Differences between Scorpions (Genera Heterometrus and Pandinus)

 

Differences between Scorpions (Genera Heterometrus and Pandinus)

Arachno-hobby has been increasing for the past few decades. More and more people keep scorpions as pets. Unfortunately, owing to the difficulties involved in the identification of the most popular genera (Heterometrus and Pandinus), scorpions are often advertised under false or erroneous names.

There is a popular opinion that the difference between genus Heterometrus and genus Pandinus can be told apart by the color of the stinger and the texture of their pincers.

Well, this is not exactly so. In reality, it is way more complicated than that.

In this article, I am going to describe in depth how we can differentiate the genera Heterometrus and Pandinus based on scientific literature.

Why is it important to know the difference between species (genera)?

Understanding what different scorpion species can bring to the table can help you to make an educated decision regarding your purchase.

When you are buying a pet scorpion, you need to know what classification it belongs to. In the future, it will allow you to research more about this particular species.

For example, there are many pet scorpion species and each of them is native to a different natural environment. Therefore, different living conditions may be required in a captive setting.

Note: Order Scorpionida includes about 1,500 species and 155 genera. Scorpions are widely distributed around the world and can be found in forests, savannahs, deserts, mountains, and even in residential areas.

Also, it can also cause problems if different species are kept together or affect the breeding results.

In addition, it is a well-known fact that some scorpion species may be more aggressive and/or more venomous. Scorpions are fascinating creatures to watch and have lots of personalities. Nonetheless, they are not completely safe, especially, for those who are allergic to their venom.

That is why it is very important to know more about the species we keep.

Differences between Heterometrus longimanus, Heterometrus petersii, and Heterometrus spinifer

Heterometrus longimanus, Heterometrus petersii, Heterometrus spinifer, and Pandinus Imperator are the most popular species in the hobby.

Nonetheless, despite their popularity as pets, these species are often mislabeled and misidentified and sold in the hobby under the same name as the Asian forest scorpion or even as the Emperor scorpion.

These four species can be easily confused with each other because they are quite similar in color and appearance, especially, when they are young.

Even scientists say that distinguishing some of these valid taxa on solitary, lest immature, is very difficult and often impossible. The species can be reliably identified only on adult males.

So, be careful and watch for labeling in pet stores!

Differences between Heterometrus longimanus, Heterometrus petersii, and Heterometrus spinifer
pictures of the Genus Heterometrus (sourse) and Pandinus Imperator

Many hobbyists believe that we can notice the difference between the genus Heterometrus and genus Pandinus by checking their:

  • Claws texture (smooth in Heterometrus and pebbly in Pandinus).
  • Stinger (dark in Heterometrus and brown/light in Pandinus).

Well, it is true… but not always! A taxonomic review of these species is significantly more complex.

Related article:

  Heterometrus spinifer
(Malaysian black scorpion)
Heterometrus petersii
(Malaysian forest scorpion)
Heterometrus longimanus
(Long-clawed rainforest scorpion)
Pandinus Imperator
(Emperor scorpion)
Base color
(body and stinger)
uniformly black, only manus and telson may be reddish brown from greenish-black to uniformly black, only manus and telson may be reddish brown uniformly black, only manus and telson may be reddish brown entirely reddish or dark brown or black with pale telson
Average size of Adults

 

3.9 – 5.3 in inches (or 100–135 mm) in long 3.5 – 4.9 inches (or 90–125 mm) in long. 3.5 – 5.5 inches (or 90–140 mm) in long 6.7 – 7.8 inches (or 170–200 mm) in length
Claws texture smooth, with smooth carinae forming irregular reticulation. much of manus smooth, with smooth carinae mainly on margins. much of manus smooth, sparsely tuberculate. chela surface reticulate to coarsely granular
Claws size slightly lobiform, its adult length to width ratio 2.4–2.6 in both sexes. male has more pronounced tooth on movable fingers of pedipalp. Chela rounded, its length to width ratio 2–2.4 in both sexes. male with chela, femur and patella of pedipalp narrower and longer than in female.

Chela not lobiform in male, slightly lobiform in female, its length to width ratio 3.3–4.4 in male, ca. 2.4. in female

very wide and round, dorsally with rounded granules, rarely conical or pointed
Patella of pedipalp

 

with pronounced internal tubercle. without pronounced internal tubercle. with pronounced internal tubercle.  
Pectinal teeth number 15–19 15–19 12–18 16 
Carapace texture with disc smooth and margins granulate with disc smooth and margins granulate. usually with disc smooth and margins granulate, but sometimes entire surface granulate. surfaces of  carapacefinely to coarsely granular laterally, smooth to coarsely granular in interocular region, and smooth posteromedially
Telson hirsute elongate, vesicle longer than aculeus elongate, vesicle longer than aculeus elongate, vesicle as long as or longer than aculeus. Telson with only a few short setae
Behavior defensive defensive defensive most docile

Main Difference between Genera Heterometrus and Pandinus

According to the study, the genus Heterometrus can be separated from the genus Pandinus by the following characteristics:

  • pedipalps orthobothriotaxic, with 26 trichobothria (patella with 13 trichobothria in e series and 3 trichobothria in v series; chela with 4 trichobothria in V series and 2 trichobothria in i series);
  • granular tubercles of ‘rasp’ and stridulatory setae (scaphotrix) of ‘scraper’ situated on coxae of first leg and pedipalp, respectively.

Note: Trichobothria (singular trichobothrium) are elongate setae (“hairs”) present in scorpions.

As we can see, it is not that easy to see the differences between the most popular scorpion species with your bare eyes. In some cases, the morphological differences are so small that you would need the help of special literature and a microscope to see them.

In Conclusion

To provide proper care for our pets, we need to know what species this is to understand its requirements and be prepared for this demand.

Thus, the question of the visual difference between different scorpion species (such as Heterometrus longimanus, Heterometrus petersii, Heterometrus spinifer, and Pandinus Imperator) arises all the time.

There have seen countless posts on forums and Facebook groups where people have had problems with that.

Contrary to popular belief, we cannot simply rely on claw texture and stinger coloration to solve this problem. Unfortunately, the problem is much more complex. So, even professional taxonomists acknowledge this fact.

References:

  1. Kovařík, František. “A review of the genus Heterometrus Ehrenberg, 1828, with descriptions of seven new species (Scorpiones, Scorpionidae).” Euscorpius 2004, no. 15 (2004): 1-60.
  2. Holstein, Joachim, Ingo Wendt, and Andrea Rossi. “The Emperor is back! Rediscovery and redescription of the holotype of Pandinus imperator (Scorpiones: Scorpionidae).” Arachnologische Mitteilungen 54 (2017): 44-47.
  3. Systematics and biogeography of the family Scorpionidae (Chelicerata : Scorpiones), with a discussion on phylogenetic methods. Invertebrate Systematics, 2003

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