A desert scorpion can smell its enemies

Avoid being eaten or killed is one of the fundamental drives in all animals and an impressive range of anti-predator tactics have been described. Scorpions have their powerful claws and a venomous sting, but other tools are also available.

Zia Nisani and co-workers have now published a very interesting article showing that the desert scorpion Paruroctonus marksi (Haradon, 1984) (Vaejovidae) can actually smell the proximity of a potential predator (in this case the much larger scorpion Hadrurus arizonensis (Ewing, 1928) (Caraboctonidae)) and then avoid approaching it. This is the first evidence of airborne chemoreception as an anti-predator strategy in scorpions.

One of the experiments in this study point to a special constellation array of sensilla (or a yet unidentified structure) on the pedipalps as the "sense organ" used to detect the odors of predators.

Abstract:
Chemically induced predator avoidance behaviors exist in many arthropods. In this paper, we examined the behavioral responses of the desert scorpion, Paruroctonus marksi (Haradon, 1984), to airborne chemical cues from a natural predator, the larger scorpion Hadrurus arizonensis (Ewing, 1928). We used a Y-shaped, dual-choice olfactometer to test for avoidance behavior in the presence of a known predator, H. arizonensis. Prior to this study there has been little research done on chemically induced predator avoidance behaviors in scorpions. The results of this study suggest that P. marksi is capable of detecting a predator’s airborne cues, though the nature and identity of these cues remain unknown, and it appears that the constellation array of the fixed finger does function in detecting these cues. We also discuss the importance of adaptive predator avoidance behaviors.

Reference:
Nisani Z, Honaker A, Jenne V, Loya F, Moon H. Evidence of airborne chemoreception in the scorpion Paruroctonus marksi (Scorpiones: Vaejovidae). Journal of Arachnology. 2018;46:40-4. [Open Access]

Thanks to Matt Simon for informing me about this article!