乾 陽子

type:Article 飼育下のナミアゲハ幼虫で、餌種を変えると摂食不良を示す場合があることが知られている。行動実験で摂食選好性と産卵選好性を調べた結果、特定のミカン科種への選好性はなかった。ただし、統計的には有意ではなかったものの、摂食してきた餌種と異なるミカン科種に対して選好性が低くなる傾向がみられた。幼虫の飼育実験では、成長パフォーマンスの指標として測定した頭幅・幼虫期間・前蛹重のうち、前蛹重が、餌種の変更によって有意に低下することがわかった。これらの結果から、ナミアゲハの飼育において摂食不良を回避し、安定した羽化にむけて成長させるためには、与える餌は寄主であるミカン科のどの種でもよいが、1種に固定することが望ましいと考えられる。 Larvae of Papilio xuthus in captivity are empirically known to sometimes exhibit reluctance to feed rutaceous leaves, their natural host. Our behavioral experiments on larval feeding and adult oviposition revealed no significant difference in preference between host rutaceous species, although a tendency for a lower preference for host species different from those previously fed on by the larvae. In the larval rearing experiment, among the indicators of growth performance measured, prepupal weight was significantly decreased when the diet host species was changed during rearing compared to when feed on only one host species. To avoid feeding reluctance and promote optimal growth in Papilio xuthus rearing, it is advisable to maintain a consistent diet species.

Abstract Volatile compounds in floral nectar may affect plant–pollinator relationships; however, the understanding of the distribution and functions of scented floral nectar is still relatively limited. In this study, we examined the volatile constituents of the scented floral nectar of the black lily Fritillaria camschatcensis and their potential to attract flower‐visiting flies. In Japan, F. camschatcensis comprises two varieties, var. camschatcensis (lowland) and var. keisukei (alpine). The flowers of both varieties secrete large amounts of nectar that is fed on by visiting flies. We investigated the sugar concentration of the nectar using high‐performance liquid chromatography (HPLC) and studied its volatile chemical composition using gas chromatography–mass spectrometry. We conducted a bioassay using a synthetic mixture of nectar volatiles of the lowland variety to test whether flies are attracted to volatile compounds in the nectar scent. HPLC analysis showed that glucose and fructose occur in the nectar of the alpine variety, whereas the lowland variety nectar contained glucose but lacked fructose. Nectar volatile compounds differed substantially between the two varieties; the volatiles of the lowland variety consisted primarily of four aliphatic acids, whereas acetophenone was the main volatile compound in the alpine variety. The bioassay showed that a mixture of three aliphatic acids detected as volatiles of the lowland variety nectar attracts flies, including those that visit the alpine variety flowers such as Calliphoridae. These results suggest that the volatiles of the scented nectar serve as attractants for flower visitors and may have an important role in the pollination of F. camschatcensis.