Key to the species of Ptilomera of Thailand

1. Male (Figs. 10–23).................................................................................... 2

1’. Female (Figs. 24–37)...................................................................................8

2. Fringe of intertwined swimming hairs restricted to a small tuft near the apex of the middle femur................. P. fang

2’. Fringe of intertwined swimming hairs extending more than half the length of the middle femur........................ 3

3. Proctiger with lateral wings very small, present as short as projections basally; central lobe of proctiger beyond lateral wings more than twice length of the lateral wings (Fig. 12).............................................. P. hemmingseni

3’. Proctiger with lateral wings large and well developed; central lobe of proctiger beyond lateral wings less than twice length of the lateral wings (Figs. 14, 16, 18, 20, 22).................................................................. 4

4. Pygophore with a narrow, digitate apex (Fig. 21)................................................... P. tennaserim

4’. Pygophore with a roundly triangular apex (Figs. 15, 17, 19, 23).................................................5

5. Proctiger with the median lobe more or less even with posterior tips of the lateral wings (Figs. 14, 22).................. 6

5’. Proctiger with the median lobe well surpassing the posterior tips of the lateral wings (Figs. 16, 18)..................... 7

6. Pygophore with well-developed median carina on ventral surface (Fig. 15)................................ P. hylactor

6’. Pygophore lacking median carina on ventral surface (Fig. 23)............................................ P. tigrina

7. Pygophore with lateral projections weakly-developed (Figs. 18, 19).......................................... P. kra

7’. Pygophore with lateral projections well-developed, surpassing the lateral wings of the proctiger (Figs. 16, 17)..... P. jariyae

8. Ventrolateral lobe of abdominal segment VII obscure, not produced into a pointed or rounded process when viewed laterally (Figs. 25, 27, 31, 33)...................................................................................9

8’. Ventrolateral lobe of abdominal segment VII well developed, forming a pointed or rounded process when viewed laterally (Figs. 29, 35, 37)..................................................................................... 12

9. Connexival spines stout (Figs. 30–33).................................................................... 10

9’. Connexival spines elongate (Figs. 24–27)................................................................. 11

10. Connexival spine and dorsolateral lobe of abdominal segment VII subequal in length (Figs. 32, 33)................. P.kra

10’. Connexival spines much shorter than the dorsolateral lobe (Figs. 30, 31).................................. .. P. j a r iy a e

11. Connexival spines inflected mesad at base (Fig. 24)..................................................... P. fang

11’. Connexival spines straight, and sometimes crossing (Fig. 26)....................................... P. hemmingseni

12. Connexival spines curved and crossing (Fig. 34)................................................... P. tennaserim

12’. Connexival spines straight (Figs. 28, 29, 36, 37)............................................................ 13

13. Ventrolateral lobe of abdominal segment VII digitate, ventral margin concave (Fig. 29)...................... P. hylactor

13’. Ventrolateral lobe of abdominal segment VII nearly right angled, ventral margin convex (Fig. 37)............... P. tigrina