Checklist of the Cecidomyiidae (Diptera) of Finland

Abstract A list of the 356 species of Cecidomyiidae (Diptera) recorded from Finland is presented, which comprises 6 Lestremiinae, 156 Micromyinae, 16 Winnertziinae, 69 Porricondylinae, and 109 Cecidomyiinae. The faunistic knowledge of Finnish Winnertziinae, Porricondylinae and Cecidomyiinae is regarded as particularly poor. Based on species numbers known from other countries in Europe, a conservative estimate is 700–800 species of Cecidomyiidae actually occurring in Finland.


Introduction
With a world total of more than 6200 species described, Cecidomyiidae are among the largest families of Diptera, although adult cecidomyiids are mostly delicate midges with body lengths of less than 5 mm. The family has been catalogued (Gagné and Jaschhof 2014) and that publication provides bibliographic and other information on all known species. Six subfamilies are recognised: the fungivorous Catotrichinae, Lestremiinae, Micromyinae, Winnertziinae and Porricondylinae, and the mostly herbivorous Cecidomyiinae. The latter subfamily, which also includes fungivores and predators, comprises the largest gall-making group of insects (hence the family name that translates as gall midges).
In the fungivorous subfamilies, many larvae are associated with dead wood, rendering those a biodiverse, albeit little studied group of saproxylic insects. In Cecidomyiinae, larvae associated with living flowering plants are usually restricted to development on one, or a few closely-related host species; predators are also generally assumed to be highly host-specific, as far as is known.
The Palaearctic has more named Cecidomyiidae species than any other zoogeographical region, and the best known gall midge fauna is that of Europe, with more than 1800 species (Skuhravá 2006). Even so, European Cecidomyiidae are far from being completely known, and the Finnish fauna provides a good example. To illustrate, while the previous checklist of Finnish Cecidomyiidae (Hackman 1980) comprised only four species of Lestremiinae and Micromyinae, a recent taxonomic study increased that number to 162, including 34 new species . As for Winnertziinae and Porricondylinae, 27 species in Hackman's (1980) list compare with 69 species recorded here (Penttinen and Siitonen 2005, Penttinen and Spungis 2007, Penttinen and Jaschhof 2009Jaschhof, unpublished;Penttinen, unpublished), yet much remains to be discovered, as is testified by specimens in the Penttinen Collection belonging to a number of unnamed species. In Cecidomyiinae, only three species (Hulden 2003;Skuhravá, unpublished) are here added to the Hackman list, a meager increase that is obviously explained by the slight research effort in recent years.
Identification of cecidomyiids, both larvae and adults, is generally difficult and usually left to a few taxonomic specialists of the family. An adult key to the Palaearctic genera of Cecidomyiidae was provided by Skuhravá (1997); to the Holarctic genera of Lestremiinae and Micromyinae by Jaschhof and Jaschhof (2009), and to the Holarctic genera of Winnertziinae and Porricondylinae by Jaschhof and Jaschhof (2013). Adult keys and illustrations by Jaschhof (2009, 2013) can be used to identify the Finnish species of the fungivorous subfamilies. Adult keys to identify species of Cecidomyiinae in Finland are only available for a few small groups, so any attempts in this regard rely largely on descriptions and illustrations scattered in an extensive literature. In general, many Cecidomyiinae species cannot be identified unless a bundle of information (regarding host, gall, immature stages, adults of both sexes) are known. Illustrated keys to galls, including those caused by gall midges, have been published for Central and Northern Europe by Buhr (1964Buhr ( , 1965, a resource that is currently being revised and updated for publication in English in 2015 (see http:// www.pflanzengallen.de).
The arrangement of taxa in this list largely follows the recent edition of the world catalogue (Gagné and Jaschhof 2014) except that genera are here arranged under their pertinent tribes and supertribes, if known. All Finnish records of species of the fungivorous subfamilies were revised in recent years Jaschhof 2009, 2013;Penttinen, unpublished), so can be related to actual voucher specimens deposited in museum collections. The list of Cecidomyiinae, which is not updated to the same extent, is compiled from published locality records based on varying evidence, including galls alone.