into two Classes. " clxxxix 



The following formula for dividing the Libellulina into groups, is 

 proposed as provisional only ; but being founded on the acute obser- 

 vations of Leach, Van der Linden, Charpentier, Selys de Longchamps, 

 Rambur and Brulle, it may be considered as expressing the present 

 state of our knowledge of these neglected but remarkably conspicuous 

 and beautiful insects: they inhabit every part of the globe, and the 

 number of species appears to be enormously large. 



Labipalpi biarticulate : ocelli in a triangle : — 

 Anal angle of hind wings rounded in 



both sexes Libellulioe, Newm. 



non Leach. 

 Anal angle of hind wings acute in $ , 



rounded in 9 Corduliad^e, Newm. 



Labipalpi Particulate : ocelli in a line : — 



Eyes contiguous zEschnid^e, Newm. 



Eyes separate Gomphid^e, Newm. 



Obs. — It will be observed that this and the preceding group are 

 new, having hitherto been united : but they seem to me distinctly se- 

 parated, neither am I aware of any species or so-called genera occu- 

 pying debateable ground between them. 



Characters of Perlina. 



Larva aquatic, breathing by external tufted branchiae attached to 

 the leg-bearing segments, with long filiform multiarticulate 

 antennae, strong corneous mordent mandibles, depressed body, 

 broad flattened head, and two long multiarticulate caudal setae : 

 frequents the bottom of clear running streams, secreting itself 

 under stones, and feeding indiscriminately on all minute aquatic 

 animals. 



Pupa closely resembling the larva in form, habits and food, the only 

 conspicuous difference that obtains is the prolongation of the 

 posterior angles of the wing-bearing segments into processes, 

 evidently containing the future wings of the imago. 



Imago with long filiform multiarticulate antennae, corneous masti- 

 catory mandibles, broad flat head, distant hemispherical eyes, 

 equally developed leg-bearing segments, 4 membranous recum- 

 bent but not deflected wings, nearly alike, the hind wings largest 

 and having the greatest diameter at the base, where they are 



XX APPENDIX. B B 



