Pelthydrus sculpturatus

Zhu, Bingyue, Ji, Lanzhu & Bian, Dongju, 2018, A new species and a new record of Pelthydrus Orchymont, 1919 from Yunnan, China (Coleoptera: Hydrophilidae: Hydrophilinae), Zootaxa 4438 (1), pp. 189-194 : 191

Key to species of the Pelthydrus sculpturatus group

1. Mentum smooth, shiny with a few independent deep punctures, lateral margins of pronotum straight ........................................... 2

- Mentum with dense punctures, lateral edges of pronotum curved along anterior half ..................................................................... 5

2. Posterior margin of pronotum slightly wider than anterior margin; apex of parameres rounded ..................................................... 3

- Posterior margin of pronotum distinctly wider than anterior margin, apex of parameres oblique and truncated ............................. 4

3. Median lobe shorter than parameres, whose apex slightly pointing towards midline ..................................... Pelthydrus siamensis

- Median lobe longer than parameres, and parameres gradually narrowed from base towards apices ..................................... P. tongi

4. Phallobase longer than parameres; gonopore situated at subapical portion ................................................................ P. sculpturatus

- Phallobase shorter than parameres; gonopore located in the apical position ...................................................... P. ruiliensis sp. nov.

5. Smaller sized species (BL: 2.00– 2.30 mm); apices of elytra narrowly rounded, not meeting at midline ...................... P. kapitensis

- Larger sized species (BL: 2.80–3.10 mm); apices of elytra continuously rounded, meeting at midline .......................................... 6

6. Ground punctures evenly distributed on the pronotum, microreticulation visible; parameres slightly exceeding median lobe ........ ............................................................................................................................................................................................... P. ovalis

- Ground punctures more densely distributed on sides of pronotum, microreticulation almost invisible; median lobe slightly exceeding parameres ............................................................................................................................................................ P. iniquus