Overview
This lecture covers the identification, biology, habits, and significance of the pillbug (Armadillium vulgare), a non-native terrestrial crustacean found in Colorado.
Identification and Description
- Pillbugs have armored, blue-gray bodies with seven pairs of similar legs and prominent plates.
- They possess two pairs of antennae, one much longer than the other, and simple eyes (ocelli) for minimal vision.
- Terminal appendages called uropods project from the tip of their fused abdomen.
Distribution
- Originally native to Europe, pillbugs are now found statewide in Colorado and widely across North America due to introduction.
Life History and Habits
- Pillbugs are scavengers that feed mostly on moist, decaying plant matter and occasionally on garden seedlings.
- They play an important role in recycling nutrients by helping decompose dead plant material.
- Feeding occurs at night; during the day, they hide under covers or come out in overcast or wet conditions.
- Pillbugs acquire oxygen via gills that need to stay wet, restricting them to moist environments.
- Uropods help wick up water, allowing them to drink from both ends of their body.
- They overwinter as adults under shelter and become active in spring, mating and producing eggs.
Reproduction and Development
- Females lay about two dozen eggs at a time, carrying them in an abdominal pouch called a marsupium.
- Young stay in the marsupium for 6-7 weeks before leaving.
- Pillbugs molt in two stages: front half, then rear half, giving them a temporary two-toned appearance.
- Molting occurs every two weeks for juvenile stages, becomes irregular in adults, and continues throughout their 2-3 year lifespan.
Notable Behaviors and Related Species
- Pillbugs can roll into a ball as a defense mechanism (hence "roly-poly").
- Commonly mistaken for sowbugs, which cannot roll into a ball and have a flatter body.
- Related aquatic isopods exist, but most are native and live in water.
Key Terms & Definitions
- Pillbug — Armadillium vulgare, a terrestrial crustacean with the ability to roll into a ball.
- Uropods — Tail-like appendages at the abdomen’s tip, helping in moisture uptake.
- Marsupium — Specialized pouch on the female's abdomen for carrying eggs and young.
- Ocelli — Simple eyes used only to detect light, not form images.
- Molting — The process of shedding the exoskeleton to grow; occurs in two stages in pillbugs.
- Sowbug — Related species (Porcellio scaber, Oniscus asellus) that cannot roll into a ball.
Action Items / Next Steps
- Review pillbug identification characteristics and life cycle for possible quiz.
- Observe pillbugs in natural environments for behavior and habitat noting.
- Read about related isopod species for broader understanding.