Betula (Betulaceae), or birch, is a Holarctic genus of trees and shrubs whose species have ornamental, industrial, and medical importance. Gall midges of the genus Massalongia (Diptera: Cecidomyiidae: Cecidomyiidi) are exclusively associated with birches in the Palearctic region. In 2018, an undescribed Massalongia species was discovered forming leaf galls on the midveins of B. grossa on Mount Tara, Saga Prefecture, Kyushu, Japan. In this study the species is described as M. nakamuratetsui Elsayed & Tokuda, sp. nov., and a DNA barcode provided for it. The other known species of Massalongia are redescribed because the original descriptions are outdated and insufficient. A lectotype is designated for M. bachmaieri. In addition, the monotypic genus Apagodiplosis, containing A. papyriferae associated with B. papyrifera in the Nearctic region, is synonymized here under Massalongia, resulting in M. papyriferaecomb. nov., rendering Massalongia a Holarctic genus with six species. Comparing the sequence data of M. nakamuratetsui with all sequences available in The Barcode of Life Data (BOLD) system supports the occurrence of Massalongia in the Nearctic region and suggest that more species could be discovered there. Massalongia species form leaf or bud galls, and their mature larvae drop to the ground in autumn and overwinter in characteristic waterproof bottle-like cocoons, which is possibly a protective adaptation for pupation in wet and snowy lands. A taxonomic key to all Massalongia species is provided.

中文翻译：

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修订了与桦树相关的 Massalongia 属（双翅目、白桦科），并描述了日本的一个新物种和全球物种的分类学关键。


桦木（Betulaceae）或桦树是全北区的乔木和灌木属，其物种具有观赏、工业和医学重要性。 Massalongia 属的瘿蠓（双翅目：Cecidomyyiidae：Cecidomyyiidi）仅与古北区的桦树相关。 2018 年，在日本九州佐贺县塔拉山的 B.grosa 的中脉上发现了一种未描述的 Massalongia 物种，该物种在其中脉上形成叶瘿。在这项研究中，该物种被描述为 M. nakamuratetsui Elsayed & Tokuda, sp。 11 月，并为其提供了 DNA 条形码。马萨隆吉亚的其他已知物种被重新描述，因为原始描述已经过时且不充分。为 M. bachmaieri 指定了选型。此外，单型 Apagodiplosis 属（包含与近北极地区的 B. papyrifera 相关的 A. papyriferae）在 Massalongia 下同义，导致 M. papyriferaecomb。 11 月，将 Massalongia 变为全北区属，共有 6 个物种。将 M. nakamuratetsui 的序列数据与生命条形码数据 (BOLD) 系统中可用的所有序列进行比较，支持 Massalongia 在近极地区的出现，并表明在那里可以发现更多物种。 Massalongia 物种形成叶瘿或芽瘿，成熟的幼虫在秋季落到地面，并在特有的防水瓶状茧中越冬，这可能是对潮湿和雪地化蛹的保护性适应。提供了所有 Massalongia 物种的分类索引。