Variable wing venation inAgathiphaga(Lepidoptera: Agathiphagidae) is key to understanding the evolution of basal moths

Abstract

Details of the ancestral groundplan of wing venation in moths remain uncertain, despite approximately a century of study. Here, we describe a 3-branched subcostal vein, a 5-branched medial vein and a 2-branched cubitus posterior vein on the forewing of Agathiphaga vitiensis Dumbleton 1952 from Vanuatu. Such veins had not previously been described in any Lepidoptera. Because wing veins are typically lost during lepidopteran evolutionary history, rarely—if ever—to be regained, the venation of A. vitiensis probably represents the ancestral character state for moths. Wing venation is often used to identify fossil insects as moths, because wing scales are not always preserved; the presence of a supposedly trichopteran 3-branched subcostal vein in crown Lepidoptera may decrease the certainty with which certain amphiesmenopteran fossils from the Mesozoic can be classified. And because plesiomorphic veins can influence the development of lepidopteran wing patterns even if not expressed in the adult wing, the veins described here may determine the location of wing pattern elements in many lepidopteran taxa.

The wing pattern of Hydriomena Hübner, [1825] (Lepidoptera: Geometridae: Larentiinae) lacks a predictable relationship with venation

“…In recent years, the relationship between wing pattern and venation has been used to identify potentially homologous pattern elements, primarily in Microlepidoptera (Baixeras, ; Brown & Powell, ; Schachat, , ; Schachat & Brown, , , ). The predictive power of the relationship between wing pattern and venation was confirmed when the wing pattern of mandibulate moths was successfully used to predict the precise location of a plesiomorphic wing vein for Lepidoptera (Schachat & Brown, , ; Schachat & Gibbs, ). Although few lineages of Microlepidoptera have yet been evaluated in this context, wing pattern in Obtectomera other than butterflies has received even less attention, with just two recent studies of moths in the family Noctuoidea (Gawne & Nijhout, ; Schachat & Goldstein, ), only one of which evaluated the role of venation along the entirety of the wing.…”

The wing pattern ofMoerarchisDurrant, 1914 (Lepidoptera: Tineidae) clarifies transitions between predictive models

“…A more recent examination of Agathiphaga vitiensis from Vanuatu found up to 10 M, Cu and A veins reaching the wing margin: 5 M veins, 2 CuA veins, 2 CuP veins and a fused A vein [14]. A branched CuP vein and a fourth or fifth branch of the M vein are unknown outside of Agathiphaga [14], such that the wing venation ground plan for Lepidoptera is usually reconstructed with a three-branched M vein and an unbranched CuP vein [30]. The three M veins visible on the wings of Moerarchis are referred to here as M 1 , M 2 and M 3 ; this terminology is strictly positional as homologies remain unknown between the three M veins in Moerarchis —and all Lepidoptera other than Agathiphaga —and the five M veins in A. vitiensis .…”

“…The three M veins visible on the wings of Moerarchis are referred to here as M 1 , M 2 and M 3 ; this terminology is strictly positional as homologies remain unknown between the three M veins in Moerarchis —and all Lepidoptera other than Agathiphaga —and the five M veins in A. vitiensis . Because plesiomorphic wing veins continue to influence the development of wing pattern even when not expressed in the adult wing [10,11,14], homologies between M veins must be understood in order for findings from taxa such Moerarchis to be placed in broader evolutionary context.…”

“…According to this model, dark and light bands straddle/abut alternating veins along the costal margin of the forewing (figure 1 a ); two recent studies strongly support this model [10,11].

Figure 1.The two versions of the ‘wing-margin’ model, plotted onto the most recent reconstruction of ancestral wing venation for Lepidoptera [14]. The boundary between the costa and dorsum is ambiguous here; the Rs 4 vein is treated as belonging to the costa because of the developmental constraints that it exerts in the Micropterigidae [10,11].

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“…The two versions of the ‘wing-margin’ model, plotted onto the most recent reconstruction of ancestral wing venation for Lepidoptera [14]. The boundary between the costa and dorsum is ambiguous here; the Rs 4 vein is treated as belonging to the costa because of the developmental constraints that it exerts in the Micropterigidae [10,11].…”