A queen bee indulges in many strange behaviors, not the least of which is choosing the sex of her offspring. Of course, this surreal proclivity is shared throughout the Hymenoptera, a fact that doesn’t make it any less mysterious.
But even more perplexing than the deciding is the implementing. How does the queen fulfill her desire to lay a fertilized or unfertilized egg? We mere mortals have no idea what that might feel like. Does she squirm one way or another to make it happen? Or does she click her tarsal claws and make a wish? Perhaps, as some have speculated, the queen simply tucks her abdomen into a certain position to get the desired result.1
Since the question of implementation is above my pay grade, I will skip it entirely and describe the first days of a worker bee’s life beginning immediately after the sex decision is made, at the point where the fertilized egg leaves the queen’s body to reside within a sweet-smelling waxen chamber. The queen carefully centers her egg in a brood cell and glues the end to the floor so the entire egg stands as vertical as the Washington Monument.
Honey bee queens use an assortment of pheromones to achieve colony goals, and “egg-marking signal” illustrates her control. As an egg leaves her body, the queen coats it with a compound that lets her workers know that she alone laid that particular egg.2 The coating contains chemical odors that laying workers cannot produce, thus enabling police bees to distinguish between genuine queen-laid eggs and imposter eggs that laying workers sometimes deposit in the brood nest.
Once they are discovered, renegade worker eggs are eaten by the egg police, an act which conserves nutrients within the colony and assures that workers — not drones — develop in worker cells. Furthermore, it assures that any drones that are raised carry the queen’s genetics exclusively. Once her scent-marked egg is placed, the queen wanders off to the next available cell, confident her message is clear.
Many Tiny Eggs
Honey bee eggs are often described as rice-like, but they are much smaller than typical grains of rice, measuring anywhere from 1.2 to 1.8 mm long by 0.4 mm wide, and weighing from 0.12 to 0.22 mg.3 Some of the distribution in size is due to genetic differences among queens, and some is just normal same-queen variation. Compared to bee eggs in general, honey bee eggs are unusually small, a situation made possible by a staff of nurse bees that continually feed the larvae as they grow.
The worker bee egg is soft and covered with a flexible covering called the chorion. The egg contains the original fertilized ovum along with a yolk. Inside the egg, the cells begin to divide and differentiate into various tissue types, including the embryo. As the embryo develops, the egg begins to curve and sag, eventually tipping over and coming to rest on its side. Just before hatching time, the shell layers become more transparent and a tracheal network becomes visible as white lines against a graying background.
The Shell Dissolves
While most insects rupture the outer covering of the egg in order to emerge, honey bees do not. In a process called eclosion, the chorion is dissolved and absorbed by the developing bee, meaning you will never find a pile of egg shells on the floor of a brood cell. Immediately before hatch, fluid oozes from splits along the dorsal midline of the larva and coats the outside of the egg. The fluid begins to dissolve the chorion and, as it disappears, the larval segments become apparent.4 This type of system, where nutrients are preserved and reused whenever possible, is typical of honey bee colonies.
Hatching generally occurs after three days, but embryo development within the egg is temperature dependent, so the actual time until hatch can be anywhere from 48 to 144 hours. During that time, the egg loses about 30% of its initial weight.5
Small Yolks and Progressive Feeding
Because the newly-hatched honey bee larva will be fed continuously and intensively until pupation, it doesn’t need to be very big at hatching time, which means the yolk doesn’t need to provide large quantities of nourishment. This type of feeding regimen is called progressive feeding and is similar to the way we feed our children: constantly.
In comparison to honey bees, most solitary bee larvae are fed only once. The mother bee collects pollen, mixes in a bit of nectar, and shapes it into a ball called a “pollen loaf.” On top of the fresh pollen loaf, she lays an egg and then splits, leaving the offspring to fend for itself. This type of feeding is called mass provisioning. Because the lonely pollen loaf is the only food the larval bee will receive between hatch and pupation, a head start in the form of a large and nutrient-rich yolk is important to survival.
Throughout the bee families, egg size is often inversely proportional to the number of eggs a female bee lays. For example, most female carpenter bees lay very large eggs — some over a half-inch long — but she may only lay ten of these monsters in her lifetime. In comparison, a honey bee queen may lay 2000 eggs per day in peak season.
The Open Larval Stage
The second stage of honey bee development begins as the chorion melts away to expose the white, legless grub known as a larva. The larval stage is the eating stage, the only stage before adulthood where food is taken in from outside its body. In contrast, during the egg and pupal stages, the bee lives on stored nutrients in the yolk and in fat bodies respectively, but nothing new is brought in from the outside.
Eating is what larvae do best. Like stand-alone digestive machines, a larva’s entire body is designed to consume and process vast quantities of food. Their bodies consist of a mouth, salivary glands, a mid- and hind-gut, and an intestine with no exit.5 They have a few other parts, including spiracles for breathing and silk glands for spinning a cocoon, but otherwise they are one-trick ponies that do nothing but munch.
Feeding the Kids
During the first two days of a larva’s life, it eats a rich, two-part diet tendered by the nurse bees. The little white crescent-shaped grubs literally float in an ever-replenished pool of brood food. Most of the meal comprises a clear liquid secreted by the nurse bee’s hypopharyngeal glands. The second component is a milky-looking liquid from the mandibular glands.
Depending on conditions, workers may visit each brood cell from many hundreds to over a thousand times per day. The worker inspects the food supply to see if