NECTAR CONSUMERS - Nectaries and Nectar - page 297

Table 2. A functional classification of flower types and their insect visitors. (From Corbet,
2006.)

Flower types Attributes of visitors Taxa involved

Fully exposed nectar; little
or no intrafloral tempera-
ture elevation; includes
Apiaceae, some Asteraceae

Low flight threshold tem-
perature; little or no endo-
thermy; <30 mg body mass
if hairy, <100 mg if not

Most flies, small beetles,
short-tongued Hymenoptera

Moderate amounts of partly
concealed nectar; often
elevated intrafloral tem-
peratures in sunshine;
includes some Asteraceae,
cup-shaped flowers as in
Rosaceae

Larger insects with moder-
ate flight threshold
temperature

(a) Robust, hairy, endother-
mic insects (some syrphids,
short-tongued bees, larger
beetles)
(b) Slender, poorly insulated
basking insects (some syr-
phids, bombyliids, and
butterflies with low wing
loading)

Flowers with abundant,
deeply concealed nectar,
e.g., Fabaceae, Lamiaceae

Long-tongued, robust,
endothermic insects with
good insulation and high
energy requirements

Long-tongued bees, sphingid
and noctuid moths, butterflies
with high wing loading, a
few syrphids and bombyliids

3.1 Coleoptera

Although beetles are the oldest pollinators (Grimaldi, 1999), they tend to be
clumsy and destructive in flowers. They visit flowers for multiple reasons:
feeding on nectar, pollen, and floral tissue, sheltering for prolonged periods,
or congregating for mating purposes. Nectar feeding by beetles is thus diffi-
cult to observe directly. The chewing mouthparts of beetles limit access to
exposed floral rewards (Proctor et al., 1996), although there are exceptions
to this, as in the large genus Lycus (Lycidae) (Figs. 2 and 4A). In beetle-
flower associations, nectar feeding has been a late development and pollen is
generally more important, as in the bowl-shaped “poppy guild” flowers of
the Mediterranean (Dafni et al., 1990). Similarly, nectar production is sup-
pressed in the African Iridaceae that are specialized for pollination by hopliine
monkey beetles (Goldblatt & Manning, 2006).

Nectar feeding in beetles is probably best known in the subfamily Cetoni-
inae of the Scarabaeidae, partly due to their relatively large size. Cetoniid
beetles are specialized for a diet of nectar and pollen and sometimes petals,
and may even show flower constancy (Woodell, 1979; Englund, 1993), but
are sluggish in their movements from flower to flower (Heinrich & McClain,
1986). Mouthparts of the cetoniid Trichostetha fascicularis lack cutting edges
but bear numerous setae, and dense brushes on the maxillae are used for both