Synopsis
This document is an update to the end of 2025 of Kidd and Brindle’s 1959 publication The Diptera of
Lancashire and Cheshire, Part I. It is also an extension to cover the Acalyptrates and the Calyptrates. Records
from the NBN Atlas and IRECORD for VCs 58, 59 and 60 were downloaded and reduced to a resolution of 1km2
and 1 year. This yielded 142,827 distinct occurrence records covering 3,633 species, just under half the
Britishtotal. All species are listed with numbers of occurrences in each vice-county, the earliest and latest
years ofoccurrence and a measure of relative regional frequency. Also included are summary tables of
numbers ofrecords and species by taxonomic group and vice-county and graphs of the cumulative numbers of
speciesrecorded since 1900 and numbers of species and records during three periods : historic (1900-1970);
middle(1971 – 2010); and recent (2011 – 2025). Maps of recorded species richness by tetrad are also
provided forthe taxonomic groups in each period, and by hectad over all three periods.

Published April 2026