ENTOMOLOGICAL NEWS. 35 



species and embraces the years from 1831 to 1851. The results 

 are summarized in the two chief works of this period Mono- 

 graphic dcs Libellulidees d' Europe, Paris, 1840, and Revue dcs 

 Odo)iatcs on Libcllulcs </' A'tt rope, Brussels, 1850. The Mono- 

 graphic was undertaken chiefly to co-ordinate the work of his 

 predecessors, Vandei Linden ( 1820, 1825 ), Hansemann ( 1823 ), 

 Charpentier (1825), Fonscolombe (1837, '38), Leach (1815), 

 Stephens and Curtis, most of whom had publishd in ignorance 

 of the results of the others. The Revue was a complement and 

 supplement to the Monographic, and is also important as mark- 

 ing the beginning of that co-operation with H. A. Hagen, of 

 which de Selys wrote in 1895, " I owe much to his friendship, 

 to his communications and to his collaboration during the fifty 

 years through which our intimate relations have lasted without 

 interruption." Their correspondence began in 1841 ; in the 

 Spring of 1843 they met in Paris and soon after Hagen offered 

 his co-operation to de Selys. " This precious offer" was thank- 

 fully accepted. The story is told in the "Avertissement" to 

 the Revue. 



The second period is that of the monographic revision of the 

 Odonata of the world. It may be dated from 1853 to 1886. In 

 the Revue, de Selys had given notice of his intention to extend 

 his researches to the exotic forms. He had already acquired 

 the collections of Latreille, Rambur, Audinet-Serville and 

 Guerin-Meneville with this end in view. The first fruits were 

 the Synopsis dcs Calopterygines , 1853, a synopsis as well of the 

 Monographic dcs Caloptcrygincs, with Hagen' s aid, of 1.^54. 

 The latter, said the authors in their preface, 



" is in our thoughts only the commencement of a I listory of the O Ion. it, i 

 that we hope to bring to an end in a few years. Our project is to publish 

 successively, under the form of monographs, the five or six subfamilies 

 that constitute the Odonata, and of which we already know about a 

 thousand species." 



The Synopsis (1854; and Monograpliic dcs (ioinphines > i S v s,s < 

 followed, the latter three years later than expected. Five in- 

 installments of the Synopsis dcs . Igr/onii/cs > iS(, ( ,-65 ) left lh:it 

 group unfinished. Hagen, who had drawn the illustrations for 

 the two preceding monographs. al>o made main- for the pro- 



