By behavioral and anatomical criteria, the pectinal sensory appendages of scorpions appear to be chemoreceptive organs specialized for detection of substances on substrates. These comb-like, midventral appendages contain tens of thousands of minute (< 5 microns), truncated setae, called pegs, arranged in dense, two-dimensional arrays on the ventral surface. In this study we used extracellular recording techniques to examine spontaneous and stimulated activity of sensory neurons within individual pegs. Chronic recordings lasting several days showed long-term fluctuations in spontaneous activity of sensory units in single peg sensilla, with peak activity coinciding with the animal's normal period of foraging. Several units were identified by the stereotypical waveforms of action potentials they elicit. Near-range olfactory stimulation of peg sensilla by volatile alcohols, aldehydes, ketones, esters, and carboxylic acids produced dose-dependent patterns of neural response. Contact stimulation with these chemicals, or water, or mechanical deflection of the peg tip also evoked activity in identifiable units. The peg sensilla appear to be broadly sensitive to odorants and tastants, suggesting they function similarly to the antennae of mandibulate arthropods.

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The navigation by scene familiarity hypothesis provides broad explanatory power for how bees and ants navigate from the hive to distant food sources and back. The premise is that the visual world is decomposed into pixclaled matrices of information that are stored and readdressed as the insects retrace learned routes. Innate behaviors in these insects (including learning walks/flights and path integration) provide the important goal-directed views to allow the initial retracing (i.e., the insect must learn the scene while moving toward the goal because everything looks different while moving away). Scorpion navigation may use a similar premise, with the chemical and textural features of the environment substituting for visual input. Scorpion pectines support thousands of chemo-and mechano-sensitive units called peg sensilla, each containing at least 10 energetically expensive sensory neurons. We have long wondered why pectines have so many pegs and associated neurons. Many sand scorpions emerge onto the surface from their home burrows at night to pursue insect prey and somehow find their way back to their burrows. Based on the measured resolution of peg sensilla, we have calculated that sufficient information exists in sand's texture to enable scorpions to retrace previously experienced paths with little to no chance of confusion. Preliminary evidence of learning walks and path integration in scorpions is also congruent with the navigation by chcmo-textura! familiarity hypothesis.

1992: Evidence of chemical signaling in the sand scorpion, Prtruroctonus mesaensis (Scorpionida: Vaejovida). Ethology 91, 59-69. AbstractThis study presents evidence of intraspecific chemical communication in scorpions. The subject of our investigation was the nocturnal sand scorpion, Paruroctonus mesaensis. During the mating season, mature males show a sex-specific wandering behavior ostensibly directed at locating conspecific females that remain in the vicinity of their home burrows. Searching behavior was stimulated in the laboratory by releasing males onto substrates that had previously been occupied by females. Receptive males exhibited changes in locomotory behavior that favored occupation of the femaleexposed area, Males occasionally displayed a precourtship behavior, called juddering, indicating the presence of a pheromone on the substrate. Juddering, and two newly described behavior patterns, tailwagging and pedipalp-reaching, were also induced by solvent extracts of female cuticle. Most behavioral responses began vigorously within the first few s of stimulus contact and gradually adapted within 10 min. The potential importance of specialized sensory appendages, the pectines, for mediating chemosensitivity is discussed. These results are consistent with the hypothesis that mate identification and localization in sand scorpions are mediated in part by a contact sex pheromone.

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Humans have long marveled at the ability of animals to navigate swiftly, accurately, and across long distances. Many mechanisms have been proposed for how animals acquire, store, and retrace learned routes, yet many of these hypotheses appear incongruent with behavioral observations and the animals’ neural constraints. The “Navigation by Scene Familiarity Hypothesis” proposed originally for insect navigation offers an elegantly simple solution for retracing previously experienced routes without the need for complex neural architectures and memory retrieval mechanisms. This hypothesis proposes that an animal can return to a target location by simply moving toward the most familiar scene at any given point. Proof of concept simulations have used computer-generated ant’s-eye views of the world, but here we test the ability of scene familiarity algorithms to navigate training routes across satellite images extracted from Google Maps. We find that Google satellite images are so rich in visual information that familiarity algorithms can be used to retrace even tortuous routes with low-resolution sensors. We discuss the implications of these findings not only for animal navigation but also for the potential development of visual augmentation systems and robot guidance algorithms.

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Chemical signaling promotes mate location throughout numerous animal taxa. In this study we investigated the possibility that striped scorpions, Centruroides vittatus, use chemical signaling in the form of odor plumes or substrate-borne deposits as communication channels. A Y-shaped arena was constructed to test scorpions' use of airborne chemical cues in the detection of potential mates. A second, circular behavioral choice chamber was used to test male scorpions' responses to female deposits by direct substrate contact. Male scorpions showed no tendency to move toward the female in tests of airborne chemical transmission but they did demonstrate behavior associated with chemical detection when exposed to substrate-borne feminine deposits. Our experiments do not provide evidence that male C. vittatus use aerial pheromones to locate female scorpions but that they are highly sensitive to direct contact of substrate-borne chemical deposits.