Biology Reference
In-Depth Information
for adult
Cotesia glomerata
(Braconidae), and found that this parasitoid can
utilize a wider range of sugars than its host, the butterfly
Pieris brassicae
.
The solitary pollen wasps (Masarinae) are a small group of sphecid wasps
that resemble bees in that they provision their brood with pollen and nectar.
Bees are a derived, herbivorous group of the sphecid wasps.
3.4.2
Bees
Bees, the dominant pollinators in most communities (Proctor et al., 1996),
are speciose, widely distributed, and highly reliable and efficient because a
females collect both nectar and pollen to feed their offspring. For most other
flower visitors, pollen collection is accidental. Social bees (which are a
minority among bees) need additional nectar energy to warm the nest and
speed brood development (Heinrich, 1975). Endothermy allows faster forag-
ing and makes bees important pollinators in cool temperate zones, but
increases their energy requirements. The highly efficient recruitment behav-
iour of honeybees and stingless bees ensures that good nectar sources are
exploited rapidly and surplus nectar can be accumulated (Visscher & Seeley,
1982; Nieh et al., 2003). Colonies focus on the best nectar sources in a large
area by working relatively few patches at any one time and frequently ad-
justing the number of foragers at those patches (Visscher & Seeley, 1982).
Social bees are major pollinators in European and North American systems,
but less abundant in the southern hemisphere systems (Johnson & Steiner,
2000; Ollerton et al., 2006). The highly eusocial honeybees have long-lived
colonies and require a succession of flowers throughout the year, so as a
result are the ultimate generalists among bees (Westerkamp, 1991). Although
they collect from unrelated plants (termed polylectic), flower constancy results
in temporary specialization at the level of the individual insect (reviewed by
Chittka et al., 1999; see also Dafni et al., 2005). When solitary bees are oli-
golectic, gathering pollen from a few closely related taxa, they are less
specialized on nectar. The two introduced bee species that have been most
adaptable in colonizing new habitats around the world are
Apis mellifera
and
Bombus terrestris
, both opportunistic generalists that may potentially com-
pete for nectar with large numbers of solitary bee species (Goulson, 2003).
Of the 20,000 species of bees, almost all provision their young with nec-
tar and pollen. A few mix pollen and floral oils (Buchmann, 1987). The pro-
visioning
of offspring dominates the lives of female bees. Their activity
patterns, and therefore the time required to provision cells, are structured by
a combination of abiotic factors (especially temperature) and the availability
of floral resources (Willmer & Stone, 2004). Solitary bees usually collect pollen