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Basic arrangement of spider eyes, viewed from above. Most spiders have eight eyes, which tend to be arranged into two rows of four eyes on the head region. The eyes can be categorised by their location and are divided into the anterior median eyes (AME), anterior lateral eyes (ALE), posterior median eyes (PME), and posterior lateral eyes (PLE).
Spiders also have several adaptations that distinguish them from other arachnids. All spiders are capable of producing silk of various types, which many species use to build webs to ensnare prey. Most spiders possess venom, which is injected into prey (or defensively, when the spider feels threatened) through the fangs of the chelicerae. Male ...
Spiders do not have compound eyes, but instead have several pairs of simple eyes with each pair adapted for a specific task or tasks. The principal and secondary eyes in spiders are arranged in four, or occasionally fewer, pairs. Only the principal eyes have moveable retinas. The secondary eyes have a reflector at the back of the eyes.
In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively. [ 13 ] Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up.
Eyes: The basic number of eyes is eight, typically arranged in two rows (e.g. as in Gnaphosidae); the front row are the anterior eyes, the row behind the posterior eyes; the four eyes to the edges are the lateral eyes, the four eyes in the centre the median eyes; the anterior median eyes are called the main eyes or direct eyes, while the other ...
Spiders could, theoretically, eat every single human on earth within one year. It gets worse. Those humans consume about 400 million tons of meat and fish each year, so ultimately, the tiny ...
Jumping spiders have four pairs of eyes; three secondary pairs that are fixed and a principal pair that is movable. The posterior median eyes are vestigial in many species, but in some primitive subfamilies, they are comparable in size with the other secondary eyes and help to detect motion. [10]
With so many kinds of eight-legged bugs running around (nearly 3,000 species in North America alone!), the most common house spiders are bound to pop up in your abode from time to time. And with ...