Abstract
The wing stalk in Diptera is examined, and its structures are re-evaluated and re-interpreted. The non-homology of A2 in Tipulomorpha and "A2" in other Diptera is claimed. Some notes are presented on the higher-level phylogeny of Diptera, especially those concerning Tipulomorpha. The family Trichoceridae is restored among Tipulomorpha, and the Tipulomorpha are re-affirmed as the sister group of the remaining Diptera. The clade Anisopodidae + Culicomorpha + Bibionomorpha is suggested as the sister group of Brachycera.
Highlights
Hennig (1968) published a comprehensive treatment of the evolution of the wing base in Diptera, i.e., the complex of features within the so-called wing stalk, mainly the reduction of A2 and the development of the alula. He concluded that A2 is reduced in Diptera other than Tipulomorpha and only retained as a more or less sclerotised, longitudinal cord separating the upper part of the wing stalk from the alula
He hypothesised that Tipulomorpha (Polyneura in his concept) is the sister group of all other Diptera (Oligoneura). He raised some doubts whether the fold, or vein, arising from the alular cord beyond the alular incision into the anal lobe in many Diptera, sometimes almost attaining the wing margin, should be termed A2
In the cladogram by Wood & Borkent (1989), the family Trichoceridae was separated from the rest of Tipulomorpha and included in the largely polyphyletic “Psychodomorpha”
Summary
Hennig (1968) published a comprehensive treatment of the evolution of the wing base in Diptera, i.e., the complex of features within the so-called wing stalk, mainly the reduction of A2 and the development of the alula. He concluded that A2 is reduced in Diptera other than Tipulomorpha and only retained as a more or less sclerotised, longitudinal cord separating the upper part of the wing stalk from the alula.
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