4 EPHEMERID/E OF THE CHALK STREAMS. 



this much at least will it profit them, that days which are bad 

 fishing days will yet be full of interest, by reason of the many 

 small creatures -which before were unseen and now are revealed. 



The total number of species of the Ephemeridse family 

 knoivn to inhabit this country is forty, varying in size from 

 that of the Mayfly down to a minute insect known as Csenis, 

 which is about the size of any ordinary mosquito. (Csenis is a 

 generic name comprising four separate species.) 



It might perhaps be well at this point to get a clear idea 

 of classification as applied to insects by the scientist. 



As far as the fisher is concerned there are only three items 

 that matter (i) Family, of which there are many, but we 

 are only here concerned with one The Ephemeridae. (ii) 

 Genus. Fourteen distinct genera appear in this country, (iii) 

 Species, of which, as we have already stated, forty are to be 

 found in the British Isles. 



Taking the ordinary green Mayfly as an illustration, we 

 find that it is labelled as follows : 



Family Ephemeridae. 

 Genus Ephemera. 

 Species danica. 



There are three sorts of Mayfly : the other two, of course, 

 belong to the same family and genus, but differ in species. 



Flies of the same genus and different species sometimes 

 differ completely in appearance and colouring ; in other cases 

 they are so closely alike that it becomes possible to group them 

 together under one familiar name such as " Olive," which 

 covers no less than five species of the genus Baetis. , The 

 popular name, Pale Watery, covers four separate species all so 

 much alike as to be practically indistinguishable to the ordinary 

 observer. 



