Jumping spiders have over 6,200 described species making up 13% of all spiders. They have the best vision of all spiders having four pairs of eyes, with the anterior median pair (pertaining to or toward the head or forward end of the body) being particularly large.
Many people are afraid of spiders, especially ones that can jump several times the length of their body which is usually about 0.04–0.98 inches. They are found all over the world except for the extreme North and South poles. They do prefer tropical forests.
There are over 300 species known to the United States living mostly outdoors. They are carnivores eating smaller insects and spiders. Jumping spiders do not generally bite unless they are startled. Their bite symptoms are mild and heal quickly.
Included in the family Salticidae they are relatively smaller than other spiders. With their impressive vision, they don’t need to build webs for hunting. They spot their prey and pounce on it. How do these spiders jump? One theory on their jumping is that they increase the blood pressure in two or four of their back legs, which expands the legs to give their leaps a boost. Jumping spiders are able to employ bimodal breathing – taking in oxygen via arachnid book lungs and a tracheal system. They also spin a single thread to stabilize the jump.
Grasshoppers use special leg muscles to perform their jumps. Jumping spiders don’t have these muscles. They also spin a quick line of silk that they use as a dragline.
The tension in the silk line allows the spiders to adjust their body for a smooth landing. It also provides direction and allows the spiders to stabilize their landing in addition to acting like a sort of safety net if they need to stop mid-jump.
Jumping spiders are generally diurnal, active hunters. They will spin tiny tents or shelters to protect them from rain or nighttime predators. They also use these “cocoons” to lay their eggs and raise their young.
Jumping spiders are smart and have the ability to learn
- Many jumping spider species plan specialized routes to reach their prey rather than just rushing in on it. This quality is usually only observed in larger predators. They can even visualize where hidden prey might be hiding and find them.
- Jumping spiders act out elaborate dances to attract a mate. Usually, animals that small don’t have the visual acuity to utilize such a technique. The Australian peacock jumping spider is the size of a grain of rice. It has a colorful fan on its back which it expands and dances with. It may dance for almost an hour, but if the female doesn’t like the dance, she eats the male spider!
- Scientists in New Zealand developed an obstacle course, which jumping spiders navigated successfully. The maze consisted of towers, platforms, moats (jumping spiders don’t like to get wet), and containers of food. Their ability to plan and adapt when plans must change is called “genuine cognition.” It means they think before they act.
- Jumping spiders have good memories. In the above study, spiders sought out the container which had had food in it, even after researchers had replaced it with an empty container.
- Jumping spiders display site fidelity, meaning that if they find a good place to hunt or nest, they will return there if displaced.
The smaller set of eyes provides a wide-angle view and a sense of motion, while the larger, primary eyes in the center of the spider’s head provide a massive amount of detail in color and the best spatial acuity of any animal of similar body size.
Sensory hairs along their bodies take in the vibration of sound waves, an action that sends signals to the spiders’ brains. Researchers studying the spiders’ eyes discovered this accidentally in 2016. They were demonstrating that vibrations sent the spiders’ neurons firing, even vibrations that originated as far as 10 feet away, leading them to conclude that the spiders could feel the sound waves.
- A book lung is a type of respiration organ used for atmospheric gas exchange that is present in many arachnids, such as scorpions and spiders. Each of these organs is located inside an open ventral abdominal, air-filled cavity (atrium) and connects with the surroundings through a small opening for the purpose of respiration. [Back]
- Diurnality is a form of plant and animal behavior characterized by activity during daytime, with a period of sleeping or other inactivity at night. [Back]
- The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite. It dates from 44 million years ago (during the Eocene epoch). It has been estimated that these forests created more than 100,000 tons of amber. Today, more than 90% of the world’s amber comes from Kaliningrad Oblast of Russia. It is a major source of income for the region; the local Kaliningrad Amber Combine extracted 250 tons of it in 2014, 400 tons in 2015. [Back]
- The Eocene Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago. It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name Eocene comes from the Ancient Greek, “dawn” and “new” and refers to the “dawn” of modern (‘new’) fauna that appeared during the epoch. [Back]