Researchers have just identified four new species of tarantulas whose genitals are so long they had to make a new biological classification for them.

Meet the Satyrex ferox, S. arabicus, S. somalicus, and S. speciosus. They hail from the Arabian Peninsula and the Horn of Africa and are so different from their closest relatives—on both the morphological and molecular level—that the team created a new genus for them, Satyrex.

“The genus name is a combination of Satyr, a part-man, part-beast entity from Greek mythology known for his exceptionally large genitals, and the Latin rēx, meaning king,” the researchers wrote in a study published last month in the journal ZooKeys.

Like Satyrs, the males of the four new species, as well as a fifth Satyrex species, have the longest known palps of all tarantulas. Palps are limbs that male spiders use to, among other things, transfer sperm while mating. Technically, palps are not penises but rather secondary sex organs. Satyrex ferox, whose legspan is around 5.5 inches (14 centimeters), has male palps up to 2 inches long (5 cm). For comparison, that’s almost as long as its longest legs.

Since male spiders, unlike male humans, probably don’t go around comparing their nether regions to each other, what’s the point of adorning such lengthy junk?

For S. ferox specifically, “we have tentatively suggested that the long palps might allow the male to keep a safer distance during mating and help him avoid being attacked and devoured by the highly aggressive female,” Alireza Zamani, lead author of the study and an arachnologist from the University of Turku, said in a Pensoft blog post (Pensoft published ZooKeys). Yes, you read that right.

“This species is highly defensive. 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,” Zamani added. In fact, ferox means “fierce.”

In other words, Zamani and colleagues suggest S. ferox may have evolved to have such long genitals because it allows them to have sex without getting eaten by their partner. Talk about a love bite.

In comparison, the other species’ names are more boring. Researchers named S. speciosus for their beautiful colors and S. arabicus and S. somalicus for their regions of origin. According to the study, the new genus also includes a fifth Satyrex—a known species previously classified in the genus Monocentropus, now called S. longimanus.

“The much longer palps of S. longimanus and the four newly described species were among the primary characters that led us to establish a new genus for these spiders, rather than place them in Monocentropus,” Zamani concludes. “So yes, at least in tarantula taxonomy, it seems that size really does matter.”