Spiders are successful generalist predators inhabiting almost every terrestrial ecosystem, making them one of the most abundant groups of carnivores. They use silk and venom to subdue a massive variety of prey, primarily insects. Moths present a challenging prey due to their protective layer of fine, powdery scales. Understanding how these hunters deal with this defense reveals fascinating evolutionary adaptations.
Yes, Spiders Eat Moths: Overcoming Wing Scales
Moths are a regular part of the diet for many spider species, but they present a unique defense against standard web capture. Moth wings are covered in minute, dust-like scales that easily detach and coat the sticky silk strands of a web. This quickly neutralizes the web’s adhesive properties, allowing the moth to escape.
Spiders relying on webs counteract this defense by rapidly swathing the captured moth in sheets of non-sticky silk. This rapid immobilization binds the wings and legs to the body before the moth can shed enough scales to break free, preventing disruptive fluttering.
Once secured, the spider injects venom to paralyze the moth, followed by digestive enzymes that liquefy the internal tissues. The spider then sucks up the resulting liquid meal, leaving behind the indigestible exoskeleton and wing scales. Specialized species, like the orb-weaver Cyrtarachne akirai, produce a highly adhesive glue designed to seep beneath the moth’s scales, anchoring the insect securely.
Specialized Moth Hunting Techniques
Certain spiders have evolved highly specialized hunting strategies focused almost exclusively on moths, moving beyond general web capture. The most famous specialist is the Bolas Spider (Mastophora). These spiders do not construct a traditional orb web; instead, they use aggressive chemical mimicry to lure prey.
A female Bolas Spider hangs from a silk line and swings a single strand of silk, or “bola,” tipped with a sticky, pheromone-laced globule. This globule emits a precise blend of volatile organic compounds that mimic the sex pheromones used by female moths. The spider deceives male moths, who are drawn in believing they are approaching a receptive mate.
The spider can adjust the chemical blend to target different species of male moths active at various times of the night. As the moth approaches the attractive scent, the spider swings the sticky bola, lassoing the insect out of the air. This specialization allows the Bolas Spider to capture prey often much larger than itself, bypassing the need for a scale-clogging web entirely.
The Broader Spider Diet
Moths are a notable food source, but spiders are opportunistic generalists whose diet is limited mainly by prey size and local availability. Their diet consists primarily of other arthropods, including common insects like flies, beetles, and grasshoppers. Global spider populations are estimated to consume between 400 and 800 million metric tons of prey annually.
The specific hunting style dictates the diet’s composition. Passive hunters, such as orb-weavers and funnel-web spiders, rely on the chance entanglement of insects in their stationary silk structures. Active hunters, like wolf spiders and jumping spiders, stalk or ambush their prey, often using acute vision and speed rather than silk for initial capture.
Larger species, such as the Goliath bird-eater tarantula and fishing spiders (Dolomedes), expand their menu to include small vertebrates. These giants have been documented preying on frogs, small reptiles, fish, and small mammals. A rare exception to the carnivorous rule is the jumping spider Bagheera kiplingi, the only known spider whose diet is predominantly herbivorous, feeding primarily on Beltian bodies found on acacia plants.