What Is an Opiliones? It Looks Like a Spider but Is Actually Not a Spider

Opiliones are small creatures that are frequently confused with spiders due to their external appearance, but are actually distant relatives of theirs. While spiders belong to the Araneae order, opiliones form their own separate order called Opiliones. At first glance, it can be difficult to tell these two groups of creatures apart, as both have eight legs and a similar body structure. However, for biologists, there are very fundamental and descriptive anatomical differences that separate these creatures from one another. Understanding these differences once again reveals how complex and fascinating the biological diversity in nature is.

Physically, opiliones have a small body in brown or reddish tones and long, thin legs. In their mouth region, they possess chelicerae, also known as small pincers. Although these features cause them to be mistaken for spiders, their body structure is actually quite different from that of spiders. While the bodies of spiders are divided into two distinct sections, the abdomen and the cephalothorax, the body of opiliones is in a single piece and shows no distinct segmentation. Additionally, the body size of opiliones is generally smaller than two centimeters; of course, this measurement is made without taking their very long legs into account.

One of the most important features that distinguish these creatures from spiders is that they can never spin webs or produce silk. In addition, since they do not have venom glands, they do not pose a danger of a venomous bite to humans or other creatures. Their mouth structure is quite small and has evolved solely to consume small food particles. Their eye structure also shows a major difference; while most spiders have six to eight eyes, opiliones have only two eyes, and the visual capacity of these eyes is extremely limited. For this reason, opiliones rely more on their sense of touch and their other senses rather than sight to perceive their surroundings.

The legs of opiliones have critical functions not only for walking but also for survival. The legs consist of many segments called tarsals, making them incredibly flexible. Although this flexibility allows the animal to move easily in different and challenging terrains, it can also cause the legs to break off easily. However, this breaking off acts as a defense mechanism rather than a disadvantage. When a predator or human grabs the leg of an opiliones, the leg can detach from the body and continue to move for a while, distracting the predator. In this way, the opiliones finds an opportunity to save its life and can continue its life normally even if it loses one of its eight legs.

There are thousands of different opiliones species worldwide, and these creatures prefer humid, low-light environments. Their feeding habits are highly diverse; they feed on organic matter such as leaves, seeds, and small insects. When threatened, they try to drive predators away by secreting a strong, sharp-smelling liquid from their special glands. Small spines found on the legs of some species can also aid in defense by causing superficial wounds. An interesting detail is that the second pair of legs, which is usually the longest, acts as a sensory organ, allowing the creature to perceive its surroundings much better.