The genus Chalepogenus, consisting of 21 species of solitary oil-collecting apid bees, demonstrates oligolecty by foraging on oil-producing flowers from the families Calceolariaceae, Iridaceae and Solanaceae. These oil-flowers are abundant in South America, where Chalepogenus is endemic. In contrast to honey bees, Chalepogenus species do not collect nectar; instead, they gather floral oil for various purposes, including provisioning their larvae, constructing nests, and sustaining foraging adult bees. Although oil collection has been reported to be performed by females only, both males and females have specialised oil-collecting structures.
Distribution
Species of Chalepogenus are restricted to South America.
Morphology
Chalepogenus herbsti (Herbst's Mini-Oil Digger).
Bees belonging to the genus Chalepogenus are relatively small compared to honey bees; their body size ranges from 4.2 to 10.0 millimetres. Chalepogenus species are hairy and exhibit diverse colouration, with some having a black integument (e.g. C. cocuccii), and others displaying yellow markings on their head, thorax, legs, or metasoma (e.g. C. herbsti). Additionally, certain species exhibit red colouring on their legs or metasoma (e.g. C. rufipes), while others have bluish metallic reflections (e.g. C. caeruleus).
The oil-collecting structures (pad and comb) of Chalepogenus bees are covered by setae and are located on the posterior surface of the forebasitarsus. The bees exhibit interspecific variation based on the flower type they forage:
Some Chalepogenus species (e.g. C. rufipes) forage on flowers possessing trichome elaiophores. To do so, they reach the floral oil with their forelegs, making their bulging pad soaked.
Other Chalepogenus species (e.g. C. cocuccii) collect oil from flowers that possess epithelial elaiophores, by sweeping floral oil with their compound comb of setae. These species have a non-bulging pad.
Oil-collecting structures
The oil-collecting structures (pad and comb) of Chalepogenus bees are covered...
