12 



extremely aberrant Xycteribida;, which, doubtless, suck blood, but, 

 being exclusively parasitic on bats, are of no practical importance, the 

 blood-sucking habit is met with in only eight. Included in this total 

 are the Psychodidae and Leptidse ; as regards the former, the blood- 

 sucking genus Plilebotoinus does not occur in Great Britain, and 

 although blood has been noticed (by the Rev. A. E. Eaton) in the 

 abdomen of a British specimen of Sycorax silacea, Hal., the insect has 

 not j'et been observed in the act of sucking blood, so that for our 

 present purpose the Psychodida; may be left out of account. The 

 same course may be taken in the case of the Leptida;, for no species 

 of this family has yet been recorded as sucking blood in the British 

 Islands, although in France the common British Leptis scolopacea, 

 Linn, (as also L.strigosa, Mg. — a " reputed " British species) has been 

 observed in the act of doing so on two or three occasions. The 

 number of families of British Diptera that include blood-sucking 

 species is therefore reduced to six, — the Chironomida; (midges), 

 Culicidaj (gnats or mosquitoes), Simulid.c, Tabanidiu (horse-flies), 

 Muscida;, and HippoboscidcX-. In two of these, the Chironomida; and 

 Muscida', the blood-sucking habit is exceptional and confined to a 

 few species ; in the remainder, with the exception of a few small 

 genera of Culicidae, the species of which do not suck blood, it is 

 universal in the female sex, to which, with the exception of the 

 Muscidai (and possibly of the Hippoboscida:), the habit is restricted. 

 It should be noted that most, if not all, mosquitoes are also capable of 

 subsisting upon the juices of plants. 



The number of species of blood-sucking flies that occur in the British 

 Islands cannot be stated precisely, since the total of the blood-sucking 

 species of midges(genus Ceratopogon,sc>is.lnt.)7iX\d that of our indigenous 

 species of Simttliuni is at present entirely uncertain. If, however, we 

 count each of these groups as numbering a dozen species (certainl)- 

 not an extravagant estimate), and include the two species of Nycteri- 

 bida;, the number of British species of blood-sucking flics would 

 amount to 74. The total number of species of Diptera recognised as 

 British at the present time may be taken as between 2700 and 3000. 



With these introductorj' remarks we may proceed to a consideration 

 of the species illustrated in the plates, which represent the principal 

 British blood-sucking flies. 



