63 



gives illustrations of about nine species, some of the figures 

 being very good. 



Under the title of the Flat Blue-tailed Libella, Moses 

 Harris in the " Aurelian," in 1778, gives a good description 

 and two accurate figures of Lihellnla dcprcssa, one of the 

 figures shewing the imago in the act of emerging. In his 

 " Exposition of English Insects,'' he figures three nymphs, 

 but very poorly compared with those in his earlier book. 



Linnaeus, in his " Systema Naturae," mentions their prey- 

 ing on aquatic insects, and De Villers in his edition of 

 Linnaeus, in 1789, compares them to crocodiles among the 

 water insects. 



Then we find a nymph or two in Donovan (1792-1813), 

 and Evans (1845), but I do not intend now to go fully 

 into the literature of the subject, and shall onty refer further to 

 one or two writers who have attempted to classify certain 

 of the nymphs. Dufour made a slight attempt in 1852, 

 treating, however, of seven nymphs only ; and the first 

 really useful work done was in Brauer's " Neuroptera 

 Austriaca" (1857), though his descriptions are mostly 

 generic. 



In 1872 Mr. L. Cabot, with the assistance of Dr. Hagen, 

 commenced a systematic account of the dragonfly nymphs, 

 and in that year fully described the known species of the 

 sub-families, Goinpliince and CordtilcgastcrincE, accompan5'ing 

 his descriptions with beautiful figures. In 1881 he similarly 

 treated the ^^schnince, and in 1890 the Cordiiliince. Too 

 much praise cannot be bestowed on these productions of 

 the Museum of Comparative Zoology at Harvard College. 



Almost equally good is the treatment of several of the 

 CalopterygtncE and Ai^rionincE by Roster in the "Transactions 

 of the Italian Entomological Society" in 1886 and 1888. Here 

 then, the matter stands, for Nunney's articles in " Science 

 Gossip," in 1894, being little more than a short collation of the 

 writers, especially Cabot and Roster, of whom I have just 

 spoken, helps us but little upon our way. 



Of course it is well-known that to obtain many of the 

 nymphs is not an easy matter, and their identification is 

 often more difficult still. Three methods are available : — 

 I. Isolating them, and carrying them through to the perfect 

 state ; 2. Finding empt}- skins b}' the side of recently- 

 emerged imagines ; j. Finding skins under such conditions 

 that the}' can only belong to insects that are on the wing in 

 the neighbourhood. The first method is most satisfactory, 

 the second fair!)- so, while the third will nearly always 



