A spider who spent a lot of time spinning in a Shakespearean theater once said, “O, what a tangled web we weave when we practice to cheat on our mates.” OK, the original quote isn’t from the Bard and this one isn’t from an arachnid, but recent research has uncovered new evidence of dwarf spiders using chastity plugs to keep their mates from web-hopping.
Gabriele Uhl of the Zoological Institute and Museum in Greifswald, Germany, discovered that male dwarf spiders (Oedothorax retusus) mate with females, then fill their two copulating ducts with a liquid that hardens into plugs which will theoretically block any other males from entering – kind of an insect chastity belt. Katrin Kunz, also of the Institute, recently joined with Uhl to study the effectiveness of these plugs and publish the results in an article in Springer's journal Behavioral Ecology and Sociobiology.
They found that the liquid used needs time to harden, resulting in different sizes of plugs. After the plugs hardened, they placed the females with other males for a time, then examined the females with an electron microscope.
Not surprisingly, they determined that bigger is better when it comes to chastity plugs. Smaller sizes can be removed completely by other males or shoved to the side in the heat of spider passion. The hardness of the plug also contributed to their effectiveness, so male dwarf spiders need to keep their pregnant mates pacified with dead fly candies until they’re fully protected, usually in about a day. Even if the rival male manages to force a small opening, their sperm still has a difficult time making its way down the duct that leads to the female sperm storage organ.
Kunz is impressed with the dwarf spider’s birth control device.
The mating plug in the dwarf spider clearly functions as a mechanical obstacle to rival males. Mating plugs are a powerful mechanical safeguard whose efficacy varies with plug size and age.
I wonder if a dwarf spider male ever thought about using this technique when its mate said, “We need to talk.”