INTRODUCTION. 
HE British entomologist desirous of obtaining coloured illustra- 
tions of his country's insect fauna finds that, as regards the 
more popular Orders, such as the butterflies and moths, or the 
beetles, ample provision has been made for his wants. Should his 
predilections, however, incline towards Flies (Diptera), the case is 
altogether different. For, with the exception of the excellent 
coloured figures of certain British Diptera contained in Vol. VIII. of 
Curtis's ' British Entomology ' (many of which were published more 
than eighty years ago), and three plates of equally excellent coloured 
figures included in Miss Staveley's ' British Insects ' (London : 
L. Reeve and Co., 1871), no illustrations of British Flies in colour 
are obtainable. It is hoped that the plates in the present work, 
which faithfully depict the natural colours, and many of the external 
structural characters of some of the most interesting and important 
of British Diptera, may do something towards meeting the deficiency. 
Although under the social conditions of modern life Blood- 
Sucking Flies are less troublesome to human beings in the British 
Islands than in some other less highly civilised countries, many of 
the species illustrated in this book still often contrive to make their 
presence inconveniently felt, while others in country districts are 
regular tormentors of cattle and horses during the summer months 
Within the last few years Blood-Sucking Flies have acquired a new 
importance, in view of modern discoveries as to the causation and 
dissemination of certain diseases of man and animals, and although 
no Blood-Sucking Fly is permanently associated with any disease in 
the British Islands at the present day, the British mosquitoes of the 
genus Anoplielcs remind us of the time, still comparatively recent, 
when ague was rife in England, while Stomoxys calcitmns recalls the 
Tsetse-flies of Tropical Africa, and the part played by them in 
sleeping sickness and nagana. 
