Extrafloral Nectar: Entomological Implications

Abstract

Linnacus created the word “nectary” (nectarium) in 1735 to denote specialized epidermal glands composed of small, thin-walled secretory cells from which nectar is brought to the surface through modified stomata (Fahn 1979). Nectar was defined aptly by Trelease (1879) as “a fluid always sapid, usually sweet, often odorous, which is elaborated in any part of a plant, remaining where formed or making its way to some other part; its raison d'etre being the necessity for the removal of some useless or injurious substance, or for some provision to attract nectar-loving animals to the plant for some definite purpose.” The distinction between floral (nuptial) nectaries and extrafloral (vegetative) nectaries was made by Caspary in 1848 (Fahn 1979). The mutual role of floral nectar in plant pollination and insect nutrition is well known (McGregor 1976). Although extrafloral nectar has been the subject of naturalists' curiosity and hypotheses for more than a century (Bentley 1976), only in recent years have we begun to understand its source, characteristics, functions, and chemical ecology.