Host plants and nymph morphology of an endemic treehopper, Pyrgonota bifoliata, in the Mount Makiling Forest Reserve, Luzon, Philippines

Pyrgonota bifoliata (Insecta: Hemiptera: Membracidae) is a distinct endemic Philippine treehopper species complex distinguished by its extremely elevated and bifurcated pronotal structures. An earlier study suggested that P. bifoliata is a host specialist that feeds on Bridelia (Phyllanthaceae) in northern Luzon and Rubus (Rosaceae) in southern Mindanao. However, the host plant range across the geographical distribution of the P. bifoliata species complex is still poorly understood. In this study, field observations and DNA barcoding were performed to determine the host plant range of P. bifoliata in the Mount Makiling Forest Reserve of Laguna Province on the island of Luzon. The morphology of the last-instar nymph of P. bifoliata was described to facilitate the identification of the species and its host plants. Behavioural interactions between P. bifoliata and its associated ants were also recorded. The results revealed that Piper umbellatum (Piperaceae) and Saurauia latibractea (Actinidiaceae) were the major host plants used by both nymphs and adults of P. bifoliata. The findings indicate that P. bifoliata in the Mount Makiling Forest Reserve of central Luzon is a polyphagous host generalist that primarily utilises two distantly related plant species. The adults of P. bifoliata also occur on Alangium longiflorum (Cornaceae) and Ficus ulmifolia (Moraceae). The nymphs of P. bifoliata are gregarious in small groups and visited by three ant species (Crematogaster sp., Pheidole sp. and Technomyrmex sp.); however, the adults of P. bifoliata are solitary and are never observed with ants. Unlike other treehoppers that are subsocial, the females of P. bifoliata exhibited no maternal care behaviours, such as egg or nymph guarding.双叶角蝉（Pyrgonota bifoliata，昆虫纲：半翅目：角蝉科）是一类独特的菲律宾特有角蝉物种复合体，其显著特征为极度隆起且二叉状的前胸背板结构。此前一项研究指出，双叶角蝉为寄主专性昆虫，在吕宋北部取食五月茶属（Bridelia，叶下珠科）植物，在棉兰老岛南部则取食悬钩子属（Rubus，蔷薇科）植物。然而，目前学界对该物种复合体整个地理分布范围内的寄主植物范围仍知之甚少。本研究通过野外观察与DNA条形码技术，明确了吕宋岛拉古纳省马基林森林保护区内双叶角蝉的寄主植物范围。本研究还描述了双叶角蝉末龄若虫的形态特征以辅助物种鉴定，同时记录了该角蝉与其伴生蚂蚁的行为互动。研究结果显示，大叶胡椒（Piper umbellatum，胡椒科）与宽苞水东哥（Saurauia latibractea，猕猴桃科）是双叶角蝉若虫与成虫共同的主要寄主植物。该结果表明，吕宋中部马基林森林保护区内的双叶角蝉为广食性寄主昆虫，主要利用两种亲缘关系较远的植物作为寄主。双叶角蝉成虫还会见于长花八角枫（Alangium longiflorum，八角枫科）与榆叶榕（Ficus ulmifolia，桑科）植物上。双叶角蝉若虫以小型群居方式活动，会受到3种蚂蚁（举腹蚁属Crematogaster sp.、大头蚁属Pheidole sp.以及狡臭蚁属Technomyrmex sp.）的造访；但双叶角蝉成虫为独居性，从未观察到其与蚂蚁共存的情况。与其他具有亚社会行为的角蝉不同，双叶角蝉的雌虫不存在护卵或保护若虫等亲代抚育行为。