Tag: mating

New tarantula species so feisty, males evolved the longest genitalia to survive mating

Four new species of tarantulas have been discovered, highly unusual due to their male sexual organs, which are the longest known among all tarantulas.

Four new species of tarantulas have been discovered in the Arabian Peninsula and the Horn of Africa. But these aren’t just any tarantulas.

  • Satyrex arabicus, male, Saurdi Arabia. Photo by Ibrahim Mohssin Fageeh
  • Satyrex ferox, male, Oman. Photo by Bobby Bok
  • Close-up view of a dark-colored tarantula spider with hairy legs.
    Satyrex speciosus, male, Somaliland. Photo by 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, and we named it Satyrex,” explains Dr. Alireza Zamani of the University of Turku, who led the study that discovered them.

A person holds a large, dark spider in a lab setting, with spider webs and nature-themed artwork in the background.
Satyrex ferox, male.

The genus name is a combination of Satyr, a part-man, part-beast figure from Greek mythology with exceptionally large genitalia, and the Latin word rēx, meaning “king.”

But why “king,” and why a Satyr? “The males of these spiders have the longest palps among all known tarantulas,” Dr. Zamani says. Palps are the specialized appendages used by male spiders to transfer sperm during mating. In Satyrex ferox, the largest species in the genus with a legspan of about 14 cm, the male palp can reach an incredible length of 5 cm, which is almost four times longer than the front part of the body, and almost as long as it longest legs.

The name ferox means “fierce”, and it fits. “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,” Dr. Zamani explains.

Satyrex ferox. Video by Mark Stockmann

“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.”

As for the others in the group — the researchers named S. arabicus and S. somalicus after their respective regions of origin, while S. speciosus gets its name from its bright and beautiful coloration. The genus also includes an older species, S. longimanus, originally described from Yemen in 1903 and previously placed in a different genus.

Satyrex speciosus, female, Somaliland. Photo by Přemysl Fabiánek

“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. 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. So yes, at least in tarantula taxonomy, it seems that size really does matter,” Dr. Zamani says in conclusion.

All members of this genus are fossorial, meaning they live underground, in burrows at the base of shrubs or between rocks.

The study was published in the open-access journal ZooKeys.

Research article:

Zamani A, von Wirth V, Fabiánek P, Höfling J, Just P, Korba J, Petzold A, Stockmann M, Elmi HSA, Vences M, Opatova V (2025) Size matters: a new genus of tarantula with the longest male palps, and an integrative revision of Monocentropus Pocock, 1897 (Araneae, Theraphosidae, Eumenophorinae). ZooKeys 1247: 89-126. https://doi.org/10.3897/zookeys.1247.162886

To be fragrant or not: Why do some male hairstreak butterflies lack scent organs?

Female butterflies generally choose among male suitors, but in the tropics with hundreds of close relatives living in close proximity, how can they decide which males are the right ones? After all, if she mates with a male of another species, she is unlikely to have surviving offspring. One solution is that males of some species have scent producing organs on their wings, so if a male has the right smell, the female will presumably be receptive to his advances. Strangely, males of some species lack these scent producing organs, which would seem to be a huge disadvantage.

Biologists have theorized that when a species loses a male scent producing organ during evolution, its closest relatives do not occur in the same places. In other words, the female does not have to choose among males of the most closely related species, and the males do not devote energy to producing scents.

A team of researchers, led by Dr. Robert Robbins from the Smithsonian Institution, digs into this question in a small group of Latin American butterflies in a study published in the open access journal ZooKeys. Two newly discovered representatives in this butterfly group possess scent pads while their closest relatives do not. The researchers report that scent pads were lost evolutionarily twice in this group, and as predicted, in each case, the species without the scent pad does not co-occur with its closest relative. The present study adds more evidence to accumulating support for the explanation why some males lack scent pads.

Evolutionary losses, such as the one observed herein in Thereus oppia and related butterflies, are quite common, as Dr. Robbins and collaborators have observed in a previous research. Such disappearances of male secondary sexual features have been explained by geographic isolation of a species from its closest relatives, and the butterflies in this study are no exception.

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Original source:

Robbins RK, Heredia AD, Busby RC (2015) Male secondary sexual structures and the systematics of the Thereus oppia species group (Lepidoptera, Lycaenidae, Eumaeini). ZooKeys520: 109-130. doi: 10.3897/zookeys.520.10134