Studies on the nature of the interactions between plants and animals are important to understand the structure and dynamics of ecosystems services, and have helped clarify issues of regeneration and conservation of resources. Mutual adaptation of flowers and insect pollinators especially honeybees and their interdependence are considered to be the result of their intimate co-evolution through geological ages. Many forms of flowers evolved due to selective pressure of pollinators. Flowers have to match with the needs of the pollinators and vice versa in the competition for limited resources. Whether it is for pollination or for food, selective pressure is directed towards increasing the excellence of the match between flower and pollinator (Bawa and Hadley 1990).

As flowers can be regarded as pollination units, their functional structure is closely related to their pollination mechanisms. In the animal pollinated flowers, usually the corolla is variously coloured, with different shapes and fragrances and produce nectar and pollen to attract the pollinators.  The corolla also functions as a landing centre for pollinators, especially the insects. When the flower is ready for pollination the stigma of the female reproductive organ, the gynoecium gets sticky surface to which the pollen brought by the pollinator can stick and germinate to form the pollen tube that carries the male gametes into the ovary to the female gametes paving way for the seed setting.  Honeybees are highly efficient pollinators. In combination with stingless bees they exploit nectar sources rapidly and surplus nectar is accumulated in their hives (Visscher & Seeley, 1982). The members of the family Apidae, including our honey bees, are long tongued with which they can suck nectar from nectaries situated deep in the flower. 

Honey bees depend on plants for varied purposes such as for food in the form of pollen and nectar, and resin or propolis as an adhesive for attachment and repairs of hives. Pollen being the principal source of protein, fats, vitamins and minerals, it is essential for brood rearing and growth in colony strength. Nectar consists of carbohydrates, mainly sucrose, fructose and glucose, and is the raw material of honey (Duangphakdee et al., 2009). The composition and properties of honey varies with floral sources utilized by the bees as well as regional and climatic conditions (Trstenjak et al., 1993; Salinas et al., 1994; Perez- Arquillue et al., 1994). Regardless of the initial concentration of sugar in the nectar, that varies from plant species to species, honeybees must concentrate nectar to at least 82% for larval food storage, by a process of evaporation first on their tongues and later in cells (Winston, 1987).

The bees depend on flowering plants of all life spans such as annuals, biennials and perennials and of habits like herbs, shrubs, trees and climbers. Notable examples of some of the annual plants that the bees forage for pollen and nectar are sunflower (Helianthus annus) and mustard (Brassica juncea). Studies showed yield increase to the tune of 67.7% and 28.08% respectively in mustard, for open pollinated crop and crop enclosed along with honey bees, respectively, compared to control crop enclosed without honey bees (caged without bees) (Harichand and Singh,1995). Nath and Viraktamath (2010) found that A. dorsata constituted 96.14% of the pollinators of sunflower followed by A. florea (3.35%)and A. cerana (0.51%) respectively.  Several biennial crops also depend on bees for pollination. Honeybees were found to be predominant pollinators of cauliflower in Haryana. Among honeybees, Apis dorsata, Apis mellifera, Apis cerana and Apis florea constituted 28.3%, 26.32%, 24.20% and 21.23% respectively (Selvakumar et al., 2003). Perennials or plants that live for several years and producing flowers year after year (For e.g. Mango, Banana, Cashew, wild trees and others) are very important in bee-keeping. To maintain beehive populations throughout the year we need a mixture of crop plants including annuals (eg. sunflower, mustard), biennials (eg. radish, sesame) and perennials (eg. mango, soapnut, neem). Such mixed group of species of different habits and life spans, in combination with selected group of wild plants of the region will help in optimizing honey yields almost throughout the year. 

Bee-flora is the most important factor in bee management as the bee population; its health and survival are related to the abundance of mainly the nectar plants on which the bees forage. Adequate nectar and pollen resources are critical in maintaining honey bee health (Haydak, 1970; Zamarlicki, 1984; Michener, 2007). A deficiency in quantity and quality of pollen and nectar can lead to population decrease of the colony; low colony populations in turn further reduces the number of bees available to collect pollen and nectar (Keller et al., 2005). Moreover, recent work has shown the importance of pollen quality and diversity on the immune response of honey bees (Alaux et al., 2010). Decline of bees and their food plants are reported world wide (Biesmeijer et al. 2006 Steffan-Dewenter et al., 2005; Biesmeijer et al., 2006; Goulson et al., 2008; Freitas et al., 2009). Sustainable beekeeping in India can only be achieved through understanding and conservation of the most resourceful plants for the bees in terms of nectar, pollen and resin. Knowledge on bee-plants that are important to bees in different localities and seasons is still very scarce in India. Therefore we have attempted here documentation of important plant species to enrich the honey production. Our data was collected by primary field survey, interviews with bee farmers as well as from literature surveys applicable to the focal region (Sivaram, 2001; Banakar, 2009; Thomas et. al., 2009; Danaraddi et al., 2009 and Roy et. al., 2011). In Table 7.1 is given a list of nectar/pollen plants suitable for bee farming in Uttara Kannada district. We have also presented a more elaborate list of plants suitable for bee foraging in Karnataka State, based on Sivaram (2001) in the Annexure 2. The genera like Syzygium, Terminalia, Strobilanthes, Holigarna, Sapindus, Vateria, Lagerstroemia, Phyllanthus, Areca, Cocos, Caryota, Crotalaria, Dalbergia, Pongamia, Pterocarpus, Xylia, Strychnos, Careya, and Vitex are some of the very important genera as food sources for honeybees in Uttara Kannada.

Honeybee species have their own preferences for plants as habitats. This host specificity is determined by branching pattern, flowering phenology and provision of holes and crevices in tree trunks (Table 7.2). Apis cerana (cavity nesting bees) require cavities and hollows in big trees for nesting. Apis cerana are considered as photophobic bees and prefer shaded parts for colonization. In our study areas we could observe its nesting sites in trees like Caryota urens, Careya arborea, Terminalia paniculata, Lagerstroemia microcarpa and Vitex altissima. Apis dorsata is a more of a light loving bee and in our study area 21 tree species were associated with its colonies, in addition to the giant rock formations of Yana and some large buildings. Tetrameles nudiflora, a very gigantic soft wooded, deciduous tree is a preferred nesting site for this bee and several large sized hives are often seen on the same tree (Plate 7.1.). Trigona iridepennis, the stingless small bees, a minor source of honey (‘misri’ honey of medicinal value) was associated with seven tree species in our study area. In addition it also occurs in the holes and cracks of old buildings (Refer Chapter 6 for more details on promoting forage plants for honey bees).

Table 7.1: List of important pollen (P)/nectar (N) plant sources recommended for promotion of bee farming (Major sources in the bold), shrub (S), herb (H), climber (C), and tree (T).

Table 7.2: Nesting plants of honeybees (based on Thomas et. al., 2009; Danaraddi et al., 2009 and Roy et. al., 2011; Nair, 2003 and our own observation).

Plate 7.1: Nesting sites of honey bees