Tropical Scorpions: What You Don’t See Can Hurt You
By Tara A. Spears
Most people dislike spiders. Most people really dislike and fear scorpions- with the very thought of having these insidious critters in your home has one running for poisons to kill it. While usually March through June (when nighttime temperatures are above 70 F/ 21C) are peak scorpion activity months in the Riviera Nayarit, perhaps due to the mild, dry winter I have seen scorpions every day this last week. Interestingly, of the 221 species of scorpions in Mexico, only eight are poisonous to humans. That being said, according to the scientists at the Universidad Autonoma de Guadalajara there were 53,840 cases of scorpion stings in Mexico (2008) with the most stings occuring in coastal Jalisco and Nayarit. This is logical since scorpions thrive in tropical regions, and since there is a lot of natural habitat in these states coupled with pockets of dense human populations along the coast, it is obvious that stings will occur. Yet when armed with a little knowledge of scorpions and some prevention techniques it is possible to safely co-exist with this shy yet nasty beast.
Not a Spider
Scorpions are arthropods — a relative of insects, spiders and crustaceans — and have changed little in the last 400 million years or so. Scorpions prefer to live in very dry climates. Despite this, they are very sensitive to the loss of moisture from their body. They must drink water and they hide during the day in shady burrows. I realized that the reason I was seeing so many on the patio at night was that they were coming out from the garden rock edgings to drink from the dog’s water dish- yikes! Now I remove the water from the pet dishes- inside and on the patio- each evening and refill the bowls in the morning.
Female scorpions carry their eggs inside their bodies. When the young leave the female’s body, they climb onto the mother’s back. They stay on the mother’s back until they have gone through their first molt. After that, they climb down and scatter. Small scorpions look exactly like mini-adult scorpions; I’ve seen them walking around smaller than my smallest fingernail. As they age, they shed their exoskeletons. A young scorpion’s progress is measured by the molting stage since it requires five to seven molts to reach maturity. The scorpion’s exoskeleton is tough, making it difficult to kill it by crushing- it takes several stomps to annihilate one.
I find the fact that a single scorpion’s life span ranges between four to fifteen years to be depressing. This fact indicates that there is just no way to permanently eliminate them from a tropical yard. Scorpions prefer to live within the temperatures of 18°C to 45°C. They find shelter during the day in underground holes or undersides of rocks, inside shoes, or any dark crevice inside or out of a house. I see them every time I lift a flower pot in my yard- it’s amazing how small a space scorpions can fit through. Several times I have had them in mops that were set outside to dry after using. I know to be vigilant as I work around the garden.
Scorpions become nocturnal when they are old enough to hunt and feed. They invade predators’ homes such as birds, centipedes, lizards, mice, opossums, and rats. When hunting for a prey, they use their chelae, or pincers, to either crush or inject their victims with neurotoxic venom, which actually paralyzes or kills their prey. The venom is carried in a gland on the back of the tail, and when on the attack, a scorpion can flick its stinger over its head with lightning speed. The venom itself contains a complex mix of toxins that affect the nervous system (neurotoxins). Scorpions also use small, claw-like structures that protrude from their mouth for eating. Scorpions can only chew their food in a liquid form and will dispose any solid matter before ingestion. Scorpions also eat a variety of insects, spiders, other scorpions, and lizards, which is why they are useful in the environment. While scorpions must have water to drink, they can survive for months without food- but since there is no shortage of geckos, ants, and spiders, the local scorpions are quite robust.
While I, and most people, feel scorpions are a menace, scientists believe that some scorpion venoms can actually be beneficial to humans. Scientists recently found one type that can be used to treat brain cancer. When administered properly, certain chemicals in the scorpion venom kill cancer cells, but leave a person’s healthy cells unharmed, according to researcher Lorenzo Prendini with the America Museum of Natural History. Prendini says “The search for medicinal uses of scorpion venom has just begun. I have no doubt that as we learn more about scorpion venoms we will discover more uses.”
These arachnids generally run from danger and only use their venom when they feel trapped or cornered. When people find a scorpion under rocks or other places, the scorpion will often try its best to get away as quickly as possible; this means that they will only use their venom if a person tries to touch them. In general, scorpions are not aggressive. They do not hunt for prey; they wait for it. Scorpions are nocturnal creatures; they hunt during the night and hide in crevices and burrows during the day to avoid the light. Thus, accidental human stinging occurs when scorpions are touched while in their hiding places, with most of the stings occurring on the hands and feet.
Scorpion Stings and Treatment
Scorpions are venomous, with at least two types of scorpion poison. One is comparatively harmless to man. It causes sudden sharp pain, followed by numbness and local swelling, but after an hour or two the effects are usually gone unless the victim is a child or is a person who is unusually allergic to such venom. The other type is more serious, a neuro-toxic similar to the venom of the coral snake and the cobras. The symptoms from the neuro-toxic sting resembles strychnine poisoning and frequently results in death. Many yearly fatalities from scorpion stings occur in western Mexico, so one does need to be vigilant.
Scorpion stings can cause a wide range of conditions, from severe local skin reactions to neurologic, respiratory, and cardiovascular collapse. A sting from most scorpions usually results in a simple, painful, local reaction that can be treated with analgesics, antihistamines, and symptomatic/supportive care. Typical scorpion sting symptoms: immediate pain or burning, very little swelling, sensitivity to touch, and a numbness/tingling sensation. More serious type of venom symptoms include rapid breathing, high blood pressure and increased heart rate, involuntary muscle twitching, weakness.
If you are stung by any scorpion here are some immediate actions you should take:
- Wash the area of the scorpion sting with soap and water.
- Apply a cool compress on the area of the scorpion sting. Ice (wrapped in a washcloth or other suitable covering) may be applied to the sting location for 10 minutes. Remove compress for 10 minutes and repeat as necessary.
- If stung on a limb (arm or leg) elevate the limb to heart level.
- Seek medical attention.
- Keep your tetanus shots and boosters current.
Methods of Scorpion Control
If purchasing pesticides, look for those that specifically list scorpions (alacran in Spanish.) Ortho Home Defense is one commercial product, and the local veterinarian supply stores carry others. Some organic concoctions that help repel scorpions are:
- Use straight essential oil of cedar extract: Mix about ¼ teaspoon in 2 quart (1 liter) spray bottle. Spray around the doors and windows of the house, around outdoor areas the scorpions are likely to hide.
- Paul James, on HGTV suggests: Chop a dozen garlic cloves into 4 oz of mineral oil, let it seep for a day or two. Strain it (using coffee filters) into a half cup of water and add 4 drops of dishwasher liquid (Dawn is good.) Use a sprayer to apply.
There is no need to panic about scorpions- I have lived and gardened in the tropics for twenty years without being stung- it is just necessary to be aware and alert.