Figure 1.

A set of characters for the maxillae, mandibles, and labial sensilla of Mesovelia (Gerromorpha). (a) The shape of the apex of maxillae, the left apex (axl) is visible, exposed, the ventral rupturing device (brvex) is visible. (b) The straight and narrow apice (ax) of both maxillae (Rmx, Lmx). (c) Right mandibular file (Rmd) consists of seven short spines (sph); the file is of medium length, two rows of spines in the rupturing device: internal (brvin) and external (brvex). (d) Cross-section of maxillae (Rmx and Lmx) and mandibles (Rmd and Lmd). (e) The labial tip with peg, uniporous sensilla (Tp-ps) and subapically placed elongated, multiporous plate sensillum (Wp-ples). (f) An arrangement of the mechanosensilla, several short chaetica sensilla (CH3) on the third labial segment. (g) Numerous chaetica sensilla, long (CH1) and of medium length (CH2) placed on the first and second segment, dorsally. (h) The sensilla are small and a few are present on the third and fourth segments, FC: food canal; SC: salivary canal; depr: dorsal external process, right; vepl: ventral external process, left.