Tag Archive for: Bee Genetics

Fertilized vs. Unfertilized Eggs – A Queen Bee’s Gender Reveal Party

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Some of us enjoy celebrating “gender reveal parties” – because the truth is, no one really knows whether a human infant will be male or female until birth (or close to birth in the case of an ultrasound.) Before this technology, however, it was anyone’s guess whether a child would be born as a boy or a girl. During the early stages of pregnancy, the odds of a child developing as one or the other are random, and more or less equal to a coin toss.

Imagine, however, if we humans could determine the sex of our offspring – not when the child was born, nor earlier with an ultrasound scan, but rather at the time of conception! How different and crazy would our world be if there were such a scenario?

Believe it or not, this is the way honeybees determine the sex of their offspring. It’s actually the queen who dictates the sex of her offspring – literally at the time of egg-laying. When a queen lays an egg, she has her own method of laying either a fertilized or unfertilized egg.  As the egg passes through her oviduct, the queen can choose to fertilize the egg by releasing a tiny amount of her stored sperm from her spermatheca. This will fertilize the egg. Conversely, the queen can also choose to not fertilize the egg.

A fertilized egg will become a female honeybee – either a worker bee or a queen bee. An unfertilized egg will develop into a male honeybee – destined to be a drone. In a healthy colony with a healthy queen, most eggs are fertilized. This makes sense since the vast majority of honeybee colonies consist of worker bees, which are always female.

It is astonishing that a single insect, the queen, has this powerful ability to dictate the sex of her offspring right at the time of conception. It is equally astonishing that somehow, she can determine the right quantity of drones and the right seasonality for laying drones at any given time. All of this is within her power, and somehow, she knows exactly what to do.

How much of this decision-making lies within the queen herself versus within the colony is not entirely clear. Is the colony acting in the same way that a baseball catcher acts with a pitcher, calling the type of pitch to throw? Or is the pitcher herself calling the shots in this case? Scientists believe that both are happening, although the queen clearly dictates the final decision.

The colony itself has some influence in determining the number of drones by the way they choose to allocate the honeycomb when building. If the worker bees construct a large amount of drone-sized comb and point the queen towards it then the queen will lay more unfertilized eggs (drones). If the colony does not build any drone-sized honeycomb, then the queen will only lay worker brood. With no appropriately sized comb, what choice does the queen have after all? It is also possible for worker bees to use pheromone signals to help influence the overall frequency of drone laying.

The Five Eyes of the Honeybee

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Did you know that bees have excellent eyesight?  This is because honeybees have five eyes!

This may be surprising, as we know that bees do not rely on any eyesight when they are inside the hive.  The inside of a typical beehive is completely dark. Since vision is impossible inside of a beehive, bees rely on their sense of smell to communicate, using natural chemicals called pheromones. They also navigate by using the feel of their antennae. Outside the hive, however, it’s a completely different story.

When bees are outside, they rely heavily on their sense of sight to find flowers, navigate, and survive – meaning their vision is very important. Luckily, bees have five eyes – including two large compound eyes and three simple eyes, also called ocelli. The compound eyes are located on either side of the bee’s head, while the ocelli are arranged in a triangular pattern on top of the bee’s head.

Compound eyes are what most people imagine when they think of insect eyes. They are made up of thousands of tiny lenses that all work together to make one single image for the bee – though we think they may see things more like a mosaic. Bees’ compound eyes help them see color, movement, and patterns, making their eyes most useful when it comes to visualizing and identifying flowers.

Honeybees need to be accurate at identifying colors to help them find the right flowers to pollinate.  Curiously, the way their compound eyes perceive color is much different than humans. For instance, bees can’t see red, they see more of the ultraviolet (UV) spectrum than humans. Their compound eyes help them see UV iridescence on flower petals, allowing them to easily identify flowers from one another.

The bees’ ocelli, on the other hand, are simpler eyes that only have one lens. They don’t allow bees to see an image but instead enable honeybees to detect the direction and intensity of sunlight. This helps bees follow the sun and navigate during flight. Clearly, bees don’t use maps or GPS technology to find their way back to the hive. Instead, they navigate by using the location of the sun to help them locate flowers, find their hive, and not get lost directionally. This means it’s imperative for bees to have excellent visual sensitivity to the sun, and can gain a fix on the sun’s location in the sky.

Drone honeybees and queen honeybees all have the same five-eye configuration. And while they navigate similarly to worker bees, they use their compound eyes for slightly different purposes. A drone bee’s role outside the hive relies on them looking for a small target – a queen bee to mate, versus flowers to pollinate. This is why their compound eyes are much bigger than that of the worker honeybee. Once drone honeybees arrive at a drone congregation area, they use these enormous compound eyes to help them find suitable virgin queens to mate with.

A queen bee’s eyes are not as big as a drones’ however. Queen honeybees also use their five eyes for navigation, mating, and finding their way home. Once a Wildflower Meadows queen returns home from her mating flight, she uses her compound eyes to find her mating nuc, where she begins her life inside the colony as an egg-laying machine.

Races of Honeybees

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Beekeeping is one of those endeavors where we beekeepers commonly distinguish the different races that make up the world of honeybees.  As human beings, we are quite familiar with the concept of race.  However, it is not often that we consider race as a component of other species.

Race is typically defined as a grouping of similar physical traits and ancestry.  Honeybees, being social creatures from around the globe, have evolved into various races, each of which contain their own distinct physical and ancestral characteristics.  Often, these races show apparent behavioral characteristics as well.  For example, the Italian honeybees are known for their light color and generally docile behavior; whereas Russian honeybees are known for their dark color and their ability to winter in cold climates.

The most familiar races of honeybees, along with their common characteristics are:

– Italian:  known for light color, gentle behavior, rapid buildup and high brood production
– Carniolan:  known for dark color, gentle behavior, and ability to conserve their food stores
– African:  known for their aggressive temperament and high propensity to swarm
– Caucasian:  known for their grey color, low propensity to swarm, and high propolis production
– Russian:  known for their black color, natural mite resistance, and overwintering prowess

Lucky for us beekeepers, honeybees are seemingly unaffected by having multiple races within a hive.  For example, when an Carniolan colony is requeened with an Italian queen bee, the beehive will gradually become lighter and more golden as more of the Italian bees take the place of their Carniolan sisters.  The colony never seems to mind the disparity of the races within it, and temporarily becomes a mixed-race bee society.  The Italian honeybees work right alongside their Carniolan sisters, yellow and black together in harmony, seemingly with no strife or even the slightest concern over racial differences.  It just goes to show that, once again, perhaps humans could learn a thing or two from honeybees and Mother Nature!

half sisters

Half-Sisters

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When we look at a colony of bees, we tend to think of the hive as a family.  It is, in fact, more or less very much like a typical single-parent family, with a mother – the queen bee – and her sons and daughters.  What is unusual about a hive of honeybees, however, is that not all the bees in the hive share the same father.  Some bees don’t even have fathers!  This leads to some unusual relationships between the bees themselves.

The bees that do not have fathers are the drone bees.  They originate from unfertilized eggs, and have only one set of chromosomes, the queen’s.  Drones in a hive are true genetic brothers, each carrying only the queen’s genetics.  Drone bees, however, are not entirely related to their sisters – the worker bees – who in fact do have fathers.

The worker bees originated from fertilized eggs that carry the genetics of both the queen mother and various drone fathers.  This makes many of the worker bees half-sisters to each other.  Because their mother, the queen, mated with upwards of 15 drones, many of the worker bees within a colony have different fathers.  This explains why sometimes worker bees within a hive can look differently from each other.  Many of the worker bees are not sisters, but are actually half-sisters.

Missing from every beehive is any evidence of the fathers of the worker bees.  One will never find the father of a bee actually in the same hive as the daughters.  You might say that the fathers are “deadbeat dads,” but this would not be completely true.  The fathers are actually “hero dads.”  All drones die during mating, so that no honeybee ever gets to know her father and no drone honey bee father ever gets to know his daughters, as they gave up their lives in the very act of mating and furthering the welfare of not only the colony, but the entire species!