View/Open - ResearchSpace - University of KwaZulu-Natal

Study sites and observations
Observations on P. madagascariensis were made at Oribi Gorge, Umtamvuna and
World’s View (near Ferncliff in Pietermaritzburg); a population of P. hadiensis was
studied once at Ongoye Forest. A total of at least 20 hours was spent observing these
species, on various days over a number of years, from 9.00 am to 4.00 pm.
Pollinators
The population at World’s View occurred in rocky grassland and was pollinated by
medium-proboscid nemestrinid fly species (Prosoeca circumdata & P. umbrosa) and
Psilodera valida (Acroceridae). The apinid bee, Amegilla aspergina, also visited
flowers. These observations were made in April after the mass emergence of Prosoeca
spp. Both the fly and the bee species have proboscides that reach nectar easily in the
short corolla tubes, while still permitting pollen carryover on the ventral head and
thoracic surfaces.
More time was spent making observations at Oribi Gorge, which resulted in more floral
visitors being recorded. Populations at this study site were most often in rocky areas
near the river. The apinid bees Amegilla caelestina, A. bothai, A. mimadvena and A.
aspergina, Xylocopa caffra and X. hottentotta were common visitors to P.
madagascariensis; the proboscis lengths of this group are slightly longer than that of
the floral tube, but as the bee settles on the boat-shaped lower lip while probing for
nectar, the head rubs over the sexual organs contained in the lip. The bend in the
corolla tube angles the mouth of the tube downwards, which forces large-bodied floral
visitors to depress the lower lip that contains the stamens and style, as it angles
upwards to access nectar which sits at a slightly higher level at the base of the tube.
Medium- and short-proboscid nemestrinid flies of the genus Prosoeca were frequent
visitors at this study site, with the medium-proboscid flies functioning in the same way
as the apinid bees discussed earlier, while the short-proboscid species match the
corolla tube lengths so as to pick up pollen ventrally on the thorax and abdomen. The
tabanid fly, Philoliche aethiopica, visited occasionally; it had similar proboscis lengths
to that of the apinid bees and medium-proboscid Prosoeca species.
Less frequent visits by shorter-proboscid apinid bees at this site included Thyreus sp.
and Apis mellifera, both of which probed for nectar, while a megachilinid bee species
collected pollen ventrally onto the abdomen. The apinid bee, Allodape pernix, reached
Appendix/ 144
P. madagascariensis