Identification of genus Heterometrus

Heterometrus, also known commonly as Asian Forest Scorpion, belongs to the family Scorpionidae (the second largest family of scorpions after Buthidae). It is widely considered as a sistergroup to the genus Pandinus (which includes the popular Emperor scorpion, Pandinus imperator). Identification of scorpions is never easy and Heterometrus is no exception. According to Couzijn, 21 species and 31 subspecies is described.

How to recognise a Heterometrus ?
'Identification' of Heterometrus for layman
1) Large scorpion (> 80mm length) usually black, greenish black or dark brown in colour.
2) Large fat pedipalp (pincers) relative to body.
3) 'Tail' or metasoma not very thick.
4) Found in Asia especially South East Asia (tropics)
5) No subaculeus tubercle at the telson (sting). use to differentiate from Diplocentridae.
6) Deep incision present on the mid-rostral part of the prosoma.

A 'typical' Heterometrus (Heterometrus swammerdami or phipsoni?)

The key is extracted from 'Revision of genus Heterometrus' by Couzijn (1981) without his prior knowledge and permission. It is hoped that it will benefit those who are interested and do not have the available resource. If the reproduction of the key infringes upon the copyright of the author, I apologise and would withdraw if the copyright owner explicitly disallows it. The paper (196 pages) provides a much better discussion and I strongly encourage anyone interested to attempt reading it firsthand.

For purpose of webpage comprehensibilty, the key is such that exceptions, exact measurements and trichobotaxonomy may not be included. Those who wishes to know the parameters of trichobothria  measurements may email me. This is regretted as I dislike microscopic examination rarely uses it if possible (despite the well known importance and accuracy of trichobothria identification in arachnids).  Also graphical representation is required to understand the annotations. The type of superciliary crest and pedipalp microsculpture is describe in full as opposed to the presentation in the paper which requires cross reference to 2 other tables.  I have in my discretion rephrase and 'simplify' very few description to my personal preference so I apologise if there's inaccuracies.

The major groups in Heterometrus are as follows:

1) Gigantometrus (swammerdami)  <1 species, 3 subspecies>
- swammerdami swammerdami
- swammerdami flavimanus
- swammerdami titanicus

2) Javanimetrus (cyaneus) <1 species, 3 subspecies>
- cyaneus cyaneus
- cyaneus insulanus
- cyaneus sumatrensis

3) Srilankametrus (indus) <1 species, 2 subspecies>
- indus indus
- indus laevitensus

4) Heterometrus <7 species; 20 subspecies and species>
- laoticus
- spinifer    - spinifer spinifer
          - spinifer solitarius
- petersii    -  petersii petersii
                  - petersi luzonensis
                  - petersii mindanaensis
- longimanus  -  longimanus longimanus
                       -   longimanus tarawakanensis
                       - longimanus humilis
                       - longimanus belitungenesis
                       - longimanus marmoratus
                       - longimanus borneensis
                       - longimanus augustimanus
- madorensis
- bengalensis
- liophysa     - liophysa liophysa
                    - liophysa separatus
                    - liophysa spartanicus
                    - liophysa laevifrons

5) Chernesonesometrus <11 species; 14 species andspecies>
- liurus
- collinus
- pelekomanus
- granulomanus
- tristis
- fastigiosus
- phipsoni - phipsoni phipsoni
                 - phipsoni kanarensis
- scaber  - scaber scaber
              - scaber rugosus
              - scaber obscurus
- xanthopus
- wroughtoni
- fulvipes

Many thanks to Couzijn for clearing up the taxonomic difficulties of Heterometrus.

Key to species and subspecies

1. Very large animal (trunk length 11-15cm) pedipalp hand with almost straight dorsal keel and large proximal lobe, it's external surface is coarsely granulate, not or faintly keeled; teeth of dorsal and lateral metasoma keels numerous, uniform and in a regular line (India, Sri Lanka; (Gigantometrus) swammerdami).................................... (2)
Character combination does not fit ....................................(4)

2. Fine granulation or denticulation present on the (latero) posterior border of mesosomatic sternite IV. Number of teeth per pecten in male >= 20 (India)
..........................swammerdami flavimanus
- (latero)posterior border of mesosomatic sternite IV smooth. no. of teeth per pecten <20 for male ..........(3)

3. External surface of the pedipalp segment IV coarsely granulated . number of teeth per pecten: 18 in male (India)
...................... swammerdami swammerdami
- External surface of pedipalp segement IV smooth or uneven.  number of teeth per pecten < 18 in male .(Sri Lanka)
......................... swammerdami titanicus

4. Superciliary crest anteocular with series of granules and postocular absent (type 4). Pedipalphand microsculpture with reticulation and no recognisable keels (type 7). Size of teeth on lateral mesosomatic keels increasing from basal to the terminal end of metasoma. 4 and 5 postero-inferior telotarsal spines on leg III and IV respectively. (Indonesia (Javanimetrus) cyaneus) .................(5)
- Most of the above but not combination of all ......................(7)

5. Medioposterior borders of mesosomatic tergites I-VI smooth (Madura).......................cyaneus insulanus
- Medioposterior borders of mesosomatic I-VI granulated .......................... (6)

6. Median and posterior areas of the carapace punctuate, as are the mesosomatic tergites; dorsal surface of mesosomatic segment V smooth. Ventral length of pedipalp hand in male: 13mm. slight sexual dimorphism in the ratio of ventral length and maximum width of pedipalp hand (Java, Borneo)
....................... cyaneus cyaneus
- No punctuation on carapace or tergite; dorsal surface of the mesosomatic tergite V mostly furnished with granulation. Ventral length of pedipalp hand in male: 15.4mm. No sexual dimorphism in ratio of ventral length and maximum width of pedipalp hand (Sumatra and Nicobar Island)
................. cyaneus sumatrensis

7. Superciliay crest with no ateocular and postocular part.. Pedipalp microsculpture: granulation present, keels recognisable only from granulation (type 2) or granulation present, keels hardly recognisable, if so with only granulation and reticulation is faint (type 4). Denticulation of lateral mesosomatic keels strongly reduced (Sri Lanka, SE India, Madras (Srilankametrus) indus) ....................  (8)c
- No combination of above ............................ (9)

8. Pedipalp hand microsculpture:  granulation present, keels hardly recognisable, if so with only granulation and reticulation is faint (type 4)  No coarse, distinct granulation on external surface of pedipalp segment IV; ventral intercarinal areas on metasomatic segment V not smooth.(quite a few pairs of hair with granulation as well) (Sri Lanka)
........................... indus indus
- Pedipalp microsculpture: granulation present, keels recognisable only from granulation (type 2); smooth intercarinal areas on metasomatic segment V (except for a pair of hair midway) (India)
....................... indus laevitensus

9. Superciliary crest: series of granules in both anteocular and postocular part (type 6) discontinuous ridge in both anteocular and postocular part (type 5).   Rostrolateral edge of carapace has an distinct incision next to the lateral eyes; pedipalp microsculpture varies (type 6-15) but all does not show keels only recognisable with granulation pattern. No granulation (Eastward of Bangladesh (Heterometrus))....................... (10)
- Superciliary crest with no postocular part. anteocular part subjected to variation (type 1-4). no incision at rostrolateral edge of carapace next to lateral eyes. Pedipalp microsculpture: Not smooth, granulated  with no prominent, contiguous  keels (type 1,2,3,5 and 7) (India (Chersonesometrus))................... (30)

10. Superciliary crest:  Anteocular present (varies) but postocular absent. (type 2,3,4) ................(11)
- superciliary crest: both anteocular and postocular granulated (type 6) or antecular granulated and postocular absent (type 4)...........................(14)

11. superciliary crest: anteocular is a continuous ridge while postocular is absent (type 2) (Thailand)
.............laoticus
- crest: anteocular dicontinuous ridge and postocular absent (type 3) or both anteocular and postocular are discontinuous ridge (type 5) ............................. (12)

12. <concerns distance of trichobothria> (Burma and eastward) ........................ (13)
- <shorter similar trichobothria (Et2 and Dt) parameter> (Sri Lanka)
......................... spinifer solitarius

13. Pedipalp microsculpture: no keels and smooth (type 14). Distinct incision in rostrolateral edge of carapace next to lateral eyes. Angle formed by longitudinal axis of pedipalp segment IV amd line esb1-esb2 (trichobothria) on its external surface : 99º. (Malaysia, Thailand, Cambodia, sporadically in Vietnam)
....................................... spinifer spinifer
- Pedipalp hand microsculpture: smooth with a little reticulation and minimal or no keels (type10). Faint incision on the rostrolateral edge of the carapace next to the lateral eyes. Longitudinal axis of pedipalp segment IV and esb1-esb2 (trichobothria) on its external surface: 62° (Vietnam, sporadically in Cambodia, Thailand)
............................. petersii petersii

14. Pedipalp microsculpture: With reticulation and no recognisable keels (type 7),   granular anteocular superciliary crest with no postocular part.(type 4)
.........................petersi luzonensis
- microsculpture not type 7; superciliary crest: granules on both anteocular and postocular part (type 6)............................ (15)

15. Microsculpture: no granulation at all (type 11 and 12)............................ (16)
- Microsculpture not above .......................... (23)

16. Lateral border of mesosomatic sternites II-IV finely granulated or denticulated.   angle formed by long axis of pedipalp segment IV and line esb1-esb2 on it's external surface: 38º (Mindanao)
.......................petersii mindanaensis
- Lateral border of mesosomatic sternites II-IV smooth.  Angle of long axis of pedipalp IV and line esb1-esb2: 80-96º ............................... (17)

17. Length of ventral side of movable pedipalp degit as a ratio to that of the hand: 1.28 (Philippine island,:Tarawakan)............................. (18)
- ratio as above : 1.13 -1.16 .............................. (19)

18. Carapace granulated all over, as is its medioposterior border; pedipalp with faint reticulation, faint keels which is quite smooth with no granulation.(type 12).   Distinct denticulated protuberance on mesosomatic tergite VII <some trichobothria distance>(Tarawakan)
.................................. longimanus tarawakanensis
- Carapace with smooth areas or smooth medioposterior border; pedipalp pattern: quite smooth with slight reticulation.(type 11)  lateroposterior denticulated protuberance on mesosomatic tergite VII are indistinct <trichobothria measurements> (Luzon)
...................................longimanus humilis

19. <in female, some trichobothria distance>. In male, length of ventral side of the hand: 17.0-17.4mm.  Pectinal shaft total length:9.0mm (Belitung, Bangka, Riau achipelago) ....................... (20)
- not above combination of mentioned length in male (Philippines, Borneo, Bengkalis island near Sumatra) .............................. (21)

20. Distinct incision at the rostrolateral edge of the carapace near the lateral eyes. <trichobothria distance> (Belitung, Bangka)
........................ longimanus belitungenesis
- very faint incision at rostrolateral edge of the carapace next to the lateral eyes <trichobothria distance> (Riau archipelago)
........................... longimanus paris

21. Carapace with smooth areas <trichobothria distance> (Bengkalis island near Sumatra)
................... longimanus bengkalitensis
- carapace granulated all over <trichobothria distance> (Borneo, Philippines) ....................(22)

22. Carapace with marbled colour pattern (Palawan, Balabac)
............................longimanus marmoratus
- Carapace without marbled pattern (Borneo)
................................. longimanus borneensis

23. Pedipalp microsulpture: faint reticulation with prominent contiguous keels (type 13) (Java, Sumatra)........................  (24)
- Pedipalp microsculpture: very prominent coniguous keels with obvious reticulation , granulation may or may not be present (type 6, 8, 9) .......................................... (25)

24. Distinct incision at rostrolateral edge of the carapace next to the lateral eyes. In male, length of internal side of pedipalp segment IV: 12.4mm (Sumatra)
................................. longimanus longimanus
- very faint incision at the rostrolateral edge of the carapace next to the lateral eyes. In male, length of internal side of pedipalp segment IV: 16mm (Java)
........................... longimanus augustimanus

25. Pedipalp microsculpture: reticulated, granulated with prominent, contiguous keels (type 6) (Madura)
..................madorensis
- Pedipalp microsculpture: same as type 6 except that there's little or no granulation (type 8, 9) ...................(26)

26. Pedipalp without granulation (type 9)...........................(27)
- pedipalp with slight granulation (type 8) .......................... (29)

27. Very faint incision at the rostrolateral edge of the carapace next to the lateral eyes.  Relatively small lateral eyes.  Ratio of  pedipalp hand to the ventral side of movable pedipalp digit: 1.15. Angle formed by long axis of pedipalp hand with esb1-esb2 line on external surface: 70º (Burma)
...................bengalensis
- distinct incision at the rostrolateral edge of the carapace next to the lateral eyes. relatively large lateral eyes. Ratio of the hand to the ventral side of the pedipalp digit: 1.17-1.27. Angle of long axis of pedipalp hand with esb1-esb2 line on external surface: 90-114º(Indonesia) ............................... (28)

28. More than 2 prominent teeth on the internal surface of pedipalp segment IV. Ratio of hand to ventral side of the pedipalp digit: 1.27 (Sumatra)
...............................liophysa liophysa
- only one prominent teeth on the internal surface of pedipalp segment IV. Length of hand to ventral side of pedipalp digit: 1.17 (Weh island near Sumatra)
........................ liophysa separatus

29. granulation on the inferior keel of  walking leg femur IV faint or/and sparse <trichobothria measurements> Ratio of lateral keel to length of metasomatic segment V: 2.5 (Babi island near Sumatra)
..........................liophysa spartanicus
- Inferior keel of walking leg femur IV densely granulated <trichobothria measurements> Ratio of lateral keel to length of metasoma V:1.9 (Nias island, Mentawei, Batu archipelago)
.......................liophysa laevifrons

30. Dorsal surface of metasoma smooth (no granules). Ratio of sum of length of metasoma III and IV to median length of carapace: 9.5 ................................. (31)
Dorsal surface of metasoma granulated (ratio as above : 1.04-1.42) ............................ (32)

31. Pedipalp microsculpture (no variation): not smooth with reticulation and absence of keels (type 7) Superciliary crest: discontinuous ridge at anteocular part and absence of postocular part (type 3). frontal area of carapace with partly confluent granules.   No lateral keel s on metasoma V
.........................liurus
- Pedipalp microsculpture: Granulated with absence of keels or keels barely distinguishable from the granules (type 1). Frontal area of carapace finely granulated and are separate and not confluent. lateral keel present on metasoma V
................................... collinus

32. Pedipalp hand very flat and broad. in male, concave external surface; large species. sum of metasoma I-V in male : 53.9mm. female: 48.3mm
..........................pelekomanus
- Pedipalp hand not flatten and broad and external surface certainly not concave; smaller than described above ..................... (33)

33. Pedipalp microsculpture:  granulated with keels recognisable only from granulation (type 2) ................... (34)
- Not type 2 .............................. (35)

34. Superciliary crest: discontinuous ridge at anteocular part with no postocular part (type 3). 3 antero-inferior  spines on telotarsi III, 6 on telotarsi IV
.............................. granulomanus
- Superciliary crest:  granular anteocular part with absence of postocular part. (type 4). 5 anterior inferior spines on telotarsi III, 7 on telotarsi IV
...................................... tristis

35. Pedipalp microsculpture: granulated, reticulated with no recognisable keels. (type 3)
................... fastigiosus
- Not as above .......................... (36)

36. Ventral intercarinal areas of metasoma V smooth (except for a pair of teeth mid section) ............ (37)
- Ventral intercarinal areas of metasoma V granulated .............................. (38)

37. Superciliary crest: series of granules in anteocular and absence of postocular part (type 4) Pedipalp microsculpture: granulated with no or hardly recognisable keels from granulation (type 1)
........................ phipsoni phipsoni
- Superciliary crest: discontinuous ridge at anteocular part and absence of postocular part (type 3) Pedipalp microsculpture: reticulated, with no keels, may be very slightly granulated and is quite smooth (type 7)
...................... phipsoni kanarensis

38. No fine granulation or denticulation on lateral borders of mesosoma sternites II-IV ............................... (39)
- Fine granulation on lateral borders of mesosom sternites II-IV ......................... (41)

39. Pedipalp microsculpture: reticulated, with no keels, may be very slightly granulated and is quite smooth (type 7). Ratio of hand to length of ventral side of movable digit: 1.49 .................................scaber scaber
- Pedipalp microsculpture: granulated with no or hardly recognisable keels from granulation (type 1) or granulated with no keels and very slight reticulation (type 5). Ratio of hand to movable digit: 1.18-1.24 ............................(40)

40. Pedipalp microsculpture: granulated with no keels and very slight reticulation (type 5). <trichobothria angle) Ratio of lateral keel to metasoma V: 2.5
.................................... scaber rugosus
- Pedipalp microsculpture: granulated with no or hardly recognisable keels from granulation (type 1). <trichobothria angle> Ratio of lateral keel to metasoma V: 1.7
............................... scaber obscurus

41. Size of the terminal tooth of ventrolateral keels of metasoma V equals the size of preceding teeth. <trichobothria measurement>
....................... xanthopus
- terminal tooth of ventrolateral keels of metasoma V distinctly stouter than size of preceding teeth. <trichobothria measurement> ................................ (42)

42. No straight sided, brightly coloured, triangle on medioposterior part of carapace; granulation of inferior keels of walking leg femur IV is faint and/or sparse (basal part smooth).  Medioposterior borders of mesosoma tergites I-VI smooth. slight sexual dimorphism in pedipalp hand shape.
................... wroughtoni
- straight sided, brightly coloured, triangle on medioposterior part of carapace present in most specimens. granulation of inferior keels of walking leg fenur IV is dense and complete. Medioposterior borders of mesosoma tergite I-VI granular. distinct sexual dimophism in pedipalp hand shape
................................. fulvipes

By here, many would be pretty groggy and seeing 'stars'.  Good luck with identification and if you wishes to let me identify for you , please send in the following

1) Close up of the prosoma (dorsal part) in jpeg. <optional but ideal>
2) close up of the pedipalp or just description with information like
    (a) reticulation present, absent or slight
    (b) granulation pattern present, absent or slight
    (c) keels visible, slight or absence; due to granulation or otherwise.
    (d) surface smooth or otherwise.
3) Superciliary crest description (both in front of central eye (anteocular) and behind it (postocular)) include granulation, ridges and continuity
4) Close up of just the last segment of tail before the sting. Both side view and ventral view. <optional but ideal> You may describe it to the best of your ability as well.
5) Size of the scorpion from chelicera to distal end of metasoma V. (estimate would be ok)

All these would help me identify some Heterometrus.  I may require additional info and will ask you specifically once the possibilties is narrowed. I am doing it purely on interest and goodwill and reserves the right not to assist for reasons of my own. I hold no responsibilty for error and would usually identify only up to species level to minimise error from variations.

Mail me at caijw@singnet.com.sg if you wish me to do identification for you.

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