The evidence of the comedies suggests a formal structure — perhaps conventional in earlier Old Comedy — which Aristophanes, at any rate, felt able to modify at pleasure. This formal structure is most complete in Wasps: certain components, in other plays, are either truncated or omitted. The structural elements are these:

(1) Prologue: the tragic prologue is defined by Aristotle (Po. 1449a 4) as ‘all that precedes the entry of the chorus’, and the same definition applies here. Aristophanes’ prologues introduce us to the theme and (directly or indirectly) to the ‘hero’. Dikaiopolis and Praxagora are ‘on stage’ from the beginning, with monologues that set the scene (the Pnyx, A. 20) or hint at a woman’s plot (E. 17, cf. L. 13, 39): so is Strepsiades, who informs us of his troubles (C. 5 ff.), and, in conversation with Pheidippides, of his plan to overcome them (107: cf. Euripides to Mnesilochos, T. 82 ff.). A dialogue between slaves — in Plutus, Karion’s monologue, 1 ff. —prepares us for the first sight of their masters: Philokleon is real to us (W. 87 ff.) before we see him (144), as is Trygaios (P. 54 ff.) before bis entry (62), and in both plays a slave undertakes the exposition of the ‘story’ (λóγoς) for the spectators (W. 54, P. 50: cf. Euelpides in Birds 30-48). Similarly, Demosthenes and his fellow-slave in Knights prepare us for the hated Paphlagonian, and the intended allegory is shown straightaway by a reference to Pylos (55).