Western Honey Bee

The Western Honey Bee:

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Hymenoptera

Family: Apidae

Subfamily: Apinae

Genus: Apis

Species: A. mellifera

Introduction

The western honey bee, Apis mellifera, is one of the many species of honey bees from around the world. It originated in Europe and was brought to the Americas by settlers. Since then, the western honey bee has become an important pollinator of many plants, both wild and domestic. It is also a widely commercially-raised insect, with U.S. commercial apiaries producing 156.5 million pounds of honey in 2015 (U.S. Honey Industry Report, 2016). The honey bee is now wide-spread across the world, with populations existing on every continent except for Antarctica (Mortensen, Ellis, & Schmehl, 2013).

General Biology

Western honey bees are members of the order Hymenoptera, which includes bees, wasps, and ants. They are holometabolous endopterygotes, meaning they undergo full metamorphosis during their life cycle, and their wings develop inside of their body. Like all members of the class Insecta, honey bees have a body divided into three parts - the head, thorax, and abdomen. They also have six legs, with each pair attached to a different section of the thorax. Depending on their caste, the honey bees can look very different from one another.

Worker bees are the non-reproductive females of a hive. They cannot mate, though they can lay unfertilized eggs to produce drones, and will do so in the absence of a queen (Seeley, 1989, p.548). They work to build the colony, defend the hive, feed the larvae, or forage for pollen and nectar, depending on their age. The hind legs of a worker have a corbicula, or pollen basket (Winston, 1987, p.23). These corbicula carry large amounts of pollen for the worker to take back with her to her colony. To help defend the colony, worker bees' ovipositors have been adapted into stingers. When used, the bee's venom sac and stinger are torn from her body, killing her (Mortensen, Ellis, & Schmehl, 2013).

A western honey bee worker with a full corbicula

Compared to workers, drones are larger and generally more plump. They lack corbicula, and because all drones are male, they also lack ovipositors and therefore do not have stingers. Their abdomens are also much more rounded than those of workers. Drones do not forage, build, feed larvae, or defend the hive. Rather, the drones' jobs are to find and mate with a queen from another colony (Mortensen, Ellis, & Schmehl, 2013).

Queen honey bees look similar to workers. However, their abdomen is much longer than that of a worker, making them easy to identify. The queen is the only reproductive female in the hive, except in some circumstances where workers will lay unfertilized eggs. It is her job to lay eggs to provide new workers and drones for the colony. Because she does not forage, the queen, like the drone, lacks corbicula.

Comparison between a worker, a queen, and drone

Eusociality and Reproduction

The western honey bee is a eusocial insect. Eusociality is defined as "[a social group] exhibiting overlapping adult generations, cooperative brood care, and reproductive altruism." (Costa & Fitzgerald, 2005, p.559). Eusocial insects also have reproductive division of labor, as seen in the three castes of the honey bee hive. Because of their high level of sociality, eusocial insects are often referred to as a superorganism (Seeley, 1989, p.548). In honey bees, this superorganism is known as the hive, and usually consists of around 80,000 mature individuals at any one time, as well as up to 30,000 larvae and around 5,000 eggs. The majority of the adults will be non-reproductive workers (Adjare, 1990).

A queen (marked with white paint) surrounded by her workers

The first step of reproduction in honey bees is a process called swarming. After the rest of their colony leaves to find a new home, newly emerged queens will fight each other to the death. Once only one queen remains, she leaves the hive to find mates. In these first few weeks of her adult life, she will mate with around 15 drones and store their sperm in her spermatheca. She will not mate again after this time (Mortensen, Ellis, & Schmehl, 2013).

Once her mating is complete, the queen will begin to lay eggs. Because honey bees exhibit a type of reproduction called haplodiploidy, all eggs that the queen lays that are fertilized will be female, and all unfertilized eggs will be male. To begin with, the queen will lay only fertilized eggs, and she must care for the larvae herself until there are enough worker bees to begin taking care of younger broods. As the queen's sperm supply begins to diminish, she will start to lay unfertilized eggs, which will eventually develop into drones (Adjare, 1990).

The castes of female larvae are determined by their diet. Though all honey bee larvae are fed a worker secretion known as "royal jelly" for the first three days of development, larvae destined to become queens will continue to receive this royal jelly as their food source for the remainder of their time before pupating (Kucharski, Maleszka, Foret, & Maleszka, 2008). Larvae that will become new workers or drones are fed a mix of pollen and honey (Adjare, 1990).

Communication Through Dance Language

One of the most fascinating aspects of honey bee eusociality is the development of a complex dance language, touted by Dr. Gene Robinson of the University of Illinois Urbana-Champaign to be "'one of the seven wonders of the animal behavior world'" (Yates). This language allows forager bees to tell others about a particularly good food source in order to recruit more foragers to gather from it. The dance language was first described by Karl von Frisch. This interpretation of how bees locate food sources was not immediately accepted and was met by considerable resistance in the scientific community, but is now widely considered to be the best explanation for bee foraging recruitment.

There are two kinds of dances exhibited by honey bees, the round dance and the waggle dance, and each gives different amounts of information about the food source the dancer has found. In each dance, the dancer gathers an audience of recruits, and begins to dance. A round dance, which displays a simple looping pattern, tells the audience bees that there is a food source nearby to the hive. After the bee has finished dancing, it will distribute some of the food it has collected to the recruits, which lets them know what the food source smells like. The round dance does not give directional information about the food source, but because the source is nearby, the recruited bees are usually able to find the source fairly quickly (Frisch, 1974).

The paths for a round dance vs. a waggle dance

The waggle dance is more complicated than the round dance and is performed once the food source is at least 50m from the hive. For this dance, the bee will loop in a figure-8 style pattern. At the point where the two loops of the 8 meet, the bee will do a "waggle run" for a specific distance, wiggling her abdomen as she moves across the comb. This waggle run provides several points of information. The length of the waggle run indicates the distance the food source is from the hive. The further the dancer moves while waggling, the further away the food source is. The duration and vigor of the dance indicates the quality of the food source - a higher quality food source will result in vigorous waggling for a longer period of time. Finally, the angle of the waggle run relative to the top of the hive indicates the direction of the food source relative to the sun. For example, if the waggle run is 20° to the right of the exact top of the hive, then the food source will be found 20° to the right of the sun. Like with the round dance, after the dancer is finished with the dance, she will distribute samples of the food she has collected to the recruits (Frisch, 1974).

A forager performs a waggle dance to recruits.

Citations

Adjare, S. (1990). Beekeeping in Africa. Rome: Food and Agriculture Organization of the United Nations.

Costa, J., & Fitzgerald, T. (2005). Social terminology revisited: Where are we ten years later? Annales Zoologici Fennici, 42(6), 559-564. Retrieved from

http://www.jstor.org/stable/23736169

Frisch, K. V. (1974). Decoding the Language of the Bee. Science, 185(4152), 663-668. doi:10.1126/science.185.4152.663

Kucharski, R., Maleszka, J., Foret, S., & Maleszka, R. (2008). Nutritional Control of Reproductive Status in Honeybees via DNA Methylation. Science, 319(5871), 1827-1830. doi:10.1126/science.1153069

Mortensen, A. N., Ellis, J., & Schmehl, D. R. (2013, August). European honey bee - Apis mellifera. Retrieved December 01, 2016, from

http://entnemdept.ufl.edu/creatures/MISC/BEES/euro_honey_bee.htm

Seeley, T. D. (1989, November/December). The Honey Bee Colony as a Superorganism. American Scientist, 77(6), 546-553.

U.S. Honey Industry Report – 2015 | Bee Culture. (2016). Retrieved December 01, 2016, from http://www.beeculture.com/u-s-honey-industry-report-2015-2/

Winston, M. L. (1987). The biology of the honey bee. Cambridge, MA: Harvard University Press.

Yates, D. (n.d.). Honey bees on cocaine dance more, a finding that sheds light on bee language. Retrieved December 02, 2016, from

https://news.illinois.edu/blog/view/6367/206084