Spiders produce waste as a byproduct of their metabolic processes. These droppings can indicate their presence within a home or other structures, even when the spiders remain out of sight. Understanding their nature and appearance helps identify spider activity.
The Nature of Spider Excretion
Spiders excrete waste materials from their digestion of prey. Unlike many animals, spiders inject digestive enzymes into their prey to liquefy its tissues before consuming the fluid. This process results in waste that is primarily liquid or highly viscous.
Their excretory system allows them to combine both solid and liquid waste components into a single excretion. This method of waste elimination also serves as a water-conserving adaptation, as it helps spiders retain moisture.
The primary nitrogenous waste spiders produce is uric acid, a compound also found in birds and reptiles. Uric acid can be excreted as a semi-solid or dry material, helping spiders conserve water. A component of uric acid, guanine, can also be present, which may give the droppings a white or pasty appearance, especially once dried.
Identifying Spider Droppings
Spider droppings typically appear as small, dark spots or stains, often described as pinhead-sized splats or drips. They resemble tiny paint splatters, ink stains, or dark smudges rather than solid pellets. Their color can vary, commonly appearing in shades of black, dark brown, gray, or sometimes white, depending on the spider’s diet and species.
While wet, the droppings are thick and liquid, but they become dry and brittle as they age. When touched, dried droppings might feel grainy or gritty. Unlike the more uniformly shaped droppings of rodents, spider droppings lack a distinct, consistent form, often appearing as irregular spots or smears.
Common Locations for Spider Droppings
Spider droppings are typically found in areas where spiders are most active and spend significant amounts of time. These include surfaces directly beneath their webs, as waste often falls from the spider’s resting or hunting spot. Common indoor locations include interior walls, especially in corners, and on floors directly beneath corner webs.
They can also be observed on window sills, along baseboards, or under furniture and other large objects that are slightly elevated from the floor. In less disturbed areas, such as ceilings, or within undisturbed spaces like crawl spaces, attics, garages, and sheds, droppings may also accumulate.