The present volume deals with those Nematocera and Aschiza which were listed but not provided with Data Sheets by Falk (1991). Thus members of the following families are included: Mycetophilidae sensu lato (now five families: Bolitophilidae, Ditomyiidae, Diadocidiidae, Keroplatidae, Mycetophilidae sensu stricto), Trichoceridae, Mycetobiidae (sometimes included in Anisopodidae), Ptychopteridae, Dixidae, Culicidae, Thaumaleidae, Ceratopogonidae, Platypezidae, Phoridae, Lonchopteridae and Pipunculidae; the Atelestidae, included within the Platypezidae by Falk (1991) but now regarded as a family of Empidoidea are dealt with by Falk & Crossley (2005). Thus sixteen currently recognised families, comprising about 1226 British Isles species, are considered here. Two of these families, Ceratopogonidae (161 species) and Phoridae (329 species) are insufficiently known for a full assessment to be attempted and Falk (1991) listed only one and ten species (here increased to 22) respectively in these families. In the remaining families Falk listed 296 species or 40% of the presently known British species of these families. The remaining families of Diptera apart from Nematocera and Aschiza that were not dealt with by Falk (1991) are reviewed in three further parts within the JNCC Species Status Review series.

 

Most members of the Chaoboridae and Bibionidae would not merit inclusion and as these families were not considered by Falk (1991) it has not been practicable to gather data on those few species which might be worthy of inclusion. The Anisopodidae is now restricted to the genus Sylvicola with four species, only one of which might merit inclusion but it has not been feasible to consider it. The Opetiidae includes a single species, formerly included in the Platypezidae, which is generally common and this family is therefore excluded. The families Sciaridae, Cecidomyiidae, Psychodidae, Scatopsidae, Simuliidae and Chironomidae were also not considered by Falk (1991) because of insufficient knowledge of the British distribution of their species and it has not been practicable to include any members of these families here. Rotheray et al. (2001) recommended high status (RDB 1) for Ectaetia christii Rotheray & Horsfield (Scatopsidae), because of its association with sap of Aspen Populus tremula at two sites in Scotland and this should be considered if future evaluation of this family becomes practicable.

 

The state of knowledge of the families dealt with here is very variable. There are national Recording Schemes for the five families of fungus gnats (Bolitophilidae, Ditomyiidae, Diadocidiidae, Keroplatidae and Mycetophilidae), Dixidae, Culicidae and Lonchopteridae and an increasing amount of data is becoming available for these families. The small families Trichoceridae and Ptychopteridae (formerly also the Mycetobiidae and Anisopodidae) are included in the "Crane Fly Recording Scheme". There is now a substantial amount of data relating to the "fungus gnats" (Mycetophilidae sensu lato) due to increased recording effort in recent years and this has facilitated the assessment of the status of species. I have also been accumulating data on Platypezidae for many years and their distribution is becoming better known. The Pipunculidae have received less attention than most of these other groups and it was necessary to devote more time to checking data against collections and consultation with specialists in order to arrive at more reliable assessments of their status.