Why Do Bees Buzz?: Fascinating Answers to Questions about Bees

6. Bees at Work

SIX Bees at Work Question 1: Why do bees pollinate flowers? Answer: Bees really don’t intend to pollinate flowers, although pollination benefits them because it creates seeds that will make more flowers that will provide them with a continuing nectar flow in the future. Pollen transfer is passive; unless the bee is deliberately collecting pollen to take to the nest, the pollen a bee carries from one flower to another has been deposited by the plant on her back or in another place where she was unable to remove it when she instinctively groomed herself to eliminate dust and debris. As bees go from flower to flower collecting nectar, some of the collected pollen is inadvertently deposited on the stigma of a flower of the same species, resulting in cross-pollination. At certain times when there is a large amount of brood in the colony, honey bees’ primary goal is to actively collect pollen for larval food, storing the pollen on their hind legs on dense hairs referred to as a pollen basket (see this chapter, question 8: Do bees ever stop collecting nectar?). These hairs surround a groove, on the external hind tibia, that creates an elongated cup-like surface where the pollen sits. Bees are able to move some of the passively collected pollen into the pollen baskets, and once the pollen is packed into the transport structures, it is no longer available for pollination and is carried back to the nest. R5192.indb 97 R5192.indb 97 11/30/09 3:02:42 PM 11/30/09 3:02:42 PM 98 WHY DO BEES BUZZ? Lawrence Harder and James Thomson describe flowers that have a dispensing schedule, requiring bees to visit more frequently because the flower’s structure allows only a limited amount of pollen to be obtained in each visit. This increases the likelihood of passive transfer of at least some pollen instead of larger amounts being actively removed to provide larval food or lost to in-flight grooming. Question 2: Which crops are pollinated by bees? Answer: More than one hundred crop species in the United States rely to some degree on bee pollination, and these crops constitute approximately one-third of the American diet, inFig . 19. A worker honey bee showing her specialized leg anatomy for carrying pollen. The arrow points to the corbiculum, or pollen basket. (Drawing by Julie L. Dlugos.) R5192.indb 98 R5192.indb 98 11/30/09 3:02:43 PM 11/30/09 3:02:43 PM Pollination Pollination is the process by which male and female chromosome-carrying cells (gametes) reach each other and fuse (fertilization), enabling a plant to bear fruit and reproduce . The vast majority of all plants are pollinated by living organisms, a process called biotic pollination. Entomophily is pollination by an insect. In addition to bees, moths, butterflies , wasps, ants, beetles, and flies are also insect pollinators . Pollination specifically by bees is called melittophily, although it is hardly a commonly used term. Honey bees and, to a lesser extent, other species of bees accomplish the majority of biotic pollination. Approximately three quarters of the over 250,000 species of flowering plants in the United States rely on mobile animal partners for pollination. Because most bees carry an electrostatic charge that attracts lightweight particles, when they collect nectar from a flower their hairs rub against the plant’s anthers and inadvertently collect the fine, dust-like grains of pollen containing the male gametes. When a foraging bee flies from flower to flower, some of the pollen grains that have been deposited on the bee will be brushed off and deposited onto the receptive female portion (the stigma) of a plant of the same species, usually resulting in fertilization. Sometimes, the goal of the bees is to collect pollen, and some species even moisten their pollen loads with nectar or oil to make it easier to transport (see this chapter, question 7: Do bees ever stop collecting nectar?). The fact that pollen transfer occurs is strictly inadvertent. Some plants only offer nectar and pollen at specific times of the day, and many species of bees learn to adapt their foraging to the availability of their local flowers. Bees have a good sense of time, which makes it possible for them to synchronize their foraging with the plants’ cycle. Because most bees tend to exhibit “floral constancy,” which means that they show a...