House spiders are generalist predators, consuming a wide variety of prey. For the purpose of understanding their diet, “house spiders” typically refers to common, non-venomous species such as the long-bodied cellar spider (Pholcus phalangioides), the American house spider (Parasteatoda tepidariorum), and funnel weavers (Tegenaria species). These arachnids are opportunistic hunters that will attempt to subdue any organism they can overpower.
The Direct Answer: Are Ants Typical Prey?
Ants are generally not the typical or preferred prey for most common house spiders, though they are occasionally consumed. As opportunistic hunters, spiders will attack an ant if it becomes isolated, weakened, or inadvertently trapped in a web. Certain species, particularly more agile hunters like some jumping spiders or the black widow, prey on ants more frequently, often relying on potent venom or speed to overcome the ant’s defenses. However, for the majority of web-building house spiders, ants remain an uncommon food source compared to other insects.
Spiders that actively hunt on the ground, such as wolf spiders, may occasionally target solitary ants. The cellar spider, known for capturing larger prey like other spiders, has also been observed to eat ants when they become entangled in its loose web structure. Many spider species actively avoid ants, often selecting web locations free from ant chemical traces. This behavior suggests that the risk-reward calculation for ant predation leans toward avoidance for the average house spider.
Why Ants Are Difficult Prey
Ants possess several specific biological and behavioral defenses that make them a challenging and high-risk meal for most spiders. One major deterrent is their chemical defense system, which includes the ability of many species to spray or secrete formic acid. This acid can severely irritate or even kill a spider, making a close-range attack particularly dangerous. This chemical signal is so strong that some spiders can detect and avoid building a web in areas where ants have left chemical cues.
Ants also have a hard exoskeleton, which makes it difficult for a spider’s fangs to penetrate and inject venom effectively. Furthermore, ants are social insects that travel and forage in groups. An attack on one ant can quickly draw a coordinated, overwhelming response from its colony members, which can easily subdue and kill a solitary spider. This risk leads to the general avoidance of healthy, unisolated ants.
The Primary Diet of Common House Spiders
House spiders primarily consume soft-bodied insects that are easier to subdue and digest. The American house spider and other cobweb weavers rely on their sticky, three-dimensional webs to capture flying insects like flies, mosquitoes, and small moths. These light, soft-bodied creatures become quickly entangled, allowing the spider to safely immobilize them with silk and venom. This method minimizes the physical confrontation that is necessary when hunting ants.
Cellar spiders, despite their reputation for preying on other spiders, also readily consume mosquitoes and flies that wander into their loose webs. Other prey commonly found in the diets of house spiders include silverfish, small beetles, and earwigs. By focusing on these vulnerable insects, house spiders secure a meal with less risk of injury or energy expenditure.