Spiders That Eat Other Spiders – A Common Yet Creepy Occurrence

Spiders eating other spiders may sound like something out of a horror movie but it’s actually quite common in the arachnid world. This gruesome behavior is known as spider cannibalism and occurs for a variety of reasons.

Overview

Spider cannibalism involves one spider consuming another spider, either of the same or different species. Some key points about spiders that exhibit cannibalistic behavior:

• Cannibalism occurs due to hunger, mating rituals, or territorial disputes.

• Females often eat the males after mating. This is known as sexual cannibalism.

• Spiderlings may eat unhatched eggs their own siblings, or even their mother.

• Larger spiders prey on smaller spiders as an easy food source.

• Web-invading spiders attack and eat the resident spiders in the web.

While not all spiders eat their own kind, cannibalism has been observed in many common spider species.

Why Do Spiders Eat Other Spiders?

Spider cannibalism serves an evolutionary purpose in some cases. Here are some of the main reasons spiders resort to eating each other:

• Hunger – When other food sources are scarce, spiders may view smaller individuals of the same species as quick and easy meals.

• Mating – Sexual cannibalism provides nutrients to support egg-laying. Females also eat the males to prevent future mating competition.

• Sibling Rivalry – Spiderlings consume unhatched eggs and their own siblings to reduce competition over resources.

• Territorial Disputes – Spiders are aggressive toward intruders. A web-owner will readily attack and eat an invading spider.

• Predation – Larger spiders prey on smaller spiders for nutrition the same way they eat insects. Jumping spiders actively hunt smaller spiders.

• Matriphagy – Spiderlings eat their own mother. This provides nutrients and teaches the spiderlings to hunt.

Common Spiders That Exhibit Cannibalism

While many spiders will resort to cannibalism if extremely hungry, some species are particularly prone to eating their own kind. Here are 7 spiders most likely to eat other spiders:

• 1. Black Widow Spider – Females are well known for eating the males after mating. The male sacrifices himself to ensure successful mating.

• 2. Redback Spider – Both sexes will aggressively fight conspecific intruders that enter their territory. The loser is eaten by the victor.

• 3. Wolf Spider – Females frequently eat the males after copulation. The much smaller males are easy prey.

• 4. Jumping Spider – Actively preys on smaller spiders of the same or different species for food.

• 5. Daddy Longlegs Spider – Invades the webs of other spiders, consuming eggs, prey, and even the resident spider.

• 6. Desert Spider – Males destroy the egg sacs of rivals. Females readily eat invading males.

• 7. Vampire Spider – High rates of cannibalism in both sexes. Males kill females to ensure their mate survives to bear offspring.

Cannibalism Between Different Spider Species

In addition to eating their own kind, some spiders make a habit of preying on other spider species. Here are 5 of the creepiest examples:

• Pirate Spiders – Invade the webs of other spiders. They eat the resident spider along with eggs and prey in the web.

• Portia Jumping Spiders – Cleverly stalk and ambush web-building spiders up to 200x their size.

• Marbled Cellar Spiders – Use stealth and agility to navigate sticky webs and attack host spiders within.

• Daddy Longlegs Spiders – Vibrate rival webs to mimic trapped prey. When the resident investigates, they attack.

• White-tailed Spiders – Nocturnal hunters that consume redback spiders, black house spiders, and various web-builders.

Methods of Spider Cannibalism

From deceitful lures to brutal ambushes, spiders have various tactics to catch and consume other spiders. Some approaches include:

• Web Traps – Web-builders like the black widow rely on sticky webs to ensnare wandering spiders.

• Vibration Lures – Daddy longlegs spiders pluck rival webs to mimic trapped prey, luring the resident spider within striking range.

• Stealth – Marbled cellar spiders carefully navigate sticky webs before ambushing the resident spider.

• Camouflage – Portia jumping spiders blend in with the web decor and stalk their victims.

• Surprise Attacks – Jumping spiders and wolf spiders surprise prey by pouncing without warning.

• Bites and Venom – Pirate spiders envenom web residents, while tarantulas paralyze spider prey.

• Entanglement – Spiders cocoon prey in thick layers of silk to subdue victims.

Is Spider Cannibalism Beneficial?

While unnerving, spider cannibalism does serve a purpose in many cases. Here are some potential benefits:

• Provides vital nutrients when other prey is scarce

• Maximizes the female’s reproductive success after mating

• Lowers competition between siblings and future generations

• Protects the resident spider’s territory and resources

• Allows spiderlings to develop vital hunting skills through matriphagy

• Controls spider populations in crowded habitats

• Keeps dangerous invasive spiders, like the hobo spider, in check

So while we may cringe at the thought, spiders eating other spiders is just part of their survival strategy. This creepy behavior helps maintain ecological balance.

The Takeaway

Spider cannibalism occurs more often than you may realize. Hunger, mating, sibling rivalry, and territorial disputes are just some of the reasons spiders end up eating each other. Sexual cannibalism is quite common, with Black Widows being prime examples. Larger spider species actively hunt smaller spiders too. And daddy longlegs are notorious for invading the webs of rivals and eating the resident spider. So next time you find spider carcasses in a web, chances are they were eaten by one of their own kind!