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Apidae
Subfamily:	Apinae
Tribe:	Euglossini
Genus:	Eulaema
Species:	E. meriana
Binomial name
Eulaema meriana (Olivier, 1789)
Synonyms
Euglossa dimidiata Latreille, 1809 Eulaema dimidiata Lepeletier, 1841

Eulaema meriana is a species of large-bodied bee in the tribe Euglossini, the orchid bees. It 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. It is territorial and has 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.

Description

Eulaema meriana is covered in short dense hairs and resembles a bumblebee in appearance. The head is black and the thorax brownish-black with a large, glossy black scutellum. The abdomen is black with three transverse pale yellowish bands on the anterior half and the posterior third is reddish-brown. The membranous wings are dark at the base and paler at the tips. The legs are black and the tibia of the hind legs are much thickened.^[1] The male has hollows on its hind legs and the female has pollen baskets.

Distribution

Eulaema meriana is native to Panama, Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia and Brazil. It is found in forests in the Amazon basin but is replaced in the Atlantic coastal forest by Eulaema niveofasciata and Eulaema flavescens.^[1]

Ecology

As in other species of orchid bee, both the male and female visit flowers to feed on nectar. Besides this, the male has a mutualistic relationship with one or more species of orchid. To persuade the male to visit its flowers, the orchid produces fragrances of a particular chemical composition attractive to that species of bee while the bee is exactly the right size and shape to pollinate the flower.^[2] Stanhopea orchids are mostly pollinated by large Eulaema bees, Euglossa species often being too small for the purpose. In more primitive species in this genus, the pollinarium, a packet of pollen, adheres to the male bee as it reverses out of the flower having collected the fragrance. In more advanced species, there is a fall-through mechanism in which the bee loses its footing on some oil droplets while collecting the fragrance and the pollinarium adheres to the bee as it slithers out of the flower. Eulaema meriana has been observed pollinating Stanhopea candida, Stanhopea costaricensis and Stanhopea tricornis and visiting Stanhopea florida. It also pollinates Catasetum macrocarpum and Notylia pentachne.^[3]

In a study to identify which insects pollinated the flowers of the Brazil nut tree (Bertholletia excelsa), it was found that the flowers were visited by a number of species of bees of which Eulaema meriana was one, though it only visited the tree early in the day. Both males and females were observed collecting nectar from the base of the lower lip. The study concluded that Eulaema meriana played a part in the pollination of the Brazil nut flowers but that other bee species, Eulaema mocsaryi and Xylocopa frontalis, were of greater importance. Nevertheless, in commercial Brazil nut tree plantations, successful pollination depends on the plantation being surrounded by intact primary forest with its epiphytic orchid population to supply a sufficient number of pollinating bees for the large number of flowers.^[4]

Biology

Males of this species are territorial and operate a lek system.^[5] Each selects a perch on the trunk of a tree at the edge of a temporary clearing in the forest caused by a fallen tree. It chooses a site a few metres off the ground on a tree about 25 cm (10 in) in diameter with smooth, bare bark. Here it stands in a characteristic pose with its head close to the bark, its front and hind legs extended and its middle legs folded underneath its body. Periodically it "buzzes", vibrating its wings while opening and closing them to display the yellow abdominal markings. At intervals it takes off and flies a few metres away from the perch before looping back to land close to its previous spot. The same perches are used by males every day, both in the morning and in the afternoon, but are unoccupied for a period in the middle of the day. In ensuing years, the same spots are used again as long as the clearing in the forest still exists.^[5]

Females have large ranges in which they forage and these may contain a number of different male territories, some solitary and others in loose groups. A female attracted to a territory circles around with the male before landing on the perch tree, often taking off again and then settling several times. When the male is successful in landing on the female's back, the mating process lasts for about five minutes, after which time the female flies off. It is not apparent what part the fragrances collected by the male and stored in the hollow in his hind legs play or how they may facilitate the breeding process.^[5]

After mating, a female usually chooses a cavity as its nesting site. If the entrance is too large, a mud wall may first be built in which a hole about 1.5 cm (0.6 in) in diameter is made. The mud is gathered in small balls by the mandibles, transferred progressively to the fore, mid and hind legs, and deposited in the pollen basket on the hind leg. About six balls make a load, three in each basket and the female flies back to the nest site. Inside the cavity, a pedicel is constructed on which an urn-shaped cell is built. The mud of which it is made hardens as it dries. The outside of the cell is usually covered by a thin layer of faeces brought in by the female and the inside is lined with resin which is drawn up to form a flexible collar at the top. Each brood cell is provisioned with a cream-coloured mass made from a mixture of pollen and nectar, tamped down and filling two thirds of the cell. On about the fourth day after the construction was started, an egg is laid in the cell and the female folds in the collar and caps the cell with mud. The pedicel is extended and further cells are built against the long wall of the first giving a group of neatly arranged cells. The construction and provisioning of the later cells occupies less time.^[6]

References