3. Equal (Æquales). When the four wings are of equal length.—Ex. Libellulina.
4. Unequal (Inæquales). When they are not of equal length.—Ex. Hymenoptera.
C. Complication.
5. Plane (Planæ). Flat wings that are neither plicatile nor tumid.—Ex. Apis.
6. Tumid (Tumidæ). When the membrane between the nervures that form an areolet is bigger than the areolet, which gives it convexity.—Ex. The Serrifera or saw-flies. N.B. The object of this structure is to expose a larger surface to the action of the air.
7. Plicatile (Plicatiles). When the wings at rest are folded in one or more longitudinal plaits.—Ex. Vespa L.
8. Duplicatile (Duplicatæ). When they are folded transversely.—Ex. Coleoptera.
9. Convolute (Convolutæ). When the wings so envelope the body as to give it a cylindrical form.—Ex. Crambus.
10. Incumbent (Incumbentes). Wings which when at rest cover the back of the insect.—Ex. The Noctuidæ, Geometra.
11. Cruciato-complicate (Cruciato-complicatæ). Wings crossed and folded.—Ex. Pentatoma, &c.
12. Cruciato-incumbent (Cruciato-incumbentes). Wings crossed but not folded, and covering the back.—Ex. Apis.
13. Extended (Extensæ). Wings that when at rest do not lie upon the body.—Ex. Libellula, Æshna, &c.
a. Expanded (Patentes). Wings that when at rest are horizontally extended and do not cover each other.—Ex. Libellula, &c.
b. Horizontal (Horizontales). Very narrow wings which when at rest are extended horizontally forming a right angle with the body, and covering the posterior wings.—Ex. Pterophorus[1107].
c. Erect (Erectæ). Wings which when at rest are extended vertically.—Ex. Vanessa, Agrion.
d. Erecto-patent (Erecto-patentes). When the primary wings at rest are erect and the secondary horizontal.—Ex. Hesperia.
e. Connivent (Conniventes). When erect wings are so closely applied to each other that the corresponding margins touch.—Ex. Vanessa.
f. Divaricate (Divaricatæ). When wings at rest are somewhat erect but diverge from each other.
14. Patulous (Patulæ). When wings at rest partly cover each other.
15. Applicant (Applicantes). When wings at rest are parallel with the abdomen.—Ex. Tipula.
16. Divergent (Divergentes). When wings at rest recede from the abdomen.
17. Deflexed (Deflexæ). When wings at rest covering each other are so bent downwards as to imitate a roof, of which their interior margin forms the ridge.—Ex. Homopterous Hemiptera.
18. Reversed (Reversæ). When wings at rest are deflexed, but so that the anterior margin of the inferior projects beyond the anterior margin of the superior.—Ex. Gatropacha quercifolia. Plate [XIV]. Fig. 2.
19. Broad (Latæ). When the interior margin is shorter than the posterior.—Ex. Papilio.
20. Narrow (Angustæ). When the posterior margin is shorter than the interior.—Ex. Heliconius.
D. Shape.
1. Falcate (Falcatæ). Wings having their posterior margin concave, and the posterior angle acute and curved.—Ex. Attacus Atlas. Plate [XIV]. Fig. 4.
2. Digitate (Digitatæ). Wings cleft to the base into several subdivisions.—Ex. Pterophorus. Plate [XIV]. Fig. 3.
a. Radius (Radius). A single subdivision of a digitate wing.
3. Caudate (Caudatæ). When wings terminate in a tail-like process.—Ex. Papilio Machaon. Plate [XIV]. Fig. 1. s.
a. Bicaudate (Bicaudatæ). Having two such tails. Tricaudatæ having three, &c.
E. Surface.
1. Squamate (Squamatæ). Wings covered with minute scales.—Ex. Lepidoptera. Plate [XXII]. Fig. 16. a, b, c, d, &c.
2. Denudate (Denudatæ). When the wings of Lepidoptera appear more or less as if the scales had been rubbed off, either partially or generally.—Ex. Heliconius, Sesia, Zygæna, Nudaria.
3. Fenestrate (Fenestratæ). When one or two definite spaces in a Lepidopterous wing are denuded of scales.—Ex. Attacus Atlas, &c.
4. Bare (Nudæ). When wings have neither perceptible hairs nor scales.—Ex. Coleoptera.
F. Margin.
1. Anterior or Exterior (Anterior or Exterior). The outer margin of the wing, or that from the body. Plate [XIV]. Fig. 1. a.
2. Interior (Interior). The inner margin of the wing, or that next the body. Plate [XIV]. Fig. 1. b.
3. Posterior (Posterior). The terminal margin of the wing, or apex. Plate [XIV]. Fig. 1. c.
4. Plectrum (Plectrum). A marginal bristle stronger than the rest, observable about the middle of the costa and standing out from it.—Ex. Many Muscidæ.
G. Angles.