Last week we visited beautiful daggerwing butterflies gathered on a sandy beach in Costa Rica to “pump” water. This week’s episode begins high in the mountains of Costa Rica along the muddy banks of the Savegre River where members of the bee clan known as stingless bees are busy gathering mud. Usually we think of bees foraging for nectar and pollen rather than water logged soil, but some species of stingless bees put this mud to good use in the fortification of their colony.
With pollen baskets full of mud, this worker will soon return to the colony with her load of construction materials.
Typical nesting sites for stingless bees include tree hollows and crevices in the ground. Often these hollows have rather large openings. To limit access to the colony and facilitate defense, these large openings are narrowed to trumpet-shaped entrances constructed with a sticky substance called propolis, a mixture of wax and other materials. Mud gathered by bees along the river may also be incorporated into the nest entrance as a defensible portico to repel ants and other creatures that would love to raid the colony and plunder the honey, pollen, and baby bees inside. In addition to natural cavities, stingless bees take advantage of human-made structures to build their nests. While visiting a rest camp near the Mayan ruins at Xunatunich in Belize, we discovered several colonies of stingless bees occupying cinder block walls of a building. Small cracks in the mortar provided perfect entryways to the hollow cavities inside the block walls.
One colony in a cinder block wall was comprised of stunningly beautiful delicate bees known locally as Blondies. They went about their business seemingly oblivious to students and a bug geek with a camera. However, a second darkly colored species nearby was not nearly as docile. The nest entrance was guarded by several workers that watched carefully and mounted a surprising attack when humans ventured too close. The assault consisted of dozens of workers flying into faces and hair of the students. They seemed to pay special attention to eyes, noses, and ears. Although they lacked stingers, their annoying bites were very persistent, forcing the intruders to vacate the vicinity of the hive. In his book “The Insect Societies”, E.O. Wilson describes accounts of stingless bees attacking human intruders. Some species eject an irritating liquid that causes a burning sensation to skin. This trick has earned them the local name of cagafogos or “fire defecators” in Brazil. So potent is this defense that it may dissuade very aggressive attackers like army ants from entering nests.
Watch as several bees fan their wings near the entrance of this large colony. Some scientists suggest this behavior may help cool the colony on hot days.
A visit inside the colony would reveal the queen busily filling brood cells with eggs, most of which will become workers. The life of a worker bee is a predestined regimen of tasks that change as the bee ages. For the first several days of life, worker bees are craftsman shaping and forming the basic building materials of the colony, wax and a wax-like material called cerumen. After a week or so and for several weeks thereafter, workers stock cells with food and have the heady assignment of feeding the queen. About this time they also begin to produce wax to build the many structures of the nest. Soon workers enter guard duty at the nest entrance. Shortly thereafter, they take on the assignment of collecting nectar and pollen for the hive.
On a warm sunny day, busy workers return to the colony with food for the young.
Worker bees were common visitors to many kinds of flowering plants in the Central American rainforests. I have captured some species and gently rolled them between two fingers. Don’t ask why, but they emitted a pleasant floral odor before I released them. For centuries, ancient Mayans maintained colonies of stingless bees to produce honey used for sweetening foods and to produce a fermented drink similar to mead. Unfortunately, with the introduction of Africanized bees and domestic honeybees, the number of colonies of stingless bees has declined dramatically and husbandry of stingless bees is becoming a lost art. In addition, fragmentation and loss of natural forests in Central and South America threaten many species of marvelous stingless bees and the tropical plants they evolved to pollinate.
Foraging workers visit beautiful blossoms of many species collecting nectar and pollen.
We thank Lee Hellman and the hearty crew of BSCI 339M: Tropical Biology in Belize and the fearless guides of the Aguila de Osa and Rafiki lodges for providing the inspiration for this Bug of the Week. The fascinating book "The Insect Societies" by E.O. Wilson, and the articles “Behavioural and developmental responses of a stingless bee (Scaptotrigona depilis ) to nest overheating” by Ayrton Vollet-Neto, Cristiano Menezes, and Vera Lucia Imperatriz-Fonseca, and “Maya Beekeeping Tradition Fades” by Stefan Lovgren were used as references for this Bug of the Week.