An univited visitor to our backyard
One evening we went to Usery Park to hear Ranger B, our favorite ranger, give another talk. This time the subject was scorpions. Scorpions are very interesting creatures. They are not insects. Insects have 6 legs. Scorpions are arachnids that have 8 legs. Since I knew nothing about them I was scared of them. Now I have learned a little about them so I am terrified of them. Not really. But sometimes ignorance is bliss.
There are about 1,400 scorpion species in the world. 80 can be found in the US. Of those 55 can be found in Arizona. In fact Arizona has more scorpions, rattlesnakes, bees, and tarantulas than any other state. Why are we here again? Ranger B says he mentions that enthusiastically to unwelcome relatives who threaten to visit him. I think he was joking. In Arizona scientists are looking so thoroughly that a new species or even 2 are discovered each year on average. Some have said, “Its time to stop looking!”
Scorpions have hairs on their body parts that act like ears. Through these hairs scorpions can “hear” an approaching organism. If it is big and makes the ground rumble, like a human for example, it knows what to do. It hides. I wanted to hear that. Scorpions are ambush hunters. They wait for prey to pass then by and then launch onto them. Scorpions are often very well camouflaged in their surroundings. Like our backyard!
Scorpions are extremely tough. That is part of the problem; if you consider them a problem. They can live up to 12,000 ft. in elevation. They can live in all kinds of habitats–deserts, forests, and even beachfront property.
Scorpions are among the toughest animals in the world. They can live an entire year without food. Scorpions have ben found under water where they appeared to be doing just fine.
Basically scorpions are nearly indestructible. They can’t even be killed by nuclear explosions. Scorpions can live for at least 2-4 weeks in a frozen state. That is why it might be surprising to some that none are found on Antarctica (at least so far). They can be killed with the human foot squashing them. That will do it. But be careful and avoid that stinger.
They are adaptable. That is why they have survived so long. They can be found on every continent except Antarctica and they might be found there if they could find food there.
As I found out scorpions can be detected with a black light. Our friend (at least he used to be our friend) Rick Molinski showed up at our home with a black light and then we learned we have scorpions in our back yard. I am not sure I wanted to know that.
Part of what interests me is their long and slow evolution. As Steven J. Prchal said,
Scorpions have changed little in the 350 to 400 million years since they first climbed from the primal seas and took their place among earth’s first terrestrial arthropods. 
Ancient scorpions were much larger than their modern descendants. A scorpion could reach 96 inches (8 ft.). I don’t know about you, but if scorpions were 8 ft. long I would not venture into my backyard at night. I would not go looking for them with a black light. I would stay in Manitoba!
Today the largest scorpion is the Emperor scorpion. They are not found in Arizona. They grow to 7.9 inches (20 cm) in length and weigh up to 30 grams. That is plenty big enough for my taste. Some people keep these as pets. I cannot understand why they would do that.
After gestation that they give live birth to their young. Typically, a mother scorpion can give birth to 8 live young. After they are born they often stick close to mom, often climbing on the mother’s back. When they are on the back they must cling tenaciously, for if they fall the mother is likely to eat them. These mothers are not likely to win the Mother of the year award.
The deadliest scorpion in of the 3 common ones in Arizona is the Bark scorpion (Centruroides exilcauda). It is the only one of the three whose sting is truly life threatening. It has a slender shape with long delicate pincers and tail. The others are larger and stouter, but actually less threatening. Sometimes size is not everything.
The bark scorpion prefers to climb and may as result be found many feet above ground on rock faces or trees. Bark scorpions display negative geotaxis, which means that they orient themselves upside down. People often get stung by picking up something and then getting stung by a scorpion clinging to the underside. After I heard this I decided I was not going to climb into our orange tree for oranges again.
Bark scorpions are so small that they can enter homes. If they do, be careful, very careful. Their venom is 150 times as dangerous as that of the Giant Hairy scorpion. This is what we did not like hearing.
Because the bark scorpion likes to climb and find cool places with airflows it can find its way into homes. Sometimes they are trapped in sinks or bathtubs or hiding in dark areas of the closet.
We should remember that scorpions don’t want to sting us. We are not prey for scorpions. They will only sting humans if they feel threatened by them. I don’t intend to frighten them on purpose. But it can happen accidentally. For example, some people pick up a piece of wood on which a scorpion is latched and it stings them when that happens. In such cases it sees us as a predators and stings us for defence.
The sting of the scorpion is usually not fatal, but it is extremely uncomfortable. 8,000 people are stung by scorpions in Arizona each year. Yet there has been only 1 known fatality caused by a scorpion.
As a result if you are stung by a scorpion don’t panic. You probably won’t die. You are 440,000 times more likely to die from heart disease than a scorpion sting, even if you live in Arizona. The only ones likely to be adversely affected are the very old or young. Don’t I fit into one of those categories?
If you get stung don’t go to the hospital unless you absolutely must. Hospital stays and anti-venom serums are very expensive. The stay and treatment could easily cost $40,000. Rather stay home, remain cool and collected (though in pain) and apply a cold compress. Only go the hospital if you end up in a state of shock. Then you must go to the hospital. Of course how will you get there if you are in a state of shock?
After all of this information I wondered was it worth it? Was it worth it to know what scorpions can do to you? Now I am worried. When we got home I looked on the ceiling, in my shoes, everywhere. Was I not better off when I was ignorant? I suppose that knowledge is always preferable to ignorance, but I wonder if that was really the case.
 Steven J. Prchal, “Scorpions,” in A Natural History of the Sonoran Desert, edited by Steven Philips and Patricia Wentworth Comus (2000) p. 262