Spiders are cannibals. The vast majority of spider cannibalization happens before, during, or after mating where the female consumes the male; in rare cases, males will eat females after mating.
Female spiders commonly eat male spiders when the two mate. In response to that, male spiders have developed special techniques to avoid being eaten, such as mating with molting females that are smaller than males and are not able to eat them, and some males also play dead to stop cannibalism.
Non-reproductive cannibalism is also possible where spiders prey on spiders as they do on other animals of prey.
Types of Spider Cannibalism
1. Reproductive Cannibalism
Reproductive, or sexual cannibalism, is by far the more common of the two types of cannibalism.
It is performed in the majority of cases by females who will eat their male counterparts after breeding. Some of the species that practice reproductive cannibalism include:
- Black widow spiders
- Australia redback spiders
- Jumping spiders
- Burrowing spiders
- And some other types of spiders
In the vast majority of cases, females will eat males before, during, or after mating. Rarely, the opposite will be true where the males will be the ones performing the cannibalism. This is true with spiders that mate with females that are smaller than the males, such as jumping spiders.
It is believed that in the majority of cases, the female will kill the male after mating, but in some cases, the male will die naturally after copulation. Females will kill males with the use of venom, which they release during or after mating, which kills off the male and then the female eats the male.
Why this happens is unclear. It is likely just a pattern of some spider species that has been practiced for their entire evolution. That’s why males started using techniques like pretending like they’re dead after mating or only mating with molting females which are usually smaller than males.
Some spiders will die right after mating without the other partner eating it after dying. This can be said about the Latrodectus hasselti, a species that is more commonly known as the Australian redback spider.
This is seen as a sacrifice by the male for the “greater good”, but it is sometimes exaggerated and it is not always followed by cannibalism.
On very rare occasions, males will eat females after mating. This is only seen with a few species, while females are normally the ones that consume the males after or during the mating process.
Related: These 4 Wasps Eat Spiders!
2. Non-Reproductive Cannibalism
Non-reproductive cannibalism is spider cannibalism that happens naturally without spiders mating. This will be when spiders prey on other spider species for food, just like they do on other species they hunt for food.
On some rare and unique occasions, this will not happen because of predatory instincts.
For example, some spiders might be eaten by the offspring, or might also be eaten by the spiderlings if the mother spider dies after defending the eggs.
3. Predatory Cannibalism
Predatory cannibalism happens when one spider species preys on another spider species for food.
Sometimes, cannibalism occurs in the same species. For example, redback spiders will eat siblings right after hatching, and this is a heritable trait that some spiders are born with.
Daddy long-leg spiders will sometimes prey on the other members of the same species when food is scarce. They will resort to this mechanism when they can’t find other types of food around them, though.
Juvenile and adult females will sometimes be more aggressive towards males, which is seen as a sort of protective system that is meant to keep the males at bay. Some females, however, will go to great lengths with this mechanism and might even end up killing and eating the male instead.
Cannibalism between spider species is also not uncommon. Larger and more predatory spiders will prey on smaller spider species just like they would prey on other insects.
A good example is jumping spiders preying on web weavers. They have developed an interesting technique for eating web weavers. They would pretend as though they’re insects that have gotten caught inside a spider’s web, only to pounce on the web weaver as it comes to investigate the web.
4. Non-Predatory Cannibalism
Non-predatory cannibalism will rarely happen, but it will happen between spiders of the same species.
- The offspring of the species called Stegophydus Lineatus will eat their mother after hatching. This will especially happen when there is a shortage of food. Again, this mechanism is seen as a defensive mechanism and as a sort of sacrifice made by the mother to protect the offspring.
- Segestria florentina might get eaten by freshly-hatched spiderlings after dying while defending its hatch. When the female dies, the spiderlings will eat the body of the mother, which will make for an important meal for the offspring as there will be nobody to provide food for them.
There are many other cases of non-predatory cannibalism that happens between spiders of the same species. Female members are more inclined towards cannibalism, especially juvenile females.
This aggression can lead to cannibalistic behaviors later in the life of such a female spider, where the female might start preying on male spiders for no particular reason. But this is observed rarely and not with every spider species.
Spider cannibalism is possible, and it is not particularly rare, either. The most common type of cannibalism is when the female eats the male after or during mating.
There are many other instances where spiders will engage in cannibalism. Sometimes it is for food, which is when normally a larger spider would consume and prey on a smaller spider species.
Other instances are rare and will happen in extreme cases. One example is spiderlings eating their mother after the mother dies protecting its lair. It is certainly interesting to observe spider cannibalism and it has been spotted by many spider enthusiasts.