The term natural is here employed in the empirical sense described by Brunner von Wattenwyl, Nouv. Syst. Blattaires, 1865, p. vii.
Lord Walsingham, Proc. Ent. Soc. London, 1889, p. lxxx.
We may mention that fossil Insects are chiefly determined from their wing-remains, which are often surprisingly perfect. This is one of the reasons that have induced us to prefer a classification of Insects in which the nature of the wings is considered of great value. It would be impossible to refer fossil Insects to groups that are established on account of the metamorphosis or of the internal structure of their components, for there is not yet any evidence on either of these points in the fossil remains preserved for us by the rocks.
Bull. U.S. Geol. Survey, No. 31, 1886, p. 109.
Mem. Acc. Lincei Roma (4), iv. 1888, p. 543, etc., and other preceding memoirs mentioned therein.