Theraphosidae

As of 2022, the World Spider Catalog has officially recognized the identification of 1041 species spanning 156 genera. This represents a remarkable diversity of species found across regions ranging from Australia to North America, displaying a wide range of sizes from as small as a thumbnail to as large as a dinner plate. However, what exactly distinguishes certain species as belonging to the Old World versus the New World, and what implications does this carry?

The terms "Old World" and "New World" originate from the 15th century, particularly with Christopher Columbus's monumental voyage. Upon his discovery of America on October 12, 1492, his return to Spain was heralded as the discovery of the New World. This concept swiftly permeated throughout Europe, symbolizing the exploration of previously unknown territories. Over time, as explorations continued and new lands were mapped, these terms gained increasing significance. Sailors navigating across the globe began to refer to lands on the opposite side of their hemisphere as either the Old World or the New World, a convention that has persisted to this day.

New World species

New World species inhabit the continents of North and South America, including Central America.

These species have evolved a defensive mechanism known as urticating setae. These small, hair-like structures possess barbed surfaces capable of easily penetrating skin and eyes, causing discomfort. When threatened, the spider rapidly rubs its back legs against the upper part of the abdomen, releasing a cloud of these barbed structures. This cloud is then carried by the wind to the skin, nose, or eyes of the perceived threat. This defensive adaptation compensates for their lower venom potency.

A bite from a New World spider is often likened to a bee sting, with the puncture wound causing more immediate pain than the venom itself. However, this does not diminish the need for respect, as some individuals may be allergic to their venom, requiring urgent medical attention. Common symptoms of a reaction include nausea, swelling, and localized pain. Additionally, New World species are generally characterized as slower-moving, with those possessing hairy abdomens often exhibiting a more docile nature.

Old World species

Species native to the Old World, spanning Europe, Africa, Asia, and Australia, exhibit distinct traits compared to their New World counterparts. While New World species are often noted for their calm and docile behavior, those from the Old World tend to be more aggressive and defensively inclined. These spiders typically have sparser hair coverage on their bodies and nearly bald abdomens, which precludes the use of urticating hairs for defense. However, they compensate for this with venom that is notably more potent.

When feeling threatened, Old World species commonly adopt a defensive posture, raising their first pair of legs with fangs poised for potential aggression.

The effects of a bite can vary from person to person, but commonly include excruciating pain, severe muscle cramps, localized swelling, difficulty breathing, and nausea. While fatalities from bites are rare, medical attention is often necessary to manage the symptoms effectively.

New World

North and South America, including Central America
Typically slower and often rather docile
More hair
Urticating setae
Less venom potency

Old World

Europe, Africa, Asia, and Australia
Fast
More aggressive nature
Less hair
No urticating setae
Higher venom potency