THE IMPORTANCE OF SPIDERS ON ECOSYSTEMS

Spiders are the most diverse predators on Earth. With nearly 50,500 described species, they are present on every continent except Antarctica. Their diet is mainly based on insects. The role of spiders as predators of other arthropods is crucial for the functioning of ecosystems, since they regulate the populations of herbivorous insects.

Despite their important ecological role, these small animals trigger feelings of disgust and fear in a large part of the citizenry. In some cases, these reactions become a serious problem that can affect the daily life of the people who suffer from it. This is the case of arachnophobia, a disorder that, according to estimates, suffers up to 6% of the world population.

The cultural rejection that spiders arouse and that leads many people to kill them as soon as they see them is based on the fact that, supposedly, they constitute a threat to the physical integrity of people. According to those who defend this position, they are poisonous and attack humans. However, are these beliefs justified? Are spiders really dangerous to human health?

It is undeniable that almost all spiders have venom glands. Along with silk, it is an essential hunting tool for them. However, the venom is optimized to capture its most frequent prey, insects.

Since the venom arose in spiders millions of years ago, it has been filtered for many, many generations. In this way, increasingly efficient and precise insecticidal mixtures have appeared, since the poison is very expensive to produce in energy terms. But these animals have not been shaped by evolution to kill humans.

99% of species are not of medical importance to humans. That is, practically all the spiders in the world are completely harmless to humans. Most of them, regardless of having harmless poisons, are mechanically incapable of biting us. This is because they lack the strength to pierce human skin with their chelicerae, the name given to their mouthparts.

Only a few species of spiders, mainly located in Australia, due to their very particular evolutionary and ecological history, have highly toxic venoms.

Society's reticent attitude towards spiders is unjustified. Although a possible evolutionary origin of the fear of spiders has been hypothesized, the exact causes of this fear are still unknown.

A cultural origin of this rejection has even been raised, at least for some societies. In this way, re-education regarding the attitude towards spiders can change. A study published in 2019 has concluded that the positive message conveyed by characters related to insects and arachnids, such as the Marvel superheroes Ant-man and Spiderman, help reduce the symptoms of arachnophobia in children. In this study, children exposed to video clips related to these characters saw their phobic symptoms reduced compared to the control group.

The sensationalism with which everything related to spiders is usually treated contrasts with the ignorance of fundamental biological aspects about them. As an example is the number of spider species that are estimated to still be discovered. Currently, about 1,000 new spider species are described each year. Outreach activities and citizen science projects to study these information gaps are a good way to bring these animals closer to society, while generating very valuable information derived from the interest and active participation of citizens.