3IOTIONS OF INSECTS. 358 



The LepidopteiYi vary so infinitely in the shape, com- 

 parative magnitude, and appendages of their wings, 

 that I should detain you too long did I enlarge upon so 

 multifarious a subject. I shall therefore only observe, 

 that one species is described, both by Lyonet and De 

 Geer^, as having six wings; for besides the four ordi- 

 nary ones, it has a winglet (Alula) attached to the base 

 of the lower one, and placed, when the wings are 

 folded, between it and the upper. These organs in 

 this order you know are covered with scales of various 

 shape ''. Their nervures are diverging rays, which 

 issue either from a basal area or from the base itself, 

 and terminate in the exterior margin^. The wings 

 of many male butterflies, hawk-moths, and moths, are 

 distinguished by a remarkable, apparatus, noticed by 

 De Geer, and since by many other naturalists'', for 

 keeping tliem steady and underanged in their flight. 

 The upper wings, on their underside near their base, 

 have a minute process, bent into a hook (Ilamus), and 

 covered with hairs and scales. In this hook one or 

 more bristles ( Tendo), attached to the base of the under 

 wing, have their play. When the fly unfolds its wings, 

 the hook does not quit its hold of the bristle, which 

 moves to and fro in it as they expand or close. The 

 females, which seldom fly far, often have the bristles, 

 but never the hook. The hairy tails of some insects, 

 Sesia, Y., belonging to the havvk-moth tribe, are ex- 

 panded when they fly, so as to form a kind of rudder, 



' Lesser, L. i. 109, note ♦. De Geer, ii. 460—. /. ix. /. 9. 

 •• PL4TE XXII, Fig. 7— " Plate X. Fig. 6. 



"* De Geer, i. 173. t. \. f. 4. Linn. Trans, i. 135—. 

 VOL. II. 2 A 



