Maritime chironomid midges (Diptera) are diverse, yet these ‘pearls of the ocean’ are little known. Emphasizing Pacific Ocean taxa, we used six genetic markers ( 18S , 28S , CAD1 , CAD4 , FolCOI and COI ) and fossil calibrations to produce Bayesian time‐calibrated phylogenies to date eight independent marine transitions in three subfamilies. Deep nodes involve subfamily Telmatogetoninae (originating mid‐Cretaceous, 101 – 128, 114 Ma), with sister genera Telmatogeton Schiner and Thalassomya Schiner splitting later in the Cretaceous (56–82, 69 Ma). Two transitions in Orthocladiinae involve Clunio Haliday and Pseudosmittia Edwards, dating from the upper Cretaceous, both with Eocene crown groups. In subfamily Chironominae, transitions to marine occur in two tribes. Four transitions occur within the otherwise nonmarine crown groups Kiefferulus Goetghebuer, Dicrotendipes Kieffer, Polypedilum Kieffer and Ainuyusurika Sasa & Shirasaka. Two separate robust clades in tribe Tanytarsini involve: (1) a minor radiation within Paratanytarsus dated to the mid‐Eocene around 43 Ma; and (2) an unexpected but fully supported diversification in Pontomyia Edwards plus Yaetanytarsus Sasa dated to around 47 Ma, with separation of Pontomyia from Yaetanytarsus around 40 Ma. Crown Pontomyia , represented by three species, was estimated to have diverged around 19 Ma, whereas the crown radiation of Yaetanytarsus , with 12 sampled species, dates to the mid‐Eocene. In a comprehensive global review we concisely document new synonymies and new combinations revealed by the study. The evolutionary timing estimate provides insights into the frequency of marine transitions and diversifications in the Chironomidae in association with dynamic oceanic changes during the Oligocene and Miocene.

Skusella Freeman, 1961 (Diptera: Chironomidae, Chironominae), known previously from adults from Australia and Africa, is revised with extended descriptions, including for immature life stages. Skusella is diagnosed based on its type species S. subvittata (Skuse, 1889) from Australia, S. pallidipes (Kieffer, 1921) from the Afrotropical region (the only other originally included species), a second African species S. freemani Harrison, 2002, and S. silingae Tang, sp. n., newly described here from the pupa and adult males from China. The immature stages of Skusella have been known informally for several decades, notably for a characteristic fringe of setae on one or more abdominal pleurae of the pupa, shared only with newly described Paraskusella Cranston, 2018 within the Chironominae. Amongst larvae of Chironomini with 6-segmented antenna, alternate Lauterborn organs and a well-demarcated ventromentum, those of Skusella are distinguishable only with caution due to insufficient reared associations. Unassociated pupal exuviae, tentatively belonging to three unknown new species, are described informally from China, as is a larval type from Africa. Range extensions include for S. freemani, with pupae (newly described here) from Nigeria and Cameroon, at least 5000 km from the type locality in South Africa. A wider distribution of S. subvittata in Australia and Asia is revealed by extensive pupal exuviae sampled from drift.

We provide illustrated dichotomous keys for the identification of final (4th) instar larvae of south-east Asian genera of Chironomidae (Diptera), predominantly from aquatic (freshwater and maritime) habitats. The region considered comprises oriental China, Burma, Thailand, Malaysia (west and east), Brunei, Singapore and Indonesia. Eight subfamilies are represented and phylogenetically validated tribes are keyed. Terminal taxa, listed in the sequence used in this guide, comprise 28 genera of Tanypodinae, 71 of Chironominae, 2 of Podonominae, 1 of Buchonomyiinae, 8 of Diamesinae, 2 of Protanypodinae, 5 of Prodiamesinae, 2 of Telmatogetoninae and 61 of Orthocladiinae. The morphology terminology is standard for larval Chironomidae to which users are referred. Illustrations of selected features are provided as photographs with important details labelled. Short summaries of ecology and concise details of selected species and regional / global distribution are provided in brackets under each entry. Some suspect new synonymy is alluded to, but will be addressed formally in more detail elsewhere.

Six new species of the genus Ablabesmyia are described and illustrated from Oriental China: A. (Ablabesmyia) lyrata sp. n. and A. (Ablabesmyia) pectinata sp. n. each based on the male adult and pupa; and A. (Ablabesmyia) huananensis sp. n., A. (Ablabesmyia) praegracilis sp. n., A. (Ablabesmyia) bifurca sp. n. and A. (Karelia) daiensis sp. n. each based on the male adult. The subgenus Karelia is recorded from China for the first time. In addition, A. (Ablabesmyia) alba Chaudhuri, Debnath et Nandi and A. (Ablabesmyia) maculitibialis Chaudhuri, Debnath et Nandi are redescribed based on the male adult, and new distribution records are given for A. (Ablabesmyia) prorasha Kobayashi et Kubota, A. (Ablabesmyia) amamisimplex Sasa and A. (Ablabesmyia) jogancornua Sasa et Okazawa.