Attraction of males of the cupreous polished chafer Protaetia pryeri pryeri (Coleoptera: Scarabaeidae) for pollination by an epiphytic orchid Luisia teres (Asparagales: Orchidaceae)

Abstract

Males of the cupreous polished chafer Protaetia pryeri pryeri (Janson) (Coleoptera: Scarabaeidae: Cetoniinae) were observed to fly toward, hover around, and land on flowers of an epiphytic orchid Luisia teres (Thunberg) Blume (Orchidaceae). Female chafers were never attracted. When on a flower, a male chafer held the lip with his legs, and then inserted his head deep into the base of the flower column, where pollinia stuck onto his frons. Subsequently some P. p. pryeri males showed pseudocopulation on the lips: downward elongation of the abdomen and extrusion of the copulatory organ. When the chafer carrying pollinia visited another flower, the pollinia were found deposited on the flower stigma. Thus this chafer was considered to be an effective pollinator for this orchid. Males were also attracted to orchid flowers covered with loose cloth that eliminated their visibility, and to a solvent extract of the flower treated on a cotton ball. Therefore, we concluded that the chafer can use olfactory cues released from the orchid flower. Chemical analysis of the nectar secreted from the flower showed that sugar content was about 2–5 %. The pseudocopulation behavior by the pollinator and the presence of nectar on the flower are intriguing and may indicate an evolutionary transitional step between rewarding and rewardless species in deceptive pollination.