Ctenoiidae beetle visiting vanda cristata

Ctenoiidae beetle

The beetle belongs to family Ctenoiidae visiting orchid Vanda cristata. It was difficult to identify the beetle to its species level, but the studies of beetles in Bhutan have high potential. The beetle lands on the labellum and crawls inside the floral whorl in search of the nectar. When the beetle retreats back its pronutum comes in contact with the pollen cap which led to the attachment of pollinia along with the cap on the pronutum. The beetle was very slow in its movement and during one visit they tend to explore 2 to 3 flower and in attempt to crawl to other flower the anther cap gets removed. The attachment of pollinia on the pronutum was observed but the beetle flew away taking the pollinia. Two other beetle of same species visited flowers whose pollina were already removed but same behavior such as exploring the base of the flower was observed. Since the pollinator was observed only carrying the pollinia on the pronutum from this study the beetle was classified as the Probable pollinator of V. cristata. The beetle pollinated orchids are dull in colour, unpleasant scent and usually have fleshy, flat labellum that is devoid of nectar. Visual cues and olfactory cues were the important component that attracts beetle.

Lema unicolor and Clinteria ducalis were the two beetles species attracted by Luisia curtisii orchid through deceptive mechanism (Pedersen, Watthana, Kocyan & Srimuang, 2013). In the study the ctenoiidae beetle visited the V. cristata, having dull purple colour and fleshy lips. Since no nectar rewards was observed in the orchid the beetle might have been deceive by the orchids as presence of food source. Protaetia pryeri pryeri one of the ctenoiidae beetle (male) is a pollinator of Luisia teres. The orchid provided the pollinator with nectar and pseudocopulation was common since the labellum was perceived as a female (Arakaki et al., 2016).

 The labellum of V. cristata is fleshy and resembling to a beetle however, copulating behavior such as excursion of the reproductive organ on the labellum was not observed. The beetle tend to insert it head deep in the floral whorl which indicates that it is in search of nectar. Therefore food deception mechanism was considered as the mode of attraction of this pollinator. To confirm mechanism of pseudo-copulation in this orchid more studies is required with larger number of beetle specimen.

The beetle observed carrying pollinia on his pronotum during its visit.

References

Arakaki, N., Yasuda, K., Kanayama, S., Jitsuno, S., Oike, M., & Wakamura, S. (2016). Attraction of males of the cupreous polished chafer Protaetia pryeri pryeri (Coleoptera: Scarabaeidae) for pollination by an epiphytic orchid Luisia teres (Asparagales: Orchidaceae). Applied Entomology and Zoology, 1-6.

Pedersen, E. H., Watthana, S., Kocyan, A., & Srimuang, K. (2013). Pollination biology of Luisia curtisii (Orchidaceae): indications of a deceptive system operated by beetles. Plants systematics and Evolutions, 299, 177-185.