Spiders are predators found in nearly all terrestrial environments. While primarily known for consuming insects, some spider species do prey on slugs, though this is not a universal behavior. The question of whether these hunters include slugs in their diet is nuanced.
Spiders and Slug Predation
Specific spider types prey on slugs, especially ground-dwelling species or those in damp environments where slugs thrive. Wolf spiders (Lycosidae) are observed to consume slugs, using active hunting strategies. Certain larger mygalomorph spiders also include gastropods in their diet, with slugs and snails representing a notable portion for some. Orb-weaving spiders like Meta menardi and Meta bourneti, found in dark, confined spaces, feed on slugs when other prey is scarce.
The slimy mucus produced by slugs presents a challenge, making it difficult for many spiders to get a firm grip or for venom to penetrate effectively. The hard shells of snails, closely related to slugs, generally deter most spiders from preying on them, though some specialized harvestmen can crush shells. While slug tissue is palatable, the physical and chemical defenses of gastropods mean they are rarely preyed upon by most spiders.
Spider Dietary Habits
Spiders are generally opportunistic predators, meaning their diets are diverse and largely depend on the availability of prey in their environment. Their primary food source consists of insects, including common pests like flies, mosquitoes, ants, moths, beetles, and cockroaches.
Beyond insects, larger spider species may occasionally consume small vertebrates such as lizards, frogs, birds, fish, or even bats. Some spiders also prey on other spiders, and a few species, like the jumping spider Bagheera kiplingi, have a largely herbivorous diet, feeding on plant materials like nectar or pollen. Collectively, the global spider community is estimated to consume between 400 and 800 million metric tons of prey annually, with insects making up over 90% of this biomass.
Factors Influencing Prey Choices
Several factors determine a spider’s prey choices, including the abundance of available food. Spiders tend to select habitats with high prey availability, and their feeding frequency increases when prey is plentiful. The size of the spider also plays a role, with larger spiders generally consuming larger prey items. Different spider species exhibit distinct prey preferences based on their biological traits and hunting strategies.
Environmental conditions significantly influence spider activity and prey encounters. Damp, humid environments are favorable for many spider species, supporting their hunting and web-building activities, and often correlating with higher prey populations. Extreme weather events can disrupt habitats and alter prey availability, forcing spiders to adapt or relocate. A spider’s hunting strategy, whether it’s a web-builder waiting for prey or an active hunter like a wolf spider, also dictates the types of prey it can successfully capture. The behavior and potential toxicity of prey can also affect a spider’s decision to pursue it.