As I have verified on material from the NHM (London), a valid name needs to be found for a species in Chironomus that has been misidentified as C. inermifrons Goetghebuer by subsequent authors (e.g., Edwards 1929, Macan 1949 [det. Freeman], Pinder 1978, Lindeberg & Wiederholm 1979, Langton & Pinder 2007); see also Jon Martin's web page http://www.genetics.unimelb.edu.au/Martin/Chironfile/I.htm (http://www.genetics.unimelb.edu.au/Martin/Chironfile/I.htm) . In the Fauna Europaea database (FaEu; chironomid data by Sæther & Spies 2013), technical limitations have allowed this species to be included only under an unavailable pseudonym (so far "C. inermifrons Pinder").
As stated in FaEu, the name Chironomus inermifrons Goetghebuer, 1921 is (A) invalid as a junior homonym, and (B) according to its type material (IRSNB, Brussels) now belongs to Glyptotendipes. Due to persistent problems with the taxonomy in the latter genus (see, e.g., Spies & Sæther 2004), the valid name for Goetghebuer's type specimens remains to be determined.
The adult male of "C. inermifrons" auctorum has some morphological features known from rather few other species in Chironomus; for example, the frontal tubercles are very small (up to 10 μm in height and circumference) or even absent (Langton & Pinder 2007), and apparently there are no acrostichal setae.
For citations of all works referred to here, see http://literature.vm.ntnu.no/Chironomidae/ (http://literature.vm.ntnu.no/Chironomidae/)
A good candidate for a valid name for Chironomus "inermifrons Goet." sensu auctorum is C. longiforceps Kieffer, 1918, which has been treated as a nomen dubium for a long time but is a nomenclaturally available name that may be revalidated. Kieffer described Ch. longiforceps from two adult males collected by W. Horn in August of 1916 near Ignalina in eastern Lithuania. The two syntypes are missing (they have not been found among the Horn/Kieffer specimens at SDEI in Müncheberg, Germany), but Kieffer's description fits the species in question here reasonably well, including the statement "frontal tubercles absent."