Spider Feeding: How Spiders Eat & Digest Their Prey - A Detailed Guide

Spiders are obligate predators with a unique extra-oral digestion strategy. They cannot ingest solid food—instead, they liquefy prey externally and suck up the nutrient slurry.

The Feeding Sequence

1. Capture
   Web-building (orb, sheet, funnel, cobweb), active hunting (wolf, jumping, lynx), or ambush (trapdoor, crab spiders). Silk types vary: sticky capture spiral, non-sticky radii, dragline, egg sac silk.
2. Immobilization
   Venom injection via cheliceral fangs. Venom contains:
   
   • Neurotoxins — rapid paralysis (ion channel modulators)
   • Digestive enzymes — proteases, lipases, nucleases; begin tissue breakdown
   • Preservatives — antimicrobial peptides prevent spoilage
3. External Digestion (Pre-oral)
   Spider regurgitates digestive fluid (midgut enzymes) onto prey or injects it through fang punctures. Enzymes liquefy tissues over minutes to hours. Some spiders (e.g., Uloboridae) lack venom and rely entirely on mechanical maceration + regurgitated enzymes.
4. Suction Feeding
   Muscular pharynx (suction pump) draws liquefied meal through the narrow mouth into the esophagus. Filtering setae exclude solids.
5. Filtration and Transport
   Esophagus → sucking stomach (dilatable reservoir) → midgut diverticula (ceca) branching throughout prosoma and opisthosoma. Large surface area for absorption.
6. Absorption and Assimilation
   Nutrients cross midgut epithelium; hemolymph distributes to tissues. Lipids stored in fat body; proteins for silk, venom, cuticle.
7. Excretion
   Indigestible remnants (exoskeleton, wings) compacted into a fecal pellet (not "sperm"—a common error) and expelled via the anal tubercle. Uric acid (nitrogen waste) excreted by Malpighian tubules into hindgut.

Adaptations and Variations

• Web recyclers: Many orb-weavers eat their web daily to reclaim silk proteins.
• Specialists: Evarcha culicivora (vampire spider) targets blood-fed mosquitoes; Bagheera kiplingi is largely herbivorous (Beltian bodies).
• Fasting tolerance: Months without food; metabolic rate drops 70–90%.

Ecological Impact

Spiders consume 400–800 million tons of prey annually—comparable to human meat consumption. They are apex arthropod predators regulating insect populations globally.

Spider feeding is a marvel of biochemical engineering: venom as hypodermic needle + digestive fluid as external stomach + pharynx as pump.