It is summer now and the rains have arrived in earnest. This has resulted in the brown, parched earth to now be covered in lush, green grass and vegetation. The trees are also in full leaf and there are many forbs flowering. The insects are now taking advantage of the new greenery, the moisture and the warmer night temperatures. Along with the insects that have come out there are also those creatures and “goggas” that feed upon them. Among these predators are those creatures that are known as scorpions. Summer is the time that the scorpions are active.
Scorpions are invertebrates and are members of the class Arachnida. They are closely related to spiders, solifuges, mites, and ticks. They are easily recognizable by their three body parts (the prosoma or “head”, the mesosoma or the “body” and the metasoma or the “tail”), their 8 legs, their pincers/pedipalps and their often up-curved tail with the “stinger” or telson on the end.
There are round about 1 500 species of scorpions in the world and at least 130 species occur in southern Africa. Scorpions are found on all the continents of the world with the exception of Antarctica. Scorpions are among the earliest forms of land animals and fossils of extinct scorpions have been found in rocks dated before dinosaurs existed. The oldest scorpion-like fossils are reported to be at least 425 million years old and the oldest true, terrestrial scorpion fossils are at least 350 million years old.
Scorpions are predominantly nocturnal (active at night) and fossorial (animals that are adapted to living underground) and they tend to find shelter during the day in the relative coolness of underground holes, under the bark of trees or underneath rocks. They come out at night to hunt and feed (more often on moonless nights when they can evade other nocturnal predators e.g. birds, centipedes, lizards, mice, genets, honey badgers etc.). We sometimes see them walking on and across the roads on windy nights during summer. Scorpions fulfil an important role in the ecosystem as they not only feed upon other invertebrates, but are also an important source of protein for various other creatures.
They are generally secretive creatures and very few of our guests even see them. It is estimated that scorpions spend up to 95 percent of time inactive and, due to this inert lifestyle some species of scorpions are able to survive without food for more than a year. Scorpions are opportunistic predators of small arthropods, although the larger kinds have been known to kill small lizards and mice. Scorpions can consume huge amounts of food at one sitting.
Depending on the species some scorpions kill their prey with their pincers, while others use their stings to subdue or kill their prey. The venom not only acts as an immobilizing agent, but actually begins the digestive process. They feed by chewing off pieces of their prey using their mouthparts or chelicerae. Their saliva aids the digestive process by liquefying the food items and any solid remains (e.g. hairs, hard exoskeletons etc.) are then sieved out by hair-like structures (setae) in the oral cavity and regurgitated.
Most scorpions reproduce sexually. Males tend to be more active than females and when the males locate the females (who often remain most of their lives in or nearby their burrows) they need to identify each other using a mixture of pheromones and vibrational communication. Once they have satisfied the other that they are of the opposite sex and of the correct species, mating can commence. The mating ritual often involves taking part in a very complex dance with each other. This dance is known as the “promenade à deux”, and can take from few minutes to hours. The dance starts with the male grasping the female’s pincers with his own and sometimes the pair even interlock their mouthparts. In some species the male may even sting the female, which is thought to calm the female down and make her more receptive to his amorous advances. In the “promenade à deux” the male leads the female around searching for a suitable place to deposit his spermatophore (a capsule containing the sperm). When the male has identified a suitable location, he deposits the spermatophore and then guides the female over it. This allows the spermatophore to enter her genital opening.
The gestation period of scorpions varies from species to species and ranges from only a few months to as long as 18 months (which is exceptionally long for an invertebrate). Most scorpions give birth to live young (although in some species the young develop inside eggs within the female and hatch before being “born”). Scorpion litters vary in number greatly and may be affected not only by species but also by environmental factors. In South Africa litter size may vary from 8 to over 30 individuals. The young generally resemble their parents. These young scorplings will live on the mother’s back for the first several weeks of life. She will care for them until they go through the first moulting period.
Growth is accomplished by periodic shedding of the exoskeleton (ecdysis). A scorpion’s developmental progress is measured in instars (how many moults it has undergone). Scorpions typically require between five and seven moults to reach maturity. When a moulting scorpion emerges from its old skin the new exoskeleton is soft, making the scorpion highly vulnerable to attack.
The average lifespan for a scorpion in the wild is from two to ten years. However, some of them have been known to live in captivity for up to 25 years.
The exoskeletons of scorpions glow a vibrant blue-green when exposed to certain wavelengths of ultraviolet light such as that produced by a black light. This is very handy when looking for scorpions at night as they are very easy to see when an ultra-violet light is shone on them. It is not fully understood as to what the reason is that scorpions should have this eerie characteristic and the function it serves.
All known scorpion species possess venom and use it primarily to kill or paralyze their prey so that it can be eaten, or in self-defence. The venom is a mixture of compounds (neurotoxins, enzyme inhibitors, etc.) each not only causing a different effect but possibly also targeting a specific animal. There are very few scorpions in southern Africa that are considered to be dangerous to humans. Most envenomations, by scorpions, just cause local pain (much like a bee-sting), although the venom from the thick-tailed species can be serious, causing extreme pain and even possibly affecting the nervous system to the degree that it alters breathing, circulation and muscular co-ordination. There have been very few human deaths that have been recorded from scorpion stings in southern Africa.
Southern African scorpions fall into four main families. These are Bothuridae (these are very rare and do not occur in our area), Buthidae (these include the thick-tailed scorpions and the bark scorpions), Ischneuridae (some burrowing / creeping scorpions and some rock scorpions) and Scorpionidae (burrowing scorpions). Of these only the scorpions from the family Buthidae (particularly the Parabuthus species) are considered dangerous. Some of the Parabuthus species are even known to flick or spray their venom, which could potentially end up in a person’s eyes if looking at it too closely!
A general rule regarding the potential danger of scorpions is: Scorpions with weak or small pincers and a thick tail use their venom to subdue prey and are therefore more likely to be dangerous to humans, whereas scorpions with large pincers and a thin tail tend to use their pincers to overpower prey and their venom is usually weak.
In other words:
Small pincers + thick tail = serious
Big pincers + thin tail = not serious
In southern Africa the four most dangerous scorpions all belong to the genus Parabuthus (Thick-tailed Scorpions). These are Parabuthus granulatus, P. transvaalicus, P. capensis and P. mossambicensis. Of these four scorpion species P. transvaalicus and P. mossambicensis can both be found in the Lebombo area. Fortunately, they do not generally enter rooms and our pathways are raised on wooden boardwalks and therefore the chance of standing on one is minimal.
When in the bush it is important to do the following in order to avoid being stung by scorpions:
Always use a torch at night
Wear closed shoes at night
Be careful when turning over rocks or picking up logs and firewood (most scorpion stings in South Africa are from bark scorpions).
Shake out your shoes before putting them on.
Look into your bedding before climbing into your bed.
Shake out clothing and towels before using them.
Avoid sleeping directly on the ground when camping.
Do not leave clothing lying in a heap on the floor or on the ground.
Images: Lilac-breasted roller feeding on a scorpion (main image by Barry Peiser), Uroplectes carinatus, Cheloctonus jonesii, Parabuthus transvaalicus, Opistacanthus leavipes and the Parabuthus mossambicensis.