Armadillidiidae

Distinguished from other woodlouse families (Oniscidea) by: (1) two-segmented antennal flagellum versus three segments in most other families; (2) modified uropod structure; and (3) ability to achieve complete conglobation. Most similar to pill millipedes (order Glomerida/Sphaerotheriida), but millipedes have two leg pairs per body segment versus one pair in isopods, and millipedes lack the distinct uropods visible at posterior. Armadillidiidae can be separated from other conglobulating isopods by antennal segmentation and uropod morphology.

Moist terrestrial environments including leaf litter, compost, decaying wood, soil crevices, and under stones or logs. Some species inhabit karstic regions with subterranean habitats; myrmecophilous species occur in sandy soils associated with ant colonies. Agricultural populations found in fields with crop residue and organic matter.

Native range centered on Mediterranean Basin with highest diversity there. Some European species have wider distributions. Armadillidium vulgare introduced to North America (first recorded in New England early 19th century) and now widespread throughout continent. Other introduced populations established globally. Some genera with restricted distributions: Schizidium in Iran and adjacent regions; Cristarmadillidium and Iberiarmadillidium in Iberian Peninsula.

Activity patterns vary by climate; generally more active during moist conditions. In temperate regions, adults overwinter in protected locations. Multiple generations per year possible in favorable conditions.

Primarily detritivorous, feeding on decaying plant matter including leaves and wood fibers. Some species consume living plant material, particularly seedlings, stems, shoots, roots, tubers, and fruits under wet conditions. Decaying animal matter, feces, shed skins, and dead insects consumed when available. Agricultural pest populations feed on soybean, corn, beans, squash, peas, melon, chard, beet, cucumber, potato, spinach, lettuce, and strawberry.

• Glycine max - pestSoybean seedlings damaged by feeding on cotyledons and stems; damage often mistaken for cutworm injury
• Various crop plants - pestSeedlings of corn, beans, squash, peas, melon, chard, beet, cucumber, potato, spinach, lettuce, strawberry fed upon; strawberry particularly susceptible to significant yield loss

Direct development without free-living larval stages. Females possess marsupium (brood pouch) on ventral surface where eggs are deposited and retained; developing young carried until sufficiently mature. Young emerge as miniature adults and undergo multiple molts to reach maturity. Overwintering typically as adults in soil or protected microhabitats.

Conglobation (rolling into ball) triggered by mechanical disturbance, vibrations, or pressure; serves as primary defense against predation and may reduce respiratory water loss. Nocturnal activity pattern; aggregates in moist microhabitats. Positive thigmotaxis (preference for contact with surfaces). Some species exhibit myrmecophily, living in association with ant colonies. Agricultural populations aggregate in crop residue and moist soil.

Primary role as detritivores accelerating decomposition of organic matter and contributing to nutrient cycling and soil organic matter retention. Balancing of soil carbon content through litter breakdown. Occasional pest status in agricultural systems, particularly affecting seedling establishment in soybean and other crops. Myrmecophilous species may benefit from ant association for dispersal and habitat access.

Beneficial in gardens and landscapes as decomposers. Occasional household pest when feeding on wooden structural elements. Agricultural pest of seedling crops, particularly in regions with heavy rainfall and flood conditions where populations flourish. Management in soybean achieved through increased seeding rates; chemical and biological controls show inconsistent effectiveness.

• Pill millipedes (Glomerida, Sphaerotheriida)Superficially identical conglobation behavior and ball-like form when disturbed, but possess two pairs of legs per body segment (isopods have one pair), lack uropods, and have three-segmented antennae
• Other Oniscidea (non-Armadillidiidae woodlice)Similar flattened body form and habitat preferences, but lack ability for complete conglobation and possess three-segmented antennal flagellum
• Perisphaerus (Blaberidae: Blattodea)Unrelated cockroach genus whose females exhibit convergent conglobation behavior; distinguished by six legs, winged males, and distinctly different head morphology

• terrestrial crustacean
• detritivore
• conglobation
• agricultural pest
• Mediterranean fauna
• introduced species
• myrmecophily

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• ID Challenge #18 | Beetles In The Bush
• Holy conglobulation, Batman! | Beetles In The Bush
• Integrated Pest Management Strategies for Pillbug (Isopoda: Armadillidiidae) in Soybean
• Pillbug, Roly-Poly, Woodlouse Armadillidium vulgare (Latreille) (Malacostraca: Isopoda: Armadillidiidae)
• Armadillidium fallax Brandt, 1833: Redescription, Synonymy, Distribution (Crustacea, Isopoda, Armadillidiidae)
• Armadillidium fallax Brandt, 1833: Redescription, Synonymy, Distribution (Crustacea, Isopoda, Armadillidiidae)
• Morphological and genetic characterization of a new Armadillidium species (Oniscidea, Armadillidiidae) from Tunisia
• Homoplasy and morphological stasis revealed through multilocus phylogeny of new myrmecophilous species in Armadillidiidae (Isopoda: Oniscidea)
• Aggregation and sheltering behavior of Armadillidium vulgare and Armadillidium nasatum (Isopoda: Armadillidiidae) exposed to fluorescent and ultraviolet light
• The genus Eluma in the Iberian Peninsula, with the description of a new terrestrial isopod: Eluma matae sp. nov. (Oniscidea, Armadillidiidae, Eluminae)
• Terrestrial isopods of the genus Schizidium Verhoeff, 1901 (Isopoda; Armadillidiidae) from the Hyrcaian Forest in northern Iran, including the description of a new species
• Description of Armadillidium boalense sp. nov. from northern Spain, with remarks and a key of the genus in the Iberian Peninsula and the Balearic Islands (Isopoda: Oniscidea: Armadillidiidae)