The emperor scorpion, Pandinus imperator (C. L. Koch, 1841) is a member of the family Scorpionidae Latreille, 1802 and is distributed throughout many West African nations. It is the largest and most impressive scorpion species in the world; capable of attaining adult sizes of 5–7 inches, with exceptionally large specimens growing to 8-inches or slightly more in total length. Typical specimens are glossy black but may also be dark brown or dark green in overall coloration. All emperors possess large, powerful, well-developed, profusely granulate, spatulate chelae (“claws”) and a red to reddish-brown telson (“stinger”) as adults. Due to its size, menacing appearance, generally inoffensive nature and common availability the mighty emperor scorpion is the most commonly kept scorpion species among enthusiasts of all ages and skill levels.
The emperor is an inhabitant of hot, humid tropical rain forest and savanna regions throughout Benin, Congo, Cote d’Ivoire, Democratic Republic of Congo, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Sierra Leone and Togo. The majority of wild-caught specimens sold in the pet-trade originate from Ghana and Togo. Emperors have been reported to occupy hollow galleys within decomposing logs, under ground cover, in burrows, under and within the roots of trees, within termite mounds and foraging amidst leaf-litter and ground cover on moist forest floors. The below listed climatic data for Togo is based on a 12-month period and is representative of the climatic conditions in the majority of West African nations:
Average temperature: 85°F (max.); 75°F (min.)
Average humidity: 96% (am); 68% (pm)
Rainy seasons: April–July (North); March–July and October–November (South).
Annual precipitation: 35” (South); 45” (North).
Climatic regions: Hot and humid (South); Semi-arid (North).
While its primary surface activity period is during the night, emperors have been observed actively foraging during the day and low-light (crepuscular) periods. The decreased intensity and amount of sunlight in dense rain forested areas probably accounts for the reports of diurnal activity in emperor scorpions. Like all scorpions, emperors lie in ambush at the entrance of occupied retreats during the night waiting for random prey to move close enough for capture but they will also forage away from burrows and retreats when hungry or during times when prey is scarce. While emperors do possess venom, specimens greater than 3” in length generally rely on the crushing power of their large chelae to capture and immobilize prey and for self-defense. When annoyed, provoked, or startled the majority of emperors will use their powerful chelae to deliver one or two painful grasping attacks. However, many adult and sub-adult males and a smaller number of adult females may also “sting” during self-defense. The venom of emperor scorpions is not considered medically significant to humans and a typical envenomation (“sting”) produces only brief localized pain, redness, minor swelling, and short-term discomfort.
Contrary to many reports of “docility” among emperor scorpions, these scorpions can exhibit a broad-range of defense-related behaviors ranging from being inoffensive and highly-tolerant of touch and handling to completely intolerant of touch and handling and unpredictably, spontaneously reactive in defense. Defensive reactions also vary between the sexes. Females of all developmental stages tend to be more tolerant of physical interactions than males. Males from the fifth-instar onward generally rely more on venom use during defense than females. The tolerance of individual specimens to physical interactions also influences the degree and rate of defensive reactions. Lastly, temperature within the enclosure also influences defensive reactions with specimens maintained at higher temperatures generally less tolerant and more reactive to physical contact.
Despite an abundance of emperor-related information available in books, articles and online sites, the information regarding the proper rearing of early-instar specimens is often incomplete, inaccurate and/or contradictory in nature. The information contained within the present article is not intended to represent the exclusive method of rearing young emperors. It is offered to provide a simple, straightforward and practical alternative method for keeping young emperors in captivity.
If you suspect that your emperor is gravid and she’s being maintained in a group enclosure, she will need to be separated from the group and re-housed in an individual enclosure under optimum environmental conditions in order to reduce stress and insure a short gestation period.
A standard 5.5 gallon glass aquarium makes for a spacious maternity enclosure for any size emperor. Clean the enclosure with warm water and a small amount of bleach, rinse thoroughly and allow to dry. Once the enclosure is dry, add a 5”–6” inch layer of moist, moderately compressed substrate. Regardless of the type of substrate medium used (avoid sand, sand-based mediums and cat litter) within the enclosure, an equal amount of lightweight sphagnum peat should be added to decrease the overall weight of the substrate and to slow the decomposition rate of uneaten prey. The majority of commercially available sphagnum peat is acidic in nature with pH values in the range of 4.5–5.5. The acidic nature of sphagnum peat retards the decomposition of prey remains thereby; indirectly decreasing the chance of a large scale mite invasion due to an abundant source of nutrition within the maternity enclosure.
The whitish, slow-moving globular mites commonly observed in the enclosures of captive invertebrates that require warm and humid environments are members of the acarid genus Sancassania Oudemans (Astigmata) and are common saprophages feeding on necrotic tissues of decaying animal and plant material. While no current evidence implicates these mites in predatory attacks upon captive invertebrates, they commonly infest and occupy moist regions of the chelicerae and pre-oral cavity and may even enter the moist book lungs from under the protective book lung plates, possibly causing indirect harm by elevating stress levels and impairing the ability of the scorpion to feed. While many tend to believe that typical mite infestations are comprised of two different species, the fact is that the larger whitish colored mites are the adults and the smaller pinkish to light brown specimens often found on the integument of captive scorpions are the phoretic deutonymphs. There is no “one time” effective means of eradicating mites aside from a complete enclosure change. The most effective means of controlling mite population numbers is the prompt removal of all dead or uneaten prey remains as soon as the scorpion is finished feeding.
Sancassanid mites appear to be phorets on common house crickets (A. domesticus) acting as host transporteurs (unpublished data). Many Sancassania species are recognized as phoretics (commensals) upon members of several invertebrate taxa (Coleoptera, Hymenoptera, Orthoptera); the deutonymphs of the above Sancassania sp., infest and remain on host crickets until the crickets die and subsequent stages utilize the necrotic tissue of the decaying crickets as a source of food (necromeny) (unpublished data). When mite-infested crickets are introduced into the enclosures of captive emperors, mites disperse and mate while; others invade the scorpion as a new transporteur. Scorpions and their feeding method and the discarding of indigestible remains of masticated prey provide a ready source of food for the polyphagous mites. Emperors and the above sancassanid mites require the same environmental conditions to grow, reproduce and thrive, and thorough, routine enclosure maintenance is a must in order to avoid large scale mite outbreaks.
The gestation period of emperors is variable and can range from 7–14 months depending on environmental conditions (humidity and temperature), frequency and quantity of feedings and on the individual specimen. The gestation period for the majority of emperors is approximately 300–340 days. Once the embryos reach an advanced stage of development the gestation period ends and the last stage of pre-parturition begins. During the late pre-parturition stage, emperor females may be reluctant to feed and may exhibit increased burrowing activities. Increased burrow excavation is typically a behavioral indicator that a gravid female is increasing the depth of burrows or chambers beneath surface structure in preparation for birth. It is also during the late stages of pre-parturition that gravid females enter and remain secluded within their burrows or retreats until the young are born and may remain in their retreats until the young disperse and become free-living. However, the majority of maternal females will resume surface activities within a week of giving birth.
Once the female emperor secludes herself within a burrow or retreat, the actual birth occurs within 1–10 days. Births generally last from 3–12 hours, with the majority of females producing 6–32 offspring per litter. In captivity, litter size ranges from 8–20 young. After emergence from the maternal female, the white, bloated first-instar scorpions exhibit only limited mobility and move cumbersomely upon the substrate. After a short period of rest, the young emperors begin the ascent from the substrate surface up the walking legs of the maternal females. Moving from the walking legs, the young begin to randomly aggregate in increasing numbers, several layers deep upon the dorsum (“back”) of the female where they’ll spend the next 14–18 days being transported by the maternal female. During the first-instar stage, the young scorpions do not feed but rely on stored nutrients within their bodies to provide sustenance during this period, which is an external continuance of the embryonic stage and is often referred to as the post-embryonic stage. First-instar emperors share few similarities with the large adults: the aculeus (“stinger”) is blunt and cannot inject venom for prey-capture or defense; the ungues are blunt and serve as suction pads instead of well-developed claws; the chelae are without dentition and the mouth parts consist of a proboscis-like projection. During the first-instar stage, the young emperors cannot feed.
While there have been many hypotheses published that attempt to explain why female scorpions transport their young on their dorsa and the adaptive significance of the transport system and the mother-young relationship during the first-instar, one of the most significant hypotheses that attempts to explain this phenomenon is that the young scorpions cannot control the amount of water lost from their bodies due to the lack of a water-proof integument and if enough water is lost, the young scorpions will desiccate and perish. During continuous or periodic contact between mother and young, the maternal female provides water through her integument that is absorbed by the young scorpions thereby, continuously replenishing water lost through the integument; preventing the young scorpions from becoming desiccated.
However, while the above hypothesis presents the most evolutionarily plausible explanation for this system of transportation, another hypothesis that attempts to explain the adaptive significance of the dorsal transport system of female scorpions is that with the entire litter upon her dorsum, a female scorpion can continuously select optimal environmental conditions for her young by moving within and between microhabitats within a larger, more generalized habitat thereby; allowing the maternal female to select conditions conducive to the rapid and optimum growth of her litter. The scorpion transport system and the ability to move in order to select optimum conditions for the young would certainly benefit emperors that inhabit forest edges and savanna systems affected by drought and adverse seasonal climatic conditions. However, providing a balance between water loss and gain in the first-instar young is still the primary factor of both hypotheses.
With internal nutrient stores near depletion, the young emperors begin to exhibit increased activity and movement in preparation for their first molt. The first molt signifies a great change in the life of each young scorpion. Unlike the first-instar stage in which, the young scorpions continue the embryonic stage in an external environment; the first molt transfers the undeveloped embryos into smaller, fully functional representations of the adult scorpions.
During the molting process, the integument separates along the anterior and lateral edges of the prosoma in preparation for the emergence of the young scorpion from its former exoskeleton. During alternating periods of active movement and rest, the young scorpions move slowly forward from out of their former “skins” and after a varying period of time (up to several hours per specimen), the young scorpions fully emerge from their former exoskeletons. Weakened and largely inactive and immobile, the young scorpions rest upon the substrate for a few hours to a day or more. During the post-molt stage, the newly-formed cuticle will harden and darken in coloration and the young scorpions will disperse from the dorsa of the maternal females (3 to 5 days post-molt) and begin to actively explore the confines of the maternal female’s burrow and capable of using venom and feeding, ascend the burrow shaft to move to the entrance of the burrow or out into the open in search of their first meal. At this stage of development, the young emperors are small replicas of their parents and may remain within the burrows of maternal females until adulthood or leave the home burrows and strike out on their own. Over the course of 1–2 years and 6–7 molts, the young emperors will attain sexual maturity (adulthood) and will be capable of mating and producing their own young in 1–1.5 years. It is also at this stage that the keeper will need to decide whether to leave the young with the maternal female, separate the young into several smaller groups, or house them in individual containers. As emperors exhibit sub-social behavior and do well in either group or individual set-ups, the final choice of preferred housing is left to the individual keeper.
However, as sub-social behavior is rarely encountered in scorpions, with the majority of species living solitary lifestyles except for brief interactions during birth, mating, seasonal aggregation, random encounters and predation, the keeper is encouraged to allow at least a small number of offspring to remain with the maternal female and siblings or to establish several small groups of siblings in order to take complete advantage of this unique and fascinating opportunity to observe the interactions between the members within a sub-social group.
However, sub-sociality does not exclude infrequent acts of economic (opportunistic) cannibalism by maternal females, siblings and unrelated group members and it does not exclude antagonistic behaviors among group members. Hungry females may feed on 1 to 3 offspring in order to regain valuable energy lost or expended during the pre-parturition or transport stages when many females refuse to feed. It may also occur during the actual birth process. Maternal females will also cannibalize offspring that are born in various stages of incomplete development, still born or that suffer from deformities or anomalies. Cannibalistic behavior during the birth process is especially common among young female emperors delivering their first litter. Although, economic cannibalism is rarely reported among emperors, it has been observed and typically occurs during the molt or early post-molt stage when a molting or freshly-molted emperor is weak, defenseless and vulnerable to attack from a typically larger group member.
For those keepers not interested in observing sub-social behavior or that prefer to isolate the young in separate containers, housing and rearing young emperors is a simple and undemanding task. Young emperors, like all animals in general, have several basic needs that need to be satisfied in captivity: frequent supply of food and drinking water, protective shelter and an environment conducive to the health and well being of the scorpions throughout all stages of the developmental period. Meeting the requirements of these four basic needs will allow the young emperors to grow and thrive to adulthood and beyond.
Even at birth, young emperors are larger than the young of most other scorpion species offered in the pet-trade. After dispersal from the maternal females, the second-instars can be transferred to individual 8” x 6” x 4” plastic food storage containers with a moist 3” layer of compressed substrate and a small curved piece of cork bark for shelter. Emperors can be maintained in the recommended containers until they complete the third molt to the fourth-instar and will then need to be transferred to larger enclosures. To maintain high levels of moisture within the small enclosures, restrict airflow by providing 3–4 small (1/8”) ventilation holes through the upper surfaces on opposing walls. Just prior to introducing a young scorpion to its new enclosure, saturate 1/3 of the substrate with room temperature distilled water. This will provide an immediate increase of humidity within the enclosure.
During the early stages of development, emperors should be maintained under high temperature and high humidity levels for optimum growth and development. While adult and sub-adult emperors tend to be hardy and able to live under a broad-range of environmental conditions, younger specimens do best when kept under hot and humid conditions that replicate the natural environments of tropical rain forests. Temperatures should be maintained in the range of 85° to 90°F during the day and 77° to 79°F at night. The substrate should always be kept moist to the touch and humidity levels in the range of 80 to 90%. Once the developing emperors reach the fourth-instar, humidity levels can be decreased and need not exceed 85%.
Emperor scorpions are generalist predators that will readily feed upon any invertebrate or small vertebrate prey that they can capture and subdue with their large powerful chelae. In the wild, the diet of emperors is primarily composed of invertebrate prey, with the acquisition of vertebrate prey presenting a challenge to the large and slow-moving emperors. Unlike adult and sub-adult emperors, the young readily utilize their venom to subdue prey. As the young molt and grow the use of venom to subdue prey will decrease until rarely used by emperors of 3” or more in length. Young emperors vary in their feeding rates but most will accept a single 3/8”–1/2” common house cricket (Acheta domesticus L.) or comparable type of prey (e.g. roaches), 2–3 times per week. Offer young emperors prey at least twice weekly in order to promote continuous rates of growth. Always provide a standing source of drinking water to the young scorpions. A plastic bottle cap from a two-liter soda bottle, kept filled with distilled water works well in smaller containers. While it is true that emperors, like other scorpions, intake most of their liquid requirements from consumed prey, most will readily drink when water is offered. Emperors will also enter and submerge themselves in standing sources of water for periods up to 20-minutes. While this is considered a common behavior in older specimens, the size of the container used to supply water should be small enough to prohibit a young emperor from entering, submerging and possibly drowning. Unlike larger specimens, young emperors may not possess the ability to exit standing sources of water.
Spacious housing, optimal environmental conditions and frequent feedings all contribute to promote a fast to moderately-fast rate of growth that may allow a young emperor to attain adulthood within its first year. Few aspects of scorpiculture are as rewarding as rearing a scorpion from birth to adulthood and have it reward its keeper by mating and producing young of its own.
DEVELOPMENT AND CARE OF EARLY-INSTAR PANDINUS IMPERATOR by LUCIAN K. ROSS
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