Revision of type and non-type material assigned to the genus Orthocladius by Goetghebuer (1940 - 1950), deposited in the Royal Belgian Institute of Natural Sciences (Diptera: Chironomidae) Author Magoga, Giulia ) &) &) Università degli Studi di Milano, Dipartimento di Scienze Agrarie e Ambientali (DISAA), via Celoria 2, I 20133, Milano, Italia; e-mails: giulia. magoga @ unimi. it; matteo. montagna @ unimi. it Author Montagna, Matteo ) &) &) Università degli Studi di Milano, Dipartimento di Scienze Agrarie e Ambientali (DISAA), via Celoria 2, I 20133, Milano, Italia; e-mails: giulia. magoga @ unimi. it; matteo. montagna @ unimi. it Author Marziali, Laura ) &) Water Research Institute, National Research Council (IRSA-CNR), Via del Mulino 19, I 20861 Brugherio (MB), Italy; e-mail: marziali @ irsa. cnr. it Author Rossaro, Bruno ) &) Università degli Studi di Milano, Dipartimento di Scienze per gli Alimenti, la Nutrizione e l’Ambiente (DeFENS), Via Celoria 2, I 20133 Milan, Italy; e-mail: bruno. rossaro @ unimi. it Author Disaa text Acta Entomologica Musei Nationalis Pragae 2017 Acta. Ent. Mus. Natl. Pragae 2017-12-31 57 2 723 749 http://dx.doi.org/10.1515/aemnp-2017-0097 journal article 10.1515/aemnp-2017-0097 0374-1036 5318416 638421F2-985E-43CC-8438-E871F96B1DB8 Cricotopus ( Paratrichocladius ) skirwithensis (Edwards, 1929) Spaniotoma ( Trichocladius ) skirwithensis Edwards, 1929: 329 . Orthocladius nigritus Goetghebuer, 1938: 459 not Orthocladius nigritus Malloch, 1915: 525 , syn. nov. (permanently invalid as junior primary homonym). ? Paratrichocladius nigritus (Goetghebuer) : LANGTON & VISSER (2003) , pupal exuviae. ? Paratrichocladius nigritus (Goetghebuer) : LANGTON & PINDER (2007) , adult male. Paratrichocladius spiesi Ashe & O’Connor, 2012: 492 , syn. nov. (replacement name for Orthocladius nigritus Goetghebuer, 1938 ). Type material examined. Orthocladius nigritus : HOLOTYPE : ♁ stored in isinglass, now mounted on slide, labelled ‘ Orthocladius nigritus n. sp. // type ♁ / M. Goetghebuer // locality Basse Autriche 1938, t 23°// R .I.SC.N.B. 18.073 / Coll. et det. M. Goetghebuer’. Comments. The specimen fits well with C. ( P .) skirwithensis (Edwards, 1929) ; therefore, we propose to synonymize O. nigritus Goetghebuer, 1938 (not Malloch, 1915) with C. ( P. ) skirwithensis . Consequently, its replacement name P. spiesi Ashe & O’Connor, 2012 also becomes a junior synonym of C. ( P. ) skirwithensis . LANGTON & VISSER (2003) and LANGTON & PINDER (2007) separated the respective pupae and adult male of Paratrichocladius nigritus (Goetghebuer) and of P. skirwithensis (Edwards) . Unfortunately, the delimitation of species within the subgenus Paratrichocladius is still controversial, many species are probably present, but morphological evidence should be supported by DNA sequences, because of intraspecific variability ( CRANSTON & KROSCH 2015 , MONTAGNA et al. 2016 ). The small differences described in pupal exuviae ( LANGTON & VISSER 2003 ) do not justify the separation of two species, and this is supported by the examination of the adult male of O. nigritus , which cannot be separated from C. ( P. ) skirwithensis . It is thus not recommended to increase species names and the present decision of synonymizing O. nigritus sensu Goetghebuer with C. ( P. ) skirwithensis results in the synonymy of P. spiesi with C. ( P. ) skirwithensis .