Minibeast Profiles: Scorpions
by Gary A. Dunn, M.S., F.R.E.S., Director of Education
Most people are not too fond of scorpions. In fact, many people are afraid of scorpions because of the sting located at the tip of their abdomen. However, most scorpions are relatively harmless and pose no serious threat to humans. Scorpions do not attack humans; they only sting to catch their food or to protect themselves. Scorpions have been inhabitants of this planet for at least 300 million years, so they were here long before humans.
The desert hairy scorpion, Hadrurus arizonensis
Scorpions, like insects, belong to the large group of animals known as arthropods. Both have hard exoskeletons, segmented bodies and jointed legs. Insects have 6 legs, 3 main body parts, compound eyes, antennae, and wings (usually). Scorpions, on the other hand, have 8 legs and 2 main body regions. They lack compound eyes, antennae, and wings.
Scorpions are more or less elongate and flattened. The head and thorax are joined together into one large body section called the cephalothorax. The front half of the body (cephalothorax and front of the abdomen) are broad, while the last six segments of the abdomen are formed into a slender tail (with sting). Scorpions have two special mouthpart structures: tiny mouth pincers (called chelicerae) and large, claw-like pincers (called pedipalps). The pedipalps are held out in front of the body and even though they might look like legs, they are not. The head also has 6 simple eyes, two in the very center and two at each of the front corners of the cepahalothorax. The eight legs are also attached to the cephalothorax. When resting, a scorpion's tail is laid to the side. When scorpions are hunting (or threatened) the tail is carried up over the back with the stinger directed forward. The sting can be moved in every direction except backwards.
Most scorpions are plainly colored - light brown, yellowish, dark brown, or black. Some are smooth and shiny and others are hairy. They range in size from less than 1/2" up to 8" in length. The world's largest scorpion is the emperor scorpion of Africa. Scorpions only occur in the warm regions of the world. A total of 56 species of scorpions are known from the United States and they are found in the western, southwestern, and southeastern states. Worldwide there are about 1200 species of scorpions. There is no relationship between the size of a scorpion and how dangerous it is. Many big scorpions are harmless, while many small ones are deadly. The only dangerous species in the United States is the slender scorpion, Centruroides sculpturatus, which occurs mostly in Arizona, but also in California, New Mexico, and Texas. It is pale yellowish-tan, slender, and 1/2" to 3" long.
Scorpions are active at night. During the day they hide in burrows in the sand, or under stones or logs. They are also common under dried cow manure, a fact I discovered while collecting beetles in Arizona many years ago. Their hiding places protect them from the hot daytime temperatures. As the sun goes down scorpions emerge from their burrows and begin hunting for food. They move about slowly and steadily. While most move about on the ground, some are excellent climbers and hunt on tree trunks and foliage. They do not see very well and must locate their prey by vibrations. Their legs are covered with tiny hairs that direct them to the source of any vibrations. They grab the prey with their pedipalps (claws); if the prey struggles they will sting and paralyze it so that it can be eaten. They feed mainly on insects, but some scorpions have been known to feed on mice, lizards and small snakes. Scorpions don't need much food, and they often go for weeks (even months) between meals. Some can go without food for a whole year and still go on living.
All scorpions "glow" under blacklight
Baby scorpions hatch from eggs carried within the body of their mother and the young scorpions crawl onto her back for protection. Those that are not careful are sometimes eaten by their mother. These larval scorpions have short legs and tails and no claws. The sting is present but they cannot sting yet. After two weeks they molt and develop into young scorpions, complete with working sting and claws. They will molt seven to nine more times (over a period of 2 to 3 years) before becoming an adult. As adults they may live for another 5 to 8 years.
Scorpions are not without their own enemies. Many scorpions eat other kinds of scorpions and some are cannibalistic. Centipedes are a major enemy of scorpions, and some birds and mammals (shrews and monkeys, for example) have learned to avoid the sting and love eating scorpions.
| This educational resource was prepared by the Young Entomologists Society, 6907 West Grand River Ave., Lansing MI 48906-9131, phone/fax 517-886-0630, e-mail YESbugs@aol.com. Support minibeast youth education - join Y.E.S. today! |