HONEYBEES AND POLLINATION
Honeybees are flying insects. In Pakistan as with most of Southeast Asia, the species diversity of honeybees is high and consists of four species i.e. Apisdorsata, Apiscerana, Apisflorea and Apismellifera .First three are local bees while Apismellifera is European honey bee. Two of these i.e. Apisdorsata and Apis florae cannot be domenticated. Apiscerana and Apismellifera can be managed. The best-known bee species is the European honey bee (Apismelifera) which produces more quantity of honey, as compared to the other types. Human management of these species is known as beekeeping or apiculture. Honeybees are known for their role in pollination and for producing honey and beeswax. There are nearly 20,000 known species of bees in seven to nine recognized families though many are un-described and the actual number is probably higher. They are found on every continent except Antarctica, in every habitat on the planet that contains insect-pollinated flowering plants. Bees visit flowers for feeding on nectar and pollen. The nectar for energy and the pollen for protein and other nutrients. Most pollen is used as food for larvae.
There are three castes of honey bees: queens, which produce eggs; drones or males, which mate with new queens and have no stinger; and workers, which are all non-reproducing females. The queen lays eggs singly in cells of the comb. Larvae hatch from eggs in three to four days. They are then fed by worker bees and develop through several stages in the cells. Cells are capped by worker bees when the larva pupates. Queens and drones are larger than workers and so require larger cells to develop. A colony may typically consist of tens of thousands of individuals.
Development from egg to emerging bee varies among queens, workers and drones. Queens emerge from their cells in 16 days, workers in 21 days and drones in 24 days. Only one queen is usually present in a hive. New virgin queens develop in enlarged cells through differential feeding of royal jelly by workers. When the existing queen ages or dies or the colony becomes very large a new queen is raised by the worker bees. The virgin queen takes one or several flights and once she is established starts laying eggs in the hive.
A fertile queen is able to lay fertilized or unfertilized eggs. Each unfertilized egg contains a unique combination of 50% of the queen’s genes and develops into a haploid drone. The fertilized eggs develop into either workers or virgin queens.
The average lifespan of a queen is three to four years; drones usually die upon mating or are expelled from the hive before the winter; and workers may live for a few weeks in the summer and several months in areas with an extended winter.
Bees play an important role in pollinating flowering plants, and are the major type of pollinator in ecosystems that contain flowering plants. Pollination is very important. It leads to the creation of new seeds that grow into new plants. It begins in the flower. Flowering plants have several different parts that are important in pollination. Flowers have male parts called stamens that produce a sticky powder called pollen. Flowers also have a female part called the pistil. The top of the pistil is called the stigma, and is often sticky. Seeds are made at the base of the pistil, in the ovule. To be pollinated, pollen must be moved from a stamen to the stigma. When pollen from a plant’s stamen is transferred to that same plant’s stigma, it is called self-pollination. When pollen from a plant’s stamen is transferred to a different plant’s stigma, it is called cross-pollination. Cross-pollination produces stronger plants. The plants must be of the same species. For example, only pollen from a daisy can pollinate another daisy. Pollen from a rose or an apple tree would not work.
Pollination is necessary for all seed and fruit production by flowering plants. Transfer of pollen among flowers to allow their reproduction is a vital mechanism for maintaining life on earth. People harvest the seeds of some crops for food; examples are oilseed crops, nuts, legumes such as beans and peas, and cereals such as rice and maize. Other crops provide fruit that develops with the seed, for example citrus fruits, mangoes and tomatoes. Seed is required for the production of the next generation of crops and allows plant-breeding programmes to improve varieties.
Qualities of honeybees which make them good pollinators are: body covered with hairs and has structural adaptation for carrying nectar and pollen, bees do not injure the plants, adult and larva feed on nectar and pollen which is available in plenty, considered as superior pollinators, since store pollen and nectar for future use, no diapauses is observed and needs pollen throughout the year, body size and proboscis length is very much suitable for many crops, pollinate wide variety of crops and forage in extreme weather conditions also.
Bees either focus on gathering nectar or on gathering pollen depending on demand, especially in social species. Bees gathering nectar may accomplish pollination, but bees that are deliberately gathering pollen are more efficient pollinators. It is estimated that one third of the human food supply depends on insect pollination, most of which is accomplished by bees, especially the domesticated European honey bee. Contract pollination has overtaken the role of honey production for beekeepers in many countries. Monoculture and the massive decline of many bee species (both wild and domesticated) have increasingly caused honey bee keepers to become migratory so that bees can be concentrated in seasonally varying high-demand areas of pollination.
Most bees are fuzzy and carry an electrostatic charge, which aids in the adherence of pollen. Female bees periodically stop foraging and groom themselves to pack the pollen into the scopa, which is on the legs in most bees, and on the ventral abdomen on others, and modified into specialized pollen baskets on the legs of honey bees and their relatives. Many bees are opportunistic foragers, and will gather pollen from a variety of plants, while others are oligolectic, gathering pollen from only one or a few types of plant. A small number of plants produce nutritious floral oils rather than pollen, which are gathered and used by oligolectic bees. Pollen and nectar are usually combined together to form a pellet of various shapes and stored in a small chamber the “cell”, with the egg deposited on the mass. The cell is typically sealed after the egg is laid, and the adult and larva never interact directly.
Pollination occurs in several ways. People can transfer pollen from one flower to another, but most plants are pollinated without any help from people. Usually plants rely on animals or the wind to pollinate them. When animals such as bees, butterflies, moths, flies, and humming birds pollinate plants, it’s accidental. They are not trying to pollinate the plant. Usually they are at the plant to get food, the sticky pollen or sweet nectar made at the base of the petals. When feeding, the animals accidentally rub against the stamens and get pollen stuck all over themselves. When they move to another flower to feed, some of the pollen can rub off onto this new plant’s stigma. Plants that are pollinated by animals often are brightly colored and have a strong smell to attract the animal pollinato
Dr. Farida Iftikhar