Megalothorax

Key to the species of Megalothorax with smooth mucronal lamellae

1. Mucro elliptical with wide and wavy lamellae............................................................... 2

- Mucro not elliptical, with thin lamellae (no part of the mucro being clearly wider than basis)......................... 4

2. Head and trunk with coarse granules and a complex and dense network of integumentary channels; basomedian fields of labium with 1+1 chaetae; tenaculum with 4+4 teeth........................ M. granulosus Schneider & D’Haese, 2013 (Chile)

- Integument with thin granules; tenaculum with 3+3 teeth...................................................... 3

3. Basomedian fields of labium with 1+1 chaetae; ventral, post-labial region of head with 3+3 chaetae, the 1+1 external chaetae being clearly longer and thicker than the 2+2 median, short chaetae; sternum Abd. IV with 2+2 chaetae clearly stronger than chaetae on sternum Abd. VI............................................. M. rubidus Salmon, 1946 (New Zealand)

- Basomedian fields of labium with 3+3 chaetae; ventral, post-labial region of head with 3+3 thin and long chaetae, subequal; sternum Abd. IV with 2+2 chaetae only slightly longer than chaetae on sternum Abd. VI and subequal in length................................................................................... M. aquaticus Stach, 1951 (Poland)

4. S-chaetae S1 and S4 missing on Ant. III.............................. M. poki Christiansen & Bellinger, 1992 (Hawaii)

- S-chaetae S1 and S4 present on Ant. III.................................................................... 5

5. Inner chaetae of sf2–6 with globular shape................................................................. 6

- Inner chaetae of sf2–6 either flam-shaped or T-shaped........................................................ 8

6. Labrum with forked chaetae a1; posterior lamellae of mucro usually smooth, potentially with irregularities or very thin teeth............................................................. M. piloli Christiansen & Bellinger, 1992 (Hawaii)

- Chaetae a1 of the labrum not forked; posterior lamellae of the mucro smooth with distal notch........................ 7

7. Globular organ between antennae present, tenaculum with 3+3 teeth; labral chaetae a2 with 2 clear teeth........................................................................................ M. interruptus Hüther, 1967 (Sudan)

- Globular organ between antennae absent, tenaculum with 4+4 teeth; labral chaetae a2 with very faint teeth (almost smooth).. M. laevis Denis, 1948 (Intertropical zone)

8. Chaeta X on Ant. IV absent, anterior integumentary channels on head covering the clypeal area with multiple forks....... 9

- Chaeta X on Ant. IV present, anterior integumentary channels on head simple and not reaching the clypeal area......... 11

9. Integumentary process in position of chaeta X on Ant. IV absent, Ant. III with 6 ordinary chaetae; dorso-anterior chaeta a0 missing, replaced with integumentary, oval protuberance.............. M. sanctistephani Christian, 1998 (Austria, France)

- Integumentary process in position of chaeta X on Ant. IV present, dorsal, dorso-anterior chaeta a0 present, oval protuberance missing............................................................................................ 10

10. Ant. III with 8 ordinary chaetae; Ant. IV with 4 ordinary chaetae; chaeta β4 on abdomen present; inner chaetae of sf6 candlelight-shaped.......................................... M. tuberculatus Deharveng & Beruete, 1993 (France, Spain)

- Ant. III with 9 ordinary chaetae; Ant. IV with 6 ordinary chaetae; chaeta β4 on abdomen absent; inner chaetae of sf6 T-shaped................................................................ M. dobsinensis sp. n. (Slovakia, MSS, caves)

11. Dorso-posterior chaetae on head thin or ordinary, subequal to anterior chaetae.................................... 12

- Dorso-posterior chaetae on head thickened, stronger than anterior chaetae....................................... 14

12. Dorso-posterior chaetae on head thin and short; abdomen with peculiar pattern of granulation; unguis of ordinary shape............................................................ M. svalbardensis Schneider & D’Haese, 2013 (Svalbard)

- Dorso-posterior chaetae on head ordinary; no specific pattern of granulation on abdomen........................... 13

13. Whitish, with black and brownish dots of pigmentation; channels on head without circles; unguis elongated.............................................................................. M. tatrensis Papáč & Kováč, 2013 (Slovakia)

- Adult with deep red pigmentation; channels on head forming a network; unguis ordinary................................................................................ M. sanguineus Schneider, Porco & Deharveng, 2016 (France)

14. sf3–6 each with at least 1 T-shaped inner chaeta, other inner chaetae candlelight-shaped; Abd. I–V terga with 20+20 chaetae (α–η rows)............................ M. minimus Willem, 1900 sensu Schneider & D’Haese (2013) (Cosmopolitan)

- Inner chaetae of sf2–6 flam-shaped...................................................................... 15

15. Dorsal, posterior region of head with lanceolate macrochaetae, thorax with enlarged macrochaetae; clypeal area with chaetae on integumentary protuberance in front of chaeta a0 ............ M. potapovi Schneider, Porco & Deharveng, 2016 (Russia)

- Dorsal, posterior region of head and terga of thorax with ordinary or thickened chaetae; clypeal area without chaetae on integu- mentary protuberance in front of chaeta a0 ................................................................ 16

16. Inner chaetae of sf6 long; maxilla outer lobe with 1 sublobal hair; unguis ordinary.......................................................................................... M. willemi Schneider & D’Haese, 2013 (Cosmopolitan)

- Inner chaetae of sf6 short; maxilla outer lobe with 2 sublobal hairs; unguis elongated............................................................................................... M. carpaticus Papáč & Kováč, 2013 (Slovakia)

Megalothorax sp.

Source: Deharveng & Bedos (1988), Rigal & Maffre (1988), Bedos (1994), Wiwatwitaya & Takeda (2005). Distribution in Thailand. Chiang Mai, Chiang Rai (N), Nakhon Ratchasima (NE), Phang Nga (P). Habitat: cave in Chiang Rai and Phang Nga provinces (Deharveng & Bedos 1988, Rigal & Maffre 1988); soil s.l. in dry evergreen lowland forest in Nakhon Ratchasima province (Wiwatwitaya & Takeda 2005).

Genus Megalothorax Willem, 1900