Male Orb Weaver Spiders Detach Their Genitals And Leave Them Inside the Female

by Nabjot Kaur

Male Orb Weaver Spiders Detach Their Genitals And Leave Them Inside the Female

July 1, 2021

In a bizarre proposal to sex, a male orb weaver spider self-castrates its genitals and leaves it in the female spider. Male spider takes this approach to avoid being attacked by the female spiders who have a tendency of sexual cannibalism.

Nephilengys Malabarensis belongs to the species of tropical spiders of the Araneidae family. Araneidae have hairy legs, eight eyes and they lack stridulating organs. Nephilengys are usually found in or around human dwellings and they build their webs against tree trunks and walls. The size of their webs can go up to one or one and a half meters in diameter. The female Nephilengys are longer than the male spiders and their length ranges from 10 mm to 28 mm, while the males are only up to 5 mm long. Nephilengys species can be found in tropical Asia, in countries like India, Indonesia, Queensland, and Australia.

Nephilengys Malabarensis belongs to the species of tropical spiders of the Araneidae family.


The orb-web spider or Nephilengys Malabarensis species has been a subject of interest for its bizarrely unique way of mating since it got discovered. The male spider has detachable genitals, while the female spider displays sexually cannibalistic behavior. The male spiders have a pair of “Palps” which are sperm transferring organs. Palps are detachable. According to researchers, the female spiders can eat male spiders while they approach the females, due to which male Nephilengys leave their Palps in females and run away to escape this cannibalistic behavior of female spiders. A study states that the detached palps continue to release sperm into the female Nephilengys. Usually, only one of the two openings of female Nephilengys’ genitalia called the epigynum gets plugged, leaving some room for another male spider to inseminate her. After surviving the female cannibalism, the male Nephilengys stays nearby the female spider to protect her from other males who might be trying to knock out the palp plug to inseminate her.


“Prior work has indicated that eunuch spiders are superior fighters, we here identify a mechanism that enables eunuch’s considerable amount of endurance,” written by researchers in a paper published in June 2013, in the journal Biology Letters. “Our present results imply that the weight of Palps poses notable physical costs to males.”

Detachable Palps

This unique phenomenon made the researchers wonder if there are any other benefits related to it or is it solely present for mating? According to live science, researchers conducted a study to figure this out. Researchers took some male Nephilengys and amputated bot, one or none of their palps. After this they made them run around the lab by continuously nudging them with the paintbrushes until they got exhausted.

They discovered that removing one palp decreased the spider’s body weight by 4 percent while removing both palps or penises decreased their weight by 9 percent. On a positive note, their endurance increased by 32 percent in half-eunuchs and by a whopping 80 percent in full eunuchs.

Researchers then concluded that this approach of these spiders supports a “gloves-off” mating strategy. Nephilengys Malabarensis’ only goal is to protect their potential offspring from the harm of other male spiders. Detaching their palps helps them in reducing their body weight, thus helping them to run faster and fight off with other males who try to approach their females by any means.


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