Biology Reference
In-Depth Information
Figure 3.
Recruitment rate of honeybees in relation to concentration. (From Seeley, 1986.)
Solitary
Anthophora pauperata
avoid the abundant but concentrated (70%)
nectar in old flowers of
Alkanna orientalis
(Boraginaceae) in the Sinai desert
of Egypt (Stone et al., 1999). In other environments with seasonal drought,
honeybees also forage on dilute nectars (Percival, 1974). South African bee-
keepers have traditionally moved their hives north of Pretoria in winter (the
dry season), in order to exploit the strong nectar and pollen flow of
Aloe
greatheadii
var.
davyana
(Asphodelaceae), which has a nectar concentration
of around 20% (H. Human and S.W. Nicolson, in preparation). There are
several examples of introduced honeybees foraging on remarkably dilute
nectars and competing with endemic birds for them: these include the nectars
of
Metrosideros collina
(14-21%) in Hawaii (Carpenter, 1976),
Eucalyptus
incrassata
(7%) in southern Australia (Bond & Brown, 1979), both Myrtaceae,
and
Sideroxylon
(Sapotaceae, 10%) in Mauritius (Hansen et al., 2002).
Regardless of the initial concentration, honeybees must concentrate nec-
tar to at least 82% for larval food storage, by a process of evaporation first
on their tongues and later in cells (Winston, 1987). Carpenter bees and bum-
blebees
have also been observed evaporating nectar by repeated regurgitation
(Corbet & Willmer, 1980; Willmer, 1988; Heinrich, 1993). In the West In-
dies, carpenter bees (
Xylocopa mordax
) collect nectar of 45-50% sugar from
Passiflora
and manipulate it on their tongues to a concentration of about
62% before storing it (Corbet & Willmer, 1980). Foraging on concentrated
