# Common Shiny Woodlouse (*oniscus asellus*) The Common Shiny Woodlouse (Oniscus asellus) is a remarkably adaptable and widespread terrestrial crustacean. Far from being an insect, this fascinating little creature belongs to the subphylum Crustacea, making it more closely related to ocean-dwelling crabs and lobsters than to beetles or ants. It has adapted exceptionally well to life on land, finding its niche as a vital decomposer in both wild and human-altered environments. By voraciously consuming dead plant material, it plays a crucial role in nutrient cycling, breaking down organic matter and returning essential elements to the soil. Often overlooked as simple garden pests, these woodlice are actually harmless and highly beneficial scavengers. They are incredibly common across Europe and have been introduced to the Americas, where they thrive in moist, dark microhabitats. Observing a Common Shiny Woodlouse provides a direct window into the hidden, microscopic ecosystems of the forest floor and backyard compost heaps, highlighting nature's incredible ability to clean and renew itself. - **Category:** [Animal](https://www.snappit.app/explore/categories/animal) - **Rarity:** Common - **Danger:** 1/5 · Very low - **Snaps:** 7 - **Habitat:** Typically found in moist, shaded environments such as under rotting logs, stones, leaf litter, and compost heaps in woodlands, gardens, and urban spaces. ![Common Shiny Woodlouse](https://inaturalist-open-data.s3.amazonaws.com/photos/5656249/medium.jpg) Photo: Katja Schulz, CC BY 4.0 · [iNaturalist](https://www.inaturalist.org/photos/5656249) ## Appearance The Common Shiny Woodlouse is relatively large and flat, reaching up to 16 millimeters in length. As its name suggests, it is characterized by a glossy, shiny dorsal exoskeleton that typically ranges from dark grey to brown. The shell is often decorated with distinct paler, yellowish mottling, and the edges of its segmented armor form a continuous, light-colored "skirt" around its body. Unlike pillbugs, Oniscus asellus cannot roll itself into a tight defensive ball; instead, it relies on staying flat and clamping down against surfaces. Its head features moderately long, sharply angled antennae with three flagellar segments at the tip, which helps distinguish it from similar species. ## Taxonomy - **Kingdom:** Animalia - **Phylum:** Arthropoda - **Class:** Malacostraca - **Order:** Isopoda - **Family:** Oniscidae - **Genus:** Oniscus ## Interesting facts - Because they breathe using modified, gill-like structures called pleopodal lungs, they must live in damp environments to prevent these 'gills' from drying out. - Unlike the familiar pillbug, the Common Shiny Woodlouse cannot roll up into a ball; if threatened, its main defense is to clamp down incredibly tight against a flat surface. - Woodlice are terrestrial crustaceans, meaning they are more closely related to crabs, shrimp, and lobsters than to insects or centipedes. - Woodlice have copper-based blood utilizing hemocyanin rather than iron-based hemoglobin, which makes their blood appear pale blue when oxygenated. ## Special abilities - **Ammonia Gas Excretion:** Instead of urinating liquid waste, woodlice conserve water by excreting their nitrogenous waste as ammonia gas directly through their exoskeleton. - **Heavy Metal Tolerance:** They can accumulate and tolerate high levels of heavy metals like copper and zinc in their hepatopancreas, allowing them to survive in heavily polluted environments. - **Brood Pouch Rearing:** Females develop a fluid-filled marsupium (brood pouch) on their underside where they carry and protect their eggs and newly hatched young until they are ready to emerge. ## Measurements & details - **Length:** 1 cm - **Weight:** 0.00005-0.00015 kg - **Lifespan:** 2-4 years - **Clutch Size:** 20-60 - **Incubation:** 30-45 days ## Diet & Feeding They primarily consume dead and decaying plant matter, playing a critical role in nutrient cycling and soil health. - **Age differences:** Newly hatched young, called mancas, consume the same decaying matter but often eat their mother's feces to establish the necessary gut microbiome to digest woody material. - **Primary Foods:** Decaying leaves, Rotting wood, Fungi, Fallen fruit - **Foraging Method:** Foraging ## Ecological connections - **Eaten by:** [Woodlouse Spider](https://www.snappit.app/explore/woodlouse-spider) (*Dysdera crocata*) — Preyed upon specifically by specialized spiders with large fangs designed to pierce their tough exoskeleton. - **Eaten by:** Common Toad (*Bufo bufo*) — Consumed by small amphibians foraging in the leaf litter during the night. - **Eaten by:** [Common Shrew](https://www.snappit.app/explore/common-shrew) (*Sorex araneus*) — Eaten by small, highly active insectivorous mammals scurrying across the forest floor. ## Safety **Danger:** 1/5 · Very low No special safety notes yet. ## Frequently Asked Questions ### How to identify Common Shiny Woodlouse? Start with body shape, legs or fins, fur, feathers or scales, and standout markings. Then weigh size, habitat and where you saw it. Young animals and seasonal coats can look very different from familiar adults. Animal Identifier: upload a photo and compare the visible details. ### How long is Common Shiny Woodlouse? 1 cm ### How much does Common Shiny Woodlouse weigh? 0.00005-0.00015 kg ### How long does Common Shiny Woodlouse live? 2-4 years ### What does Common Shiny Woodlouse eat? They primarily consume dead and decaying plant matter, playing a critical role in nutrient cycling and soil health. ### Where is Common Shiny Woodlouse usually found? Typically found in moist, shaded environments such as under rotting logs, stones, leaf litter, and compost heaps in woodlands, gardens, and urban spaces. ### How does Common Shiny Woodlouse hunt? Foraging ### How many eggs does Common Shiny Woodlouse lay? 20-60 ## Where to spot - [Bean Hill Historic District](https://www.snappit.app/guides/places/bean-hill-historic-district) — Connecticut, US · Historic District - [Chelsea Parade Historic District](https://www.snappit.app/guides/places/chelsea-parade-historic-district) — Connecticut, US · Historic District - [Copicut Woods](https://www.snappit.app/guides/places/copicut-woods) — Massachusetts, US · Nature Reserve - [Jumel Terrace Historic District](https://www.snappit.app/guides/places/jumel-terrace-historic-district) — New York, US · Historic District - [Kal-Haven Trail](https://www.snappit.app/guides/places/kal-haven-trail) — Michigan, US · Trail - [Kennebunkport Historic District](https://www.snappit.app/guides/places/kennebunkport-historic-district) — Maine, US · Historic District [View all places to see Common Shiny Woodlouse](https://www.snappit.app/guides/where-to-see/common-shiny-woodlouse) ## More Animal - [Coquina](https://www.snappit.app/explore/coquina) (*Gymnoscelis coquina*) - [Crystal Jelly](https://www.snappit.app/explore/crystal-jelly) (*Aequorea forskalea Péron &*) - [Nautilus](https://www.snappit.app/explore/nautilus) (*Nautilus*) - [Sea Anemone](https://www.snappit.app/explore/sea-anemone) (*unclassified Amphianthus (in: sea anemones)*) --- Source: [Common Shiny Woodlouse: Facts & Places to See — Snappit](https://www.snappit.app/explore/common-shiny-woodlouse)