The moths of the British Isles / by Richard South.

  • South, Richard.
Date:
[1907-1909]
Catalogue details

Licence: In copyright

Credit: The moths of the British Isles / by Richard South. Source: Wellcome Collection.

    18/522
    wings eight, but in some genera a rib, or perhaps two, may be absent from the fore or the hind wings ; or an extra rib, some- times two, may be found on the hind wings. These modifi- cations, and others, of the general plan of neuration have been employed as a basis upon which to found genera, or to group them together in classification. Fig. 3 shows the arrangement by which the upper and lower wings of a moth are united in flight. The bristle {frenulum) arising from the base of the hind wing is held in place by the catch {retinaculum) on the costal nervure of the fore wing. It will be noticed that the bristle of the male is longer and firmer than that of the female. The latter, moreover, is 6 9 Fig. 3. Connecting- Bristle and Catch. usually made up of two or more strands ; the catch, too, in the female is on the median instead of the costal nervure. These structures are found on the under side of the wings of most moths, but they are absent in all butterflies. The Emperor, Kentish Glory, and Eggars may be mentioned as examples of moths lacking the connecting bristle, but all these have feather-like antennae, which terminate in a point. The Burnets have the antennae gradually thickened towards the tip (A. Fig. 2), and in this respect are somewhat butterfly-like, but these Fig. 4. The Jug-um, or Yoke. moths have a frenulum. The hind wings of the Swifts, and a few others grouped with them, have twelve veins, and these moths have a jugum, 01 yoke (see Fig. 4). This is a flap-like projection from the inner margin, near the base, of the fore wing ; it may serve to con- nect the wings when the insect flies, but it does not seem to be capable of giving much help in that way.