Frustration with Heterometrus revision for ID purposes, and question about juvenlie ID

[SonOfSerket]

Hi, all.

I now own four (I promise I didn't *mean* to buy this little juvenile guy...it just happened, lol) AFS's. I recently posted pics of my adult male, but will repost those here in hopes that you Heterometrus experts will help. I'm a biologist, so I feel pretty comfortable with dichotomous keys, but I get super frustrated with the Prendini & Loria 2020 revision...sure, it's a GREAT resource, and was undoubtedly YEARS of work to produce, but, here are my issues:

#1. Many of the couplets rely on characteristics of adult males only OR mixed couplets with characteristic traits of adult males and completely different characteristics of adult females (if they're included in the couplet at all).
#2. As an extension, many species seem to display sexual dimorphism at least in terms of granulation in terms of degree and location (this is what annoys/stresses me out the most).
#3. I don't *think* there's anything even said about identification of juveniles (of which I have two now, one of each sex), but I also have not read the near 500 page manuscript from beginning to end. CAN juveniles be ID'd to species reliably in any way outside of the key in the 2020 revision? I'd wager that they can, especially by you guys that have extensive experience with the genus, and I'd greatly appreciate the help on how to do so.

I *suspect* I've got at least 2 species represented amongst my four kiddos, *maybe* even 3, but I'm so damn confused and frustrated, I'm almost to the point of just saying I have "4 Heterometrus sp.," but then even typing that makes me lose my mind. I will be in my office soon (where all my arachnids are), and will likely be adding tons of pictures of all of them here in a cry for help from you Heterometrus experts.

Despite my frustration, it's also hard to be too mad about it for too long, as I've fallen in love with this genus and their overall temperament/behavior, as well as the small idiosyncratic differences in "personality" from one individual to the next. I'd just really love to know what species they all are, if possible.

Additionally, I'd also just appreciate further conversations with other Heterometrus afficionados, whether it's for ID tips, or just to wax poetic about why they're pretty great. My apologies for the rant otherwise!

 

[Andrew Clayton]

Hi, all.

I now own four (I promise I didn't *mean* to buy this little juvenile guy...it just happened, lol) AFS's. I recently posted pics of my adult male, but will repost those here in hopes that you Heterometrus experts will help. I'm a biologist, so I feel pretty comfortable with dichotomous keys, but I get super frustrated with the Prendini & Loria 2020 revision...sure, it's a GREAT resource, and was undoubtedly YEARS of work to produce, but, here are my issues:

#1. Many of the couplets rely on characteristics of adult males only OR mixed couplets with characteristic traits of adult males and completely different characteristics of adult females (if they're included in the couplet at all).
#2. As an extension, many species seem to display sexual dimorphism at least in terms of granulation in terms of degree and location (this is what annoys/stresses me out the most).
#3. I don't *think* there's anything even said about identification of juveniles (of which I have two now, one of each sex), but I also have not read the near 500 page manuscript from beginning to end. CAN juveniles be ID'd to species reliably in any way outside of the key in the 2020 revision? I'd wager that they can, especially by you guys that have extensive experience with the genus, and I'd greatly appreciate the help on how to do so.

I *suspect* I've got at least 2 species represented amongst my four kiddos, *maybe* even 3, but I'm so damn confused and frustrated, I'm almost to the point of just saying I have "4 Heterometrus sp.," but then even typing that makes me lose my mind. I will be in my office soon (where all my arachnids are), and will likely be adding tons of pictures of all of them here in a cry for help from you Heterometrus experts.

Despite my frustration, it's also hard to be too mad about it for too long, as I've fallen in love with this genus and their overall temperament/behavior, as well as the small idiosyncratic differences in "personality" from one individual to the next. I'd just really love to know what species they all are, if possible.

Additionally, I'd also just appreciate further conversations with other Heterometrus afficionados, whether it's for ID tips, or just to wax poetic about why they're pretty great. My apologies for the rant otherwise!

I'm no expert, but from what I can gather from the revision is this.
It got cut to 8 species

Heterometrus spinifer
Heterometrus laevigatus
Heterometrus silenus
Heterometrus laoticus
Heterometrus longimanus
Heterometrus petersii
Heterometrus thorellii
Heterometrus glaucus


The Key Diagnostic Features for Differentiation are;

1. Chela Morphology;

H. spinifer: Chelae (pincers) are moderately elongated with pronounced granulation on the manus (proximal part of the chela). The fixed finger exhibits a distinct tooth near the base.

H. laevigatus: Chelae are smooth, lacking significant granulation, and the manus is globular. This species was previously confused with H. minotaurus, now synonymized under H. laevigatus.

H. silenus: Chelae are robust and rounded, with sparse granulation. The telson (sting) is uniformly black, a trait shared with H. petersii.

H. longimanus: Chelae are elongated (length-to-width ratio >2.4) and sparsely tuberculate. This contrasts with H. spinifer, which has shorter, more granulated chelae.


2. Carapace Granulation;

H. spinifer: Carapace (prosoma) has a smooth central disc with granulated margins. Granules are fewer but more pronounced compared to H. longimanus.

H. laoticus: Carapace is uniformly granulated across the entire surface, a feature shared with H. thorellii. Sexual dimorphism is evident, with males having broader carapaces.

H. glaucus: Carapace exhibits fine granulation without distinct smooth regions, differentiating it from H. silenus.


3. Telson and Metasoma;

H. petersii and H. silenus: Both possess a black telson, but H. petersii has a smoother manus and fewer pectinal teeth (15–19 vs. 18–22 in H. silenus).

H. thorellii: Metasoma (tail) segments are proportionally shorter and wider compared to H. laoticus, which has a more elongated metasoma.


4. Pectinal Tooth Count;

H. laoticus: Males have 18–22 pectinal teeth, while females have 15–18. This sexual dimorphism is less pronounced in H. spinifer.

H. longimanus: Both sexes exhibit 16–20 pectinal teeth, overlapping with H. silenus but distinguishable by chela shape.

 

[The Snark]

Frustration is the order of the day and completely understandable. Unless a person has had extensive experience with specimens and high quality photos, mistakes will be made. And even then, experts have made mistakes. Having the various species present to make side by side comparisons is still suggested.
This according the a scorp expert at the local university. It explains why AFS ID has been a musical chairs game with numerous revisions. For him, the native location where the specimen is found will greatly improve the identification issues.
He also wryly mentioned, the identification and traits of the scorp expert will also effect the identification accuracy. He used himself in comparison to a colleague in Kuala Lumpur. Example: https://wildlife.gov.my/images/stories/penerbitan/jurnal/Journal wildlife 15 January Final/Volume 28 papers/13 NOTES ON SCORPION FAUNA IN KUALA LOMPAT, KRAU WILDLIFE RESERVE, PAHANG.pdf
So now, at least, Longimanus can be differentiated from Spinifer with reasonable accuracy although some ambiguity can be found. Note the variations among Longimanus specimens. The expert can still be wrong comparing the two species by variations within species and the sex and possibly age of the specimen.

However, this species look extremely similar to the other species that was believed to occur in Penisular
Malaysia, Heterometrus spinifer but can be differentiated from H. spinifer in presence of granulations
on the carapace and the length of pedipalps which is longer in male H. longimanus (Couzijn, 1981).
Unless the species were male, to differentiate between these species can be based on the granulation
pattern on carapace. Kovaric (2004) stated that both species had smooth disc with margin granulated
prosoma however, the prosoma of H. longimanus generally more finely granulated and sometime can
had the entire prosoma granulated if compared to H. spinifer.
(can had??) Let's give that white paper another proofing please.

Also mentioned when I interviewed the expert, collected specimens on the international market may have another unusual trait. The variations in the laws between countries. Malaysian species are rare to very rare, Singapore next to non existent, Thailand much more common, Laos, Cambodia and Indonesia virtually open borders. Vietnam varies but usually uncommon.

 

[SonOfSerket]

I'm no expert, but from what I can gather from the revision is this.
It got cut to 8 species

Heterometrus spinifer
Heterometrus laevigatus
Heterometrus silenus
Heterometrus laoticus
Heterometrus longimanus
Heterometrus petersii
Heterometrus thorellii
Heterometrus glaucus


The Key Diagnostic Features for Differentiation are;

1. Chela Morphology;

H. spinifer: Chelae (pincers) are moderately elongated with pronounced granulation on the manus (proximal part of the chela). The fixed finger exhibits a distinct tooth near the base.

H. laevigatus: Chelae are smooth, lacking significant granulation, and the manus is globular. This species was previously confused with H. minotaurus, now synonymized under H. laevigatus.

H. silenus: Chelae are robust and rounded, with sparse granulation. The telson (sting) is uniformly black, a trait shared with H. petersii.

H. longimanus: Chelae are elongated (length-to-width ratio >2.4) and sparsely tuberculate. This contrasts with H. spinifer, which has shorter, more granulated chelae.


2. Carapace Granulation;

H. spinifer: Carapace (prosoma) has a smooth central disc with granulated margins. Granules are fewer but more pronounced compared to H. longimanus.

H. laoticus: Carapace is uniformly granulated across the entire surface, a feature shared with H. thorellii. Sexual dimorphism is evident, with males having broader carapaces.

H. glaucus: Carapace exhibits fine granulation without distinct smooth regions, differentiating it from H. silenus.


3. Telson and Metasoma;

H. petersii and H. silenus: Both possess a black telson, but H. petersii has a smoother manus and fewer pectinal teeth (15–19 vs. 18–22 in H. silenus).

H. thorellii: Metasoma (tail) segments are proportionally shorter and wider compared to H. laoticus, which has a more elongated metasoma.


4. Pectinal Tooth Count;

H. laoticus: Males have 18–22 pectinal teeth, while females have 15–18. This sexual dimorphism is less pronounced in H. spinifer.

H. longimanus: Both sexes exhibit 16–20 pectinal teeth, overlapping with H. silenus but distinguishable by chela shape.

Andrew,

Thank you so much. This was exceedingly helpful! Below I'll post a few pictures of my adult male. When I got my first specimen, several others on here suggested that she was H. silenus.



Based on the revision and the info you provided, I think this guy is H. laoticus. Am I close?

 

[SonOfSerket]

Frustration is the order of the day and completely understandable. Unless a person has had extensive experience with specimens and high quality photos, mistakes will be made. And even then, experts have made mistakes. Having the various species present to make side by side comparisons is still suggested.
This according the a scorp expert at the local university. It explains why AFS ID has been a musical chairs game with numerous revisions. For him, the native location where the specimen is found will greatly improve the identification issues.
He also wryly mentioned, the identification and traits of the scorp expert will also effect the identification accuracy. He used himself in comparison to a colleague in Kuala Lumpur. Example: https://wildlife.gov.my/images/stories/penerbitan/jurnal/Journal wildlife 15 January Final/Volume 28 papers/13 NOTES ON SCORPION FAUNA IN KUALA LOMPAT, KRAU WILDLIFE RESERVE, PAHANG.pdf
So now, at least, Longimanus can be differentiated from Spinifer with reasonable accuracy although some ambiguity can be found. Note the variations among Longimanus specimens. The expert can still be wrong comparing the two species by variations within species and the sex and possibly age of the specimen.

However, this species look extremely similar to the other species that was believed to occur in Penisular
Malaysia, Heterometrus spinifer but can be differentiated from H. spinifer in presence of granulations
on the carapace and the length of pedipalps which is longer in male H. longimanus (Couzijn, 1981).
Unless the species were male, to differentiate between these species can be based on the granulation
pattern on carapace. Kovaric (2004) stated that both species had smooth disc with margin granulated
prosoma however, the prosoma of H. longimanus generally more finely granulated and sometime can
had the entire prosoma granulated if compared to H. spinifer.
(can had??) Let's give that white paper another proofing please.

Also mentioned when I interviewed the expert, collected specimens on the international market may have another unusual trait. The variations in the laws between countries. Malaysian species are rare to very rare, Singapore next to non existent, Thailand much more common, Laos, Cambodia and Indonesia virtually open borders. Vietnam varies but usually uncommon.

I really appreciate that you address variations within species in your response, which as you mention, can often be a source of frustration. Even the best of dichotomous keys can't possibly account for all variation, with "odd" individuals of a given species being difficult or impossible to key, or even keyed to the wrong species. I hope to eventually get to the point of being much more familiar with the species of Heterometrus commonly seen in the pet trade. Perhaps I can use this as leverage to justify buying every AFS I can get my hands on to my partner... "it's for research!"

At any rate, at the end of the day, Heterometrus is my first and only scorpion genus to date, and I find them absolutely charming. Speaking of similarities and variation, one similarity I've noted with all my specimens is that they have all seemed to be very "spicy" behaviorally at first, but after a week or two adjusting to their new homes, they tend to mellow out quite a bit, though all of mine do seem to exhibit their own individual personality quirks, as well. I'll probably continue to collect this genus, but do hope to expand the diversity of my scorpion collection as I also further diversify my arachnid collection in general. This hobby is definitely addictive, and I really appreciate the helpfulness of others in the hobby here on the forums. Thanks again!

 

[Andrew Clayton]

Andrew,

Thank you so much. This was exceedingly helpful! Below I'll post a few pictures of my adult male. When I got my first specimen, several others on here suggested that she was H. silenus.

View attachment 494281 View attachment 494282 View attachment 494283

Based on the revision and the info you provided, I think this guy is H. laoticus. Am I close?

All the info I posted is just what I can gather from the revision.
Here is a link to the full revision,

https://bioone.org/journals/bulletin-of-the-american-museum-of-natural-history/volume-442/issue-1/0003-0090.442.1.1/Systematic-Revision-of-the-Asian-Forest-Scorpions-Heterometrinae-Simon-1879/10.1206/0003-0090.442.1.1.full?utm_source=perplexity