X.—A Taxonomic Review of the British Species of <i>Culicoides</i> Latreille (Diptera, Ceratopogonidæ).

Synopsis A taxonomic review is provided of imagines of the forty-one known British species of Culicoides Latreille (Diptera, Ceratopogonidæ). Four species new to science, C. cameroni , C. reconditus , C. segnis and C. machardyi are described from the British Isles. The female of C. poperinghensis Goetghebuer is described for the first time. C. poperinghensis Goetghebuer and C. subfasciipennis Kieffer are recorded as new to the British Isles. C. lupicaris Downes and Kettle is defined anew. Distinguishing taxonomic characters are given for the females of C. achrayi Kettle and Lawson and C. pallidicornis Kieffer. A number of female structural characters of taxonomic importance are discussed and described for all the British species: the antennal sensilla are found to be important as a group character and antennal ratio as a specific or subspecific character. Descriptive notes with relevant taxonomic discussion are given for each species. The paper includes a key to species based on superficial characters and separate keys for each sex based on structural characters.