Hawk moth pollinator of calanthe plantaginea

Moth pollinator 

The visual stimulus such as colour and shape of the flower are important for attracting the pollinators but fragrance is another dominant trait in the flower that attract the pollinators. Some orchid species use fragrance along with size, colour and arrangement for effective attraction of pollinators. The orchids use this stimulus for attracting the pollinators such as bees, moths and butterflies (Dobson et al., 1969). The flower that attract the moth or butterflies have narrow spur and nectar that can be accessed by the long coiled proboscis. The pollinators are also found to visit orchids that are bright pink, red or yellow and purple colour (Mchatton, 2011). Calanthe plantaginea is purplish to pink in color with yellow spot on the labellum. Other features such as long spur and scent production was observed which might have attracted the hawk moth, carpenter bee and other butterfly species to C. plantaginea.

Hawk moths belongs to family Sphingidae and also commonly known as sphinx moths. The hawk moth ranges from small to medium size, stout body, antennae thick and pointed hook at tips. Fast flight, fore wing ranging from 20 to 60 mm, hind wings are shorter. Wings at rest resemble the arrow shaped head, wings can be transparent, silvery, white and dark brown with markings. Abdomen can be tapering at end or blunt, colour of abdomen will vary from green, yellowish, brown with dark colour bands. The colour pattern in hawk moths are vibrant and vary in individual species (Matyot, 2005). Hawk moth are known for their quick flight and long proboscis, it is really difficult to capture a good photograph of this moth during its visit to orchid. Therefore, drawing was the only means to get the perception on how the pollinators look like while visiting the orchids.

References

Dodson, C. H., Dressler, R. L., Hills, H. G., Adams, R. M., & Williams, N. H. (1969). Biologically active compounds in orchid fragances. Science, 164, 1243-1249. 

Matyot, P. (2005). The hawkmoths (Lepidoptera: Sphingidae) of Seychelles: identification, historical background, distribution, food plants and ecological considerations. Phelsuma, 13, 55-80.

Mchatton, R. (2011). Orchid Pollination: Exploring a Fascinating World. Orchid Pollination Ecology, 80(6), 340-349.

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. 

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.

 

Paper Wasp, a pollinator or a food robber of orchid?

 

Parapolybia varia Fabricius

Parapolybia varia (Paper wasps) was observed on Coelogyne stricta and Coelogyne longipes. The Coelogyne species produced sweet exudate which attracted the pollinators. The active visitation of wasp on the orchid was observed during the sunny day. In C. stricta (D. Don) Schltr., other  two wasp Polistes sp., Vespula sp. and a bumble bee were also observed  visiting in search of the sweet exudate at the base of the labellum and column. P. varia was observed scanning the flower, rachis and peduncle for more than 5 minutes or until distracted by biotic or abiotic interference such as wind and or human being. 

The wasp landed on the inflorescence and then move on the labellum, inserting its head in the floral whorl consuming the exudate. When the wasp retreated from the flower, the head or the thorax came in contact with the column removing the pollinia and attaching it on the head or thorax by viscidium. The anther cap weakly covering the pollinia so, it got removed by gentle movement by the wind or the wasp. It was interesting to note that after the attachment of pollinia the wasp usually tend to immediately remove the pollinia using its hind legs. The irritation or the load of the pollinia might have forced the wasp to remove the pollinia rather than transporting it to stigma of other flowers, which is incidental in all cases. The process of pollinia being removed from the column was observed for most of the flower but no pollinia was found on the stigma. Therefore, P. varia can be classified as a Probable pollinator.

According to Cheng et al. (2009) greenish yellow is the dominant colour in Coelogyne species which is related with wasp pollinated orchids and nectar secretion was not reported in the Coelogyne species. In contrast Kumar, Deepika and Raju (2018) stated the wasp are the generalist pollinator that usually explore flowers which provide exposed nectar and have short perianth since they are known to have short tongue. The flowers visited by wasp usually have dull colour such as reddish brown, dirty purple, or dirty brown. Wasp species were found to visit Coelogyne longipes and C. stricta, which have easy accessible nectar. Color of the C. longipes flower was reddish brown that might have stimulated the wasp to forage for food.

Paper wasp head in contact with anther of C. longipes and pollina attached to the leg as it was immediately removing it from its head. It was an interesting observation made from the study and more studies can be done on it to understanding whether the paper wasps might be the confirmed pollinator or food robber of orchids. The food robber insect do not assist in pollination.  

 

 

 

 

 

 

Pollination of Eria Coronaria by Honeybee (Apis cerena)

 

Honeybee (Apis cerena Fabricius)

Apis cerana is commonly known as Asiatic honeybee, it was observed visiting orchid Eria coronaria landing on the labellum and enter the floral whorl to search for food. When the bee enter and exited from the flower, pollinia got attached on the bee thorax along with the anther cap. The gentle movement by bee or wind led to the removal of the anther cap exposing the pollinia set. The bee on its single visit was found to enter more than 2 flowers of the same species. whereby attaching pollinia on to the stigma. 

A. cerena was observed mostly during the warm sunny day and least during cloudy and windy weather conditions.  E. coronaria was visited only by this pollinator and process of successful pollination was observed. Similar observation have been recorded in China on visitation by Fazhi, Jin, Yuanxin & Yibo (2008). Therefore the pollinator is classified as confirmed pollinator of Eria coronaria Lindl. The orchid seems to cause food-fraud or food deception to attract A. cerana since, no nectar or pollen reward was produced by the orchid.

The success in pollinia transfer by Apis cerana was observed in E. coronaria. The fruiting success was 50% or 100% which signifies that the pollinator is facilitating the successful pollination and fruit set of the orchid. Therefore, the success in fruit set of E. coronaria after the visit by A. cerana also confirms it as the true or confirmed pollinator. 

Photo credit to Tshering Nidup Sir (lecturer, Sherubtse College) who provided the pictures of the honeybee caring pollinia of E. coronaria, (observation made from his personal orchids collections).

References

Fazhi, S., Jin, C., Yuanxin, X., & Yibo, L. (2008). Deceptive pollination of an autumn flowering orchid Eria coronaria (Orchidaceae). Biodiversity Science, 16 (5), 477.