Tarantulas’ genitals are so long, it required a new genus

[Buster's Uncle]

Tarantulas’ genitals are so long, it required a new genus
Andrew Paul
Popular Science
Mon, August 4, 2025 at 1:30 PM EDT
2 min read



Satyrex Ferox was named for its particularly aggressive behavior.


It’s tough out there for male spiders. The sexual dimorphism is so extreme in many species that courtship frequently ends in death when they become a mate’s post-coital snack. However, arachnologists recently discovered four distinct tarantula species that evolved physical attributes to boost their survival odds. According to the team’s analysis, the spiders possess the longest genitalia of any known tarantulas—in one instance measuring almost four times as long as the upper portion of its body. The findings are described in a study published in the journal ZooKeys.

The species live across the Arabian Peninsula and Horn of Africa, all with especially elongated palps that differentiate them from other tarantulas. These appendage pairs sit at the rear a male spider’s thorax, and can transfer sperm to females during mating.



Satyrex speciosus is named for its bright coloration. Credit: Pavel Just


“Based on both morphological and molecular data, they are so distinct from their closest relatives that we had to establish an entirely new genus to classify them,” explained Alireza Zamani, an arachnologist at Finland’s University of Turku and study lead author.

The name of the new genus, Satyrex, isn’t particularly subtle. Zamani and colleagues fashioned it from a combination of satyr—the half-man, half-animal Greek mythological figure with a disproportionately large penis—and “rex,” the Latin word for king.

The naming specificity applies to some of the individual species, as well. The largest in the genus, Satyrex ferox, has a 5.5-inch legspan and nearly 2-inch palps measuring almost as long as a single leg. Ferox translates to “fierce,” and is indicative of the tarantula’s general demeanor.

“This species is highly defensive,” said Zamani. “At the slightest disturbance, it raises its front legs in a threat posture and produces a loud hissing sound by rubbing specialized hairs on the basal segments of the front legs against each other.”



S. arabicus can be found in Saudi Arabia. Credit: Ibrahim Mohssin Fageeh


Two of the other species, S. arabicus and S. somalicus, are named after their habitat regions, while S. speciosus is named for its bright coloration. In addition to the four new arachnids, Satyrex also includes a reclassified tarantula now known as S. longimanus and first described in Yemen in 1903.

“Satyrex longimanus, despite also having an elongated palp,was formerly classified in the genus Monocentropus, where the male palp is only about 1.6 times the length of the carapace and well within the typical range of 1.5 to 2 times seen in tarantulas,” Zamani added.

Although not fully confirmed, the researchers theorize the oversized palps may keep the males at a greater distance from “highly aggressive” females during mating, thus potentially giving them the space needed to make a quick escape.

https://www.yahoo.com/news/articles/tarantulas-genitals-long-required-genus-173007843.html