In many arachnid species, the male is the smaller of the two genders – much smaller. In these cases, the comparatively massive female will often devour the male after he’s done his job. Such species include the redback spider and the infamous black widow.
Recently, however, researchers have observed new behavior from tiny male spiders: mating with immature females.
The key to understanding this phenomenon is why the males sacrifice their lives during mating. Research has shown that if the male allows himself to be eaten after injecting his sperm, copulation is longer, ultimately allowing him to inject more sperm into the female. This helps ensure that his genetic signature will be passed on to another generation, which is basically the sole indicator for true biological success.
Maydianne Andrade is the researcher who first published findings on this activity, back in 1996. Recently, one of her students noticed a group of redback spiders mating with juvenile females. These females had fully-developed genitalia, but they were sealed. Further study revealed that the male spiders were using their fangs to forcefully open the females, mate, and then seal them off again, preventing other males from attempting to mate with her. What’s more, this process was found to cause no damage to the female.
In mating with immature females, the male redbacks ensured their own survival into the next generation, as well as in this one; they were able to escape with their lives after mating since the immature female would not try to consume him afterward.