Preimaginal morphology of Austroscaeva occidentalis (Shannon, 1927) is described for the first time, and the morphology of larvae and pupae of Dioprosopa clavata (Fabricius, 1794) is updated based on material obtained from captive rearing of wild females from Argentina and Venezuela, respectively. We describe the morphology of the third instar larva, head skeleton and puparium using optical microscopy, cryo-scanning and scanning electron microscope. The immature stages of both New World flower fly species are analysed and compared with the known preimaginal morphology of other taxa that belong to the evolutionary lineage of Eupeodes-Scaeva, where Austroscaeva Láska, Mazánek & Mengual, 2018, and Dioprosopa Hull, 1949, form a Neotropical radiation within, together with the genus Notosyrphus Vockeroth, 1969. Larvae of all members of this lineage have abdominal segments 5 and 6 with the tips of the locomotory prominences facing posteriorly, and the anal segment with a characteristic U-shaped grasping organ. Two other larval synapomorphies of this group of genera are the presence of metathoracic setae accompanying ventral sensilla, and the abdominal segments 1–7 with an extra lobe on each locomotory prominence. These two last characters cannot be assessed for Macrosyrphus Matsumura, 1917, and Lapposyrphus Dušek & Láska, 1967, based on published information on larval descriptions. Despite a similar colouration pattern of the fully grown larvae, larval morphology of A. occidentalis and D. clavata are quite distinct. The preimaginal morphology of A. occidentalis has a mixture of morphological characters from the taxa Scaeva Fabricius, 1805, Semiscaeva Kuznetzov, 1985, and Dioprosopa. The larvae of D. clavata show several unique diagnostic features, such as the presence of a slightly serrate outline due to the great development of the segmental spines and a pinnate ornamentation of the setae of its dorsal and dorsolateral sensilla. Regarding their biological cycle, the length of the preadult stages of A. occidentalis is almost 5 days longer than the length observed for D. clavata. In addition, new DNA barcodes are provided for A. occidentalis.

中文翻译：

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关于 Austroscaeva occidentalis (Shannon, 1927) 的 preimaginal 形态的第一个数据和 Dioprosopa clavata (Fabricius, 1794)（双翅目： Syrphidae）的幼虫和蛹的重新描述

首次描述了Austroscaeva occidentalis (Shannon, 1927) 的前成虫形态，根据分别从阿根廷和委内瑞拉圈养野生雌性获得的材料更新了Dioprosopa clavata (Fabricius, 1794)幼虫和蛹的形态. 我们使用光学显微镜、冷冻扫描和扫描电子显微镜描述了三龄幼虫、头部骨骼和蛹的形态。分析了这两种新世界花蝇物种的未成熟阶段，并与属于Eupeodes-Scaeva进化谱系的其他分类群的已知前形态形态进行了比较，其中Austroscaeva Láska、Mazánek & Mengual，2018 和Dioprosopa1949 年的赫尔，与1969 年的Notosyrphus Vockeroth属一起形成新热带辐射。该谱系所有成员的幼虫都有腹节 5 和 6，运动突起的尖端朝后，肛门节具有特征性的 U形的抓握器官。这组属的另外两个幼虫突触是存在伴随腹侧感受器的后胸刚毛，以及腹节 1-7，每个运动突起上都有一个额外的叶。无法为Macrosyrphus Matsumura, 1917 和Lapposyrphus评估最后两个字符Dušek 和 Láska，1967 年，基于已发表的幼虫描述信息。尽管完全生长的幼虫具有相似的着色模式，但A. occidentalis和D. clavata 的幼虫形态却截然不同。A. occidentalis的 preimaginal 形态混合了来自分类群Scaeva Fabricius, 1805、Semiscaeva Kuznetzov , 1985 和Dioprosopa的形态特征。D. clavata的幼虫显示了几个独特的诊断特征，例如由于节段棘的巨大发育和其背侧和背外侧感受器的刚毛羽状纹饰而存在轻微锯齿状轮廓。关于它们的生物周期，A. occidentalis 的前成体阶段的长度几乎比D. clavata观察到的长度长 5 天。此外，为A. occidentalis提供了新的 DNA 条形码。