Pelthydrus jendeki

Bian, Dongju, Schönmann, Heinrich & Ji, Lanzhu, 2009, Five new species of Pelthydrus Orchymont, 1919 from China and adjacent countries (Coleoptera: Hydrophilidae), Zootaxa 2118, pp. 53-64 : 59

Key to Pelthydrus jendeki Group

1. Head and pronotum with double sized punctation; elytra with ten punctate striae .................. Pelthydrus waltraudae

- Head and pronotum without double sized punctuation; elytra without striae .............................................................. 2

2. Larger sized species (more than 3.5 mm); phallobase much longer (approx. 2/3) than median lobe and parameres .. 3

- Smaller sized species (less than 3.5 mm); phallobase shorter or about as long as medianlobe and parameres ........... 4

3. Pronotum and elytra with dense, rough punctation, feeble shining; basal half of parameres robust, distal half very narrow and parallel shaped .................................................................................................................... P. vietnamensis

- Pronotum and elytra with fine punctation, nearly metallic shining; parameres distinctly narrowed towards apical part, apices somewhat oblique at outersides .................................................................................................... P. jendeki

4. About three-fourths of parameres parallel shaped, distal quarter medially rounded, ending with a point at the inner side ................................................................................................................................................................................ 5

- Proximal half of parameres parallel shaped and distal half curved, or complete parameres curved, always ending with a sharp point.......................................................................................................................................................... 6

5. Median lobe very thick, nearly parallel shaped, rounded at the end ........................................................ P. subgrossus

- Median lobe distinctly narrowed from base towards apex, ending with a sharp point................................... P. grossus

6. Phallobase shorter than parameres and median lobe .................................................................................................... 7

- Phallobase almost of the same length as parameres and median lobe.......................................................................... 8

7. Phallobase a little shorter than median lobe and parameres; parameres gradually narrowed from base towards apex, distal half distinctly narrowed, apices somewhat truncated at innersides ............................................................ P. rosa

- Phallobase distinctly shorter than median lobe and parameres; parameres almost equal at basal two thirds, sharply narrowed at distal third and arched towards inner side ............................................................................. P. longifolius

8. Median lobe distinctly widened from base to middle part and then gradually narrowed toward distal part, ending with a pointed apex, distinctly shorter than the S-curved parameres ......................................................... P. yulinensis

- Median lobe almost of the same length as parameres, proximal half of parameres parallel shaped, distal half slightly arched, ending with distinct points .............................................................................................................. P. dudgeoni