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Evolution of Insects in terms of the Implicate and Explicate Orders.

Evolution of the flight-function in insects

Part XI
Description of types of flight-devices and flight in insects
Dactylopterygia

( Finger-wingedness )
Examples best expressing type :

Figure 1 :  Orneodes  pygmaea, Ceylon (Sri Lanka), Family Orneodidae (Alucitidae :  Many-plume Moths), Lepidoptera.
(After FLETCHER, in RICHARDS and DAVIES, 1977)

Figure 2 :  Orneodes  desmodactyla, Europe. Wing span 8 mm. The complete set of wings consists of 24 "fingers". Family Orneodidae (Alucitidae :  Many-plume Moths), Lepidoptera.
(After SEVERA, in THIEME's Insektengids, 1977)

Figure 3 :
Left :  Pterophorus  pilosellae, Europe. Wing-span 9 mm. Family Pterophoridae, Plume Moths), Lepidoptera.
Right :  Pterophorus  monodactylus, Europe, Asia Minor, N.America. Wing-span 12 mm.
(After SEVERA, in THIEME's Insektengids, 1977)
Description of the type

Morphological features
Both pairs of wings little different from one another -- homonomy moderately disturbed. Skeleton of thorax and muscular apparatus not investigated, and probably little different from those in  platypterygia. Wings elongate, divided by deep incisions resulting in narrow long lobes ('fingers') (from 2 to 6), each consisting of a longitudinal vein, fringed by the membrane. The wing is covered with long scales -- hairs, especially long at the margins of the lobes. Wing-venation rather rare, not costalized, serving as skeleton of the lobes of the wing. The shape of the body doesn't display special aerodynamic adaptations. Body elongate with long legs.

Functional features
Flight not yet investigated, evaluation of it must be based on indirect considerations. Both pairs of wings participate in wing-beat, thereby do move simultaneously, evident from the presence of a special attaching device (frenulum). Speed of flight and wing-beat frequency not known exactly, but certainly not great. Maneuverability and persistence of flight not investigated. Also absent are data on wing-beat frequency, load, and other parameters of flight features.
These remarkable insects, possessing such an unusual wing structure, forcing to erect for them a special type, undoubtedly realize a flight of a special nature. The main features of dactylopterygia allow them to be compared, on the one hand, with broad-wingedness (platypterygia), and, on the other, with feather-wingedness (ptilopterygia). In all these types the chief direction in evolution consists in maximum decrease of load per unit of wing-surface. This was realized in different ways. Probably, one of the important reasons of these differences were the absolute sizes of the insects, that is, their weight, which is very low in the representatives of feather-wingedness, large in the type of broad-wingedness, and medium in the representatives of the present type, finger-wingedness. See also next Figure.

Figure 4 :  Wings of  Orneodes sp. Family Orneodidae, Order Lepidoptera. (After HANDLIRSCH, in ROHDENDORF, 1949)
Differentiation, connections and representatives of the type.
Dactylopterygia, as such expressed in only a few lepidopterans, namely moths of the families Orneodidae and Pterophoridae, undoubtedly is a derivative of certain forms of broad-wingedness, specifically those that accomplished increase of surface and great lightness by way of developing incisions and appearance of openings in the wing membrane. The narrow distribution (among insects) of dactylopterygia does not allow to note any true differentiation and set up subtypes. In both families all the difference consists in the presence of a smaller or larger number of lobes ('fingers'). The greatest degree of fission of the wing has been accomplished in the family Orneodidae, the least in Pterophoridae. Therefore, the general "surface", better, circumference, of the wings is greatest in forms with highly fissioned wings such as in Orneodidae, rendering this group the most specialized member of dactylopterygia.

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To continue click HERE  for further study of the types of flight-devices in insects, Part XII,  Uropterygia.

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