Blackbee (Ctenoplectra cornuta) close association with Dendrobium Species

 

Picture by Tshering Nidup Sir (Lecturer, Sherubtse College)

Ctenoplectra cornuta Gribodo

The C. cornuta is one of the small metallic bee species belonging to family Apidae. It seems that these bees are closely associated with Dendrobium Spp. It was observed to visit D. chrysanthum D. hookerianum, Dendrobium nobile and D. aphyllum. Male bee were the most common visitor to the orchids and only one female was observed during the observation period.

The bees were observed landing on the labellum and usually took shelter in the floral whorl. Behavior such as rubbing of the abdomen and the hind legs on the labellum were observed. Frequently, the pollinator was found to place their abdomen inside the floral whorl and the head outside staying in resting position. The bees stayed on the flower for about 20 to 24 seconds rubbing on the labellum and then flew away. During the visit of the bee to other flower and due to the relative position of stigma to anther the pollinia gets attached on to the sticky concave shaped stigma. Thus, pollination takes place due to the floral feature of the orchid and the behavior of the C. cornuta bee. The observation made on the pollinator carrying pollinia and attaching the pollinia on the stigma, ascertaining C. cornuta as Confirmed pollinator of D. hookerianum.

Most of the Asiatic genus of Dendrobium lack nectar so, the common mode of attracting their pollinators is by deception and mimicry. In contrast it was observed that the Dendrobium species can also provide oil and sheltering site for their pollinators (Kjellsson, Rasmussen & Dupuy, 1985). The black bee (C. cornuta) are known to collect oils from the flowers to build the nest and their host plants includes Thladiantha sp., Momordica sp., and orchids from the family orchidaceae (Sung, Dubitzky, & Yamane, 2009).

The bee would just take shelter on the flower for significant time period. Such behavior was due to the presence of oil glands on the labellum which is collect by these bee species. Similar visit and behavior were observed on other two Dendrobium species by the bee but further studies and observation are required to confirm the bee as their pollinator. The process such as the attachment of pollinia and transfer of pollinia to stigma by the pollinator was not observed but visitation to the common genus of orchid by the bee proves the existence of important relationship of the C. cornuta with Dendrobium species.

References

Kjellsson, G., Rasmussen, N. F., & Dupuy, D. (1985). Pollination of Dendrobium infundibulum, Cymbidium insigne (Orchidaceae) and Rhododendron lyi (Ericaceae) by Bombus eximius (Apidae) in Thailand: a possible case of floral mimicry. Journal of Tropical Ecology, 1(4), 289-302.

Sung, I. H., Dubitzky, A., Eardley, C., & Yamane, S. (2009). Descriptions and biological notes of Ctenoplectra bees from Southeast Asia and Taiwan (Hymenoptera: Apidae: Ctenoplectrini) with a new species from North Borneo. Entomology science, 12(3), 324-340.