CHAPTER XVIII 



BRITISH SPECIES 



The table of British Species given in this chapter is based 

 mainly on a study of a large collection of British and Continental 

 specimens received by exchange during the past ten years from 

 many kind correspondents, and embracing specimens from almost 

 every country in Europe. It is many years since I collected 

 British Dragonflies in their native land. Some of the rarer 

 species I have never seen alive. Information as to coloration, 

 habits, larvae, etc., has been obtained from the excellent works of 

 Lucas[88], Ris[i33] and from numerous smaller publications. Lack of 

 space forbids the complete description of any species here. Only 

 those characters which I have found most reliable are included. 

 To use the table, the student must first make himself thoroughly 

 conversant with the classification in chap, xiv down to Tribes, 

 as far as this comes within the purview of the British List ; always 

 remembering that the most important characters, without which 

 the specific diagnosis may well go all awry, are therein to be 

 found. The measurements which are given for every species 

 seek to include the extremes of possible variation in size. In the 

 case of closely related species, figures illustrate the most reliable 

 points of difference. In Aeschna and Somatochlom, the form of 

 the male appendages is a sure guide (figs. 170, 174) ; in Sympetrum 

 the hamuli of the male (fig. 176) and the valvula vulvae of the 

 female, though the latter cannot always be seen in dried specimens, 

 unless a chitin preparation be made. Undoubtedly the most 

 difficult genus is Agrion. Here the males may be reliably deter- 

 mined, preferably from newly caught specimens, by the colour- 

 patterns of segments 1-3 (fig. 179). These are, however, subject 

 to individual variation within limits, so that a certain allowance 



