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ENTOMOLOGY FOR MEDICAL OFFICERS 



There are two families in this order, namely, (i) the 

 Libellulidce, or dragon-flies proper, in which the hind wings 

 are slightly larger than the front wings, and the wings in 

 repose lie horizontal and more or less extended ; and (2) 

 the Agrionidce, or demoiselle-flies, in which the hind wings are 

 the same size as, or slightly smaller than, the front wings, 

 and the wings in repose are laid backwards and lie vertically. 



Order Neuroptera. 



(Gr. vevpov = dL fibre or nerve, in allusion to the great 

 number of nervures, or veins, in the wings, and Trrepov 

 = wing). 



The Neuroptera include the Alder-flies, Snake-flies, Ant- 

 lions, Mantis-flies (which are not to be confused with the 

 Praying Mantids), Aphis-lions or Lacewings, and several 

 other families that have no vernacular names. Some of the 

 latter resemble dragon-flies, from which, however, they can 



Fig. 119.— Larva of an Alder-fly. 



be distinguished by their longer antennae and by the wings 

 not having the break {nodus) in the front margin. 



In this order the mouth-parts are formed for biting, and 

 both adult and larva are rapacious; there are two pairs of 

 transparent net-veined wings of equal size, or the posterior 

 pair slightly the smaller ; the antennae are conspicuous ; and 

 the metamorphosis is " complete." 



The Alder-flies' {Sialidcs) and the Snake-flies {RhiphidiidcB) 

 are almost restricted to the northern hemisphere. In both 

 families the wings in repose lie sloping over the body, as in 

 moths, and their veins are not so numerous as to form a 

 fine lacework ; and the antennas are long and slender. The 



