Composition of a bee colony and biological characteristics of individual development

Composition of a bee colony and the role of individuals in production

The efficiency of pollination of entomophilous crops and the overall productivity of an apiary directly depend on the strength of the bee colony. Bees exist only as a social community consisting of one queen, tens of thousands of workers, and hundreds or thousands of drones. No individual is capable of surviving outside the hive. For an agronomist, a strong bee colony is a reliable tool for increasing the yield of orchards, rapeseed, sunflower, and seed crops.

The queen is the only fertile female with developed reproductive organs, responsible exclusively for egg-laying. She has a slender, elongated body, 20–25 mm in length, and weighs up to 200 mg. The viability of the entire colony, its temperament, swarming tendency, and honey productivity depend on her genetic traits, passed on to the offspring together with the drones. The development period of the queen from egg to emergence from the queen cell is 16–17 days, and she becomes sexually mature on the 7th day after emergence.

Worker bees are infertile females that perform all key processes in the hive. The efficiency of the entire colony depends on their numbers. They produce honey, beeswax, pollen, propolis, royal jelly, and bee venom, and also perform the following tasks:

• care for and rearing of brood;
• construction of wax structures;
• guarding the nest;
• collection and processing of nectar and pollen;
• ventilation of the hive.

• Number of worker individuals in a colony — up to 80–100 thousand
• Average weight of a worker bee — 100 mg
• Temperature in the brood zone — 34–35 °C
• Daily egg-laying capacity of the queen in May–June — 1500–2000 eggs
• Development period of a worker bee — 21 days

Drones are males that develop from unfertilized eggs only during the spring-summer period for mating with young queens. Their body length is 15–17 mm, and their weight reaches 200–250 mg. Drones become sexually mature on the 8th–14th day after emerging from the cell. After the end of the honey flow, worker bees destroy the drone brood and drive the males out of the hive. Their overwintering is permitted only in queenless colonies or colonies with an unfertilized queen.

Biological development cycles and seasonal changes in weight

The queen starts egg-laying in spring when the ambient temperature rises to 10 °C and finishes with the autumn cold. The weight of the laid eggs ranges from 0.128 to 0.221 mg. The queen lays the largest eggs at the end of summer, ensuring the rearing of a hardy generation for wintering.

The total weight of worker bees in the hive fluctuates depending on the season. In summer, during the period of maximum honey flow, the wear on the insects increases: due to intense work (especially of the wings), worker bees live only 35–40 days, whereas the overwintering generation is capable of living up to 200 days.

The development of all three types of individuals in a bee colony passes through the egg, larva, and pupa stages. The process of transition from the egg stage to the larva stage lasts three days:

1. On the first day, the laid egg stands vertically in the cell.
2. On the second day, the egg assumes an inclined position.
3. On the third day, the egg lies on the bottom. Nurse bees secrete larval food (jelly), the shell softens and bursts, releasing a white pearlescent larva.

For the first three days, bees feed the larvae with jelly, adding it to the cell on the edge of the drop of food already present. By the end of the third day, bees add bee bread and honey to the jelly. From the third day on, bees feed the larvae a mixture of honey and bee bread. By the end of the sixth day, thanks to good feeding, the weight of the larva increases 1300 times; it stretches along the cell with its head toward the exit and stops taking food. A honeycomb with a large number of worker bee or drone larvae is called a comb with open brood.

By the end of the sixth day, the bees seal the bee larva in the cell with a flat wax cap mixed with flower pollen. Such a cap is porous and freely allows the passage of air necessary for respiration. Drone larvae in cells are covered with a more convex cap. The development of the larva continues in the sealed cell. It straightens out and discharges the remains of undigested food into one of the corners of the cell. After this, the larva spins a cocoon, with which it isolates itself from excrement and the walls of the cell. Then it turns into a pupa.

The pupa is formed on the 11th day after egg-laying; its eyes darken on the 13th day and turn purple on the 16th day. The abdomen darkens on the 18th day, the body becomes brownish on the 20th day, and the young bee emerges on the 21st day. The young bee has a soft chitinous skeleton densely covered with hairs. With age, the chitin gradually hardens, and the hairs are lost. The bee becomes dark and shiny.

Duration of development stages for honey bee colony individuals, days Development stages Queen Worker bee Drone Egg 3 3 3 Larva in open cell 51/2 6 61/2 Larva and pupa in sealed cell 71/2 12 141/2 Total time required for development 16 21 24

The indicated development periods for the queen, worker bee, and drone may vary depending on the temperature in the nest, the strength of the bee colony, and the amount of feed. Under unfavorable conditions, the development periods may be extended by 1–2 days or more.

Bee colony strength – the mass of worker bees in a bee colony – is the most important indicator of the biological and economic state of the colony, measured in kg (appendices, tables 1, 2, 3). First, the number of bee spaces (streets) is determined, which is then converted into mass (it is generally accepted that 1 bee space corresponds to 250 g of bees).

The strength of a bee colony changes throughout the year, reaching its peak in July, when bees are built up for the main nectar flow. This period usually coincides with the flowering of melliferous plants that provide the greatest nectar intake into the hive. Subsequently, the number of bees gradually decreases until the end of the nectar flow, after which the beekeeper must ensure the build-up of bees for the winter. A bee colony should have at least 1.5 kg (6 bee spaces) of bees in the spring, at least 3 kg (12 bee spaces) by July (the main nectar flow), and at least 2 kg (8 bee spaces) by September (before wintering). Weaker colonies are economically unprofitable, as their productivity is low and they require intensive care.

In a strong colony, there are 2.5–3 kg of bees in the spring, 6–7 kg (or more) before the main nectar flow, and at least 2.5 kg of bees before preparing the nests for wintering. Only a strong, healthy colony can produce maximum commercial products (honey, wax, etc.) even in an unfavorable year. Therefore, all the beekeeper's efforts should be aimed at building up the greatest strength of the bee colony by the main nectar flow, which largely depends on the queen's egg-laying capacity.

Preparation for the future season begins in the summer of the current year. If the colony has an old or sick queen, a young, productive mated queen is introduced into the colony, which is then used to build up a large number of young bees for the winter period. They tolerate wintering well and work energetically in the spring, quickly increasing the amount of brood being reared.

After the spring cleansing flight, combs or lower hive bodies not occupied by bees are removed from the nest, the nests are insulated, and feed reserves are replenished (1–1.5 kg of honey and 100–200 g of bee bread per one bee space). As young bees emerge and the colony grows, the nest is timely expanded with combs containing little honey; with the start of nectar collection, wax foundation is provided, and then second and third hive bodies are placed on the hives, which stimulates the development of strong colonies for the main nectar flow.

The body of the bee consists of three well-developed sections: the head, the thorax, and the abdomen, as well as organs of movement (legs and wings). The body of all individuals in a bee colony is covered with a chitinous shell.

The head of the queen and drone is round, while the worker bee's head is triangular; it houses the eyes, antennae, and mouthparts.

The organs of vision consist of two compound eyes and three simple eyes. Compound (faceted) eyes are fixed on the sides of the head and consist of individual units called ommatidia.

Due to the large number of ommatidia, the compound eyes of the drone are highly convex. Using its compound eyes, the bee well distinguishes moving objects and determines the shape of stationary objects during flight.

Simple eyes (ocelli) in the worker bee and queen are arranged in a triangle on the front part of the vertex, and on the forehead in the drone. They have a weak visual perception ability (with their help, the bee distinguishes objects at a close distance – 1-2 cm – and distinguishes the degree of change in light intensity).

Figure 1. External structure of a worker bee: 1 – head; 2 – thorax; 3 – abdomen; 4 – antennae; 5 – simple eyes; 6 – compound eye; 7 – mandible; 8 – proboscis; 9 – glossa (tongue); 10 – maxilla; 11 – forewing; 12 – hindwing; 13 – spiracle; 14 – foreleg; 15 – midleg; 16 – hindleg; 17-19 – thoracic segments; 20 – propodeum (the first abdominal segment that has become part of the thorax); 21-26 – abdominal segments; 27 – stinger.

I II III

Figure 2. Structure of the head:

I – queen bee head; II – drone head; III – worker bee head (1 – simple eyes; 2 – compound eyes; 3 – antennae; 4 – labrum; 5 – mandibles; 6 – proboscis.

Antennae – located on the forehead between the compound eyes, serving as organs of smell and touch. The last eight segments of the antenna contain 14,000–15,000 nerve endings (sensilla).

Mouthparts – the mouthpart of a worker bee belongs to the chewing-lapping type (see appendices, fig. 5). It consists of:

• Chewing system: mandibles (paired upper jaws) and labrum (upper lip).
• Lapping system: maxillae (paired lower jaws) and labium (lower lip).

The maxillae, together with the labium, form an elongated proboscis used by the bee to suck up food.

The thorax (see appendices, fig. 3) of a bee consists of three segments: the prothorax, mesothorax, and metathorax, to which three pairs of legs and two pairs of wings are attached.

The abdomen (see appendices, fig. 4) of a worker bee and a queen consists of 6 clearly distinguishable rings, while the drone abdomen has 7 rings. Morphologically, the first abdominal ring is actually the second (the first has become part of the thoracic region). Each abdominal ring consists of half-rings. The dorsal half-rings are called tergites, and the ventral ones are sternites.

Of the four thoracic tergites, the 2nd is the most developed; having expanded significantly, it forms the major part of the thorax. Wings are attached between the second and third thoracic tergites.

All six abdominal tergites are highly enlarged (covering the edges of the sternites) and form the dorsal and lateral walls of the abdomen. Spiracles (stigmata) are located on the lateral anterior edges of the tergites. The tergites are connected by a flexible pleural membrane and are positioned so that the rear edge of each tergite overlaps the front edge of the previous one. This gives the bee the ability to extend or contract the abdomen, which is necessary for the normal functioning of internal organs.

4 thoracic and 6 abdominal sternites form the lower wall of the thorax and abdomen. Limbs are attached between the sternites and pleurites of the first three thoracic segments. The abdominal sternites are smaller than the tergites, so their edges overlap the ends of the tergites and are connected to them by a flexible pleural membrane, which allows the abdomen to expand in a vertical position. The first and second abdominal sternites are brown and covered with hairs. On the last four sternites of worker bees are located wax glands and wax mirrors.

Worker bees and queens have a stinger at the end of the abdomen (see appendices, fig. 6), whereas drones do not. The stinger is a modified ovipositor and performs a defensive function. It consists of a chitinous unpaired guide (sheath), two movable stylets, a large and a small poison gland, and two palps. The guide is a groove-like structure with two longitudinal ridges on its underside. Two fixed stylets lie against the guide and slide along its rail-like ridges. The stylet ends in barbs, which prevent the bee from pulling the stinger out of mammalian skin; when the bee takes flight, the stinger is torn from its body. When stinging insects with a chitinous exoskeleton, the stinger is not torn off.

Legs (see appendices, fig. 7) – located on the thoracic region and consist of several segments. The legs serve for movement, collecting and transporting flower pollen and propolis (see appendices, figs. 8, 9), as well as cleaning the antennae. The leg consists of five segments: coxa, trochanter, femur, tibia, and tarsus. The jointed tarsus ends with two claws and an arolium (pad) between them. On the front leg, there is a device for cleaning the antennae, and on the middle leg, there is a spur for removing pollen loads.

On the hind legs of worker bees, there are corbiculae (pollen baskets) for storing flower pollen. Queens and drones do not have corbiculae. On the tibia of the middle legs, there are spurs – chitinous outgrowths that the bee uses to detach the pollen load from the corbicula and push it into a cell.

Worker bees have legs adapted for collecting and carrying pollen. The outer surface of the hind leg tibia is slightly indented and devoid of hairs; its chitin is smooth and shiny. This depression, surrounded by a row of long, inward-curving stiff hairs, forms the corbicula, in the center of which is one long, sturdy seta. The bee collects pollen into the corbicula in the form of fairly large pellets – pollen loads.

The first tarsal segment of the bee is significantly enlarged and transformed into a flat, quadrangular plate. The outer side of the first tarsal segment is covered with ordinary hairs, like all other segments, while on the inner side, the first tarsal segment has 9–10 transversely arranged rows of sturdy hairs, forming a brush. Similar brushes are also found on the inner side of the first enlarged tarsal segment of all other legs. Queens and drones do not have these brushes.

The bee brushes pollen off its body using its brushes. The cleaning process occurs as follows:

• With its middle legs, the bee cleans its head and thorax, combing the body from front to back.
• With the brushes of its hind legs, it combs its abdomen from back to front.
• At the wide end of the bee's tibia is a row of sharp, long teeth forming a so-called comb, which serves to scrape pollen off the brushes.

When collecting pollen, the bee tears open the flower anthers with its mandibles, and the pollen grains dust its body. The bee gathers this pollen with the brushes of its front legs; from these, it is cleared by the brushes of the middle legs. In this process, pollen from the left leg falls onto the brush of the right one and vice versa. Next, the brushes of the middle legs are alternately dragged between the brushes of the hind legs (the bee can use its hind legs to scrape pollen from the side walls of the abdomen).

The efficiency of pollination of entomophilous crops directly depends on the bee's working tools — its limbs and wings. The structural features of the legs determine how quickly the insect cleans its sensory organs and exactly how it collects pollen. The design of the wing apparatus directly affects the foraging radius and the speed of nectar delivery to the hive. Understanding these biological mechanisms helps agronomists more accurately calculate the placement of bee colonies on flowering areas.

Working tools: collecting pollen loads and body grooming

The formation of a pollen load is a complex mechanical process that takes place directly during the collection of pollen from flowers. The bee uses brushes and combs on its hind legs to clean its body of pollen grains and form dense pellets. The mass, moistened with nectar, is securely fixed in special depressions on the tibia of the hind pair of limbs.

1. Accumulation of pollen on the brushes of the hind legs while visiting flowers.
2. Scraping pollen with the comb of one leg from the brush of the opposite leg.
3. Moistening the pellet gathered on the comb with nectar and gland secretions to provide stickiness.
4. Shifting the sticky pellet into the corbicula (pollen basket) during the forward and backward movement of the tarsus, with fixation on its bottom bristle.
5. Dropping the finished pollen load into a honeycomb cell using spurs — sharp, durable spikes on the inner side of the tibia of the middle legs.

The brushes of the hind legs also perform another important task — with their help, worker bees extract wax scales from the abdominal pockets between the edges of the sternites. The bee pricks the thin wax with the hairs of the brush and transfers it to the mandibles for comb construction. To clean the sensitive antennae, all three members of the colony have a special apparatus on their front legs. It is designed as a semicircular notch with a durable chitinous comb on the first segment of the tarsus and a movable process of the tibia.

Flight characteristics and wing structure

Bee wings are formed at the pupal stage as outgrowths of the hypodermis of the mesothorax and metathorax. During development, their walls move closer together, forming strong hollow tubes — veins, inside which hemolymph circulates and tracheae and nerves pass. The veins are connected by thin transparent membranes, forming a light and rigid load-bearing frame. Four large longitudinal veins originate from the base of the forewing, connected by short cross-veins. The pattern of the resulting cells is individual for each population of insects, which allows for the determination of their breed.

In flight, the forewing and hindwing pairs work as a single plane thanks to a special coupling apparatus. A groove on the rear edge of the forewing securely fastens with microscopic hooks on the front edge of the hindwing. Strong thoracic muscles ensure a high frequency of wing beats and allow the bee to reach significant speeds even when carrying a load.

• Range in open terrain — 4–5 km or more
• Range in the forest — less than 5 km
• Feed consumption per 1 km — 1 mg