AbstractThis account provides a detailed morphological and ultrastructural study of wing‐locking mechanisms (LM) in some aquatic Heteroptera. Scanning and transmission electron microscopy were used to describe the functional significance of macro‐ and microstructures holding wings tightly against the body at rest and those involved in functional diptery in flight. There are two types of LM holding the forewings (hemelytra) at rest: 1) wing‐to‐wing LM, and 2) wing‐to‐body LM. The first type includes the brush‐to‐brush LM, the clavus–clavus clamp and the clavus–clavus locking ridge. The second type includes devices locking the hemelytra to the body: the subcostal border of the hemelytra to the lateral border of mesepimeron, the knob‐and‐socket locking mechanism of the hemelytra, and the clavus‐locking mechanism to the scutellum groove. The hindwing is locked by a pair of microtrichial fields situated on the hindwing‐articulated pad at the basal area of the hindwing and on the thoracic pad in the vicinity of the wing articulation. Morphological and ultrastructural data suggest that different LM are parts of one mechanism holding wings to the body at rest. An additional locking mechanism, connecting the hemelytra with the hindwing, is the only LM providing functional diptery in flight. J. Morphol. 257:127–146, 2003. © 2003 Wiley‐Liss, Inc.