Armadillidium granulatum is properly a Mediterranean pill bug species that's become increasingly popular in the UK hobby. Native to islands and coastal regions across the Mediterranean — including the Balearic Islands, Sicily, Sardinia, and parts of Spain and Italy — they're properly hardy, attractive, and relatively forgiving for keepers stepping up from beginner species. Browse our A. granulatum product page for current UK stock.
What They Are
Armadillidium granulatum is a true pill bug — a conglobator that can roll into a tight ball when threatened. Key characteristics:
- Adult size — 15-20mm, slightly larger than common UK Armadillidium vulgare
- Body texture — distinctively granular/bumpy surface (hence "granulatum")
- Wild type colouration — grey to brown with yellowish/orange markings
- Hobby morphs — selectively-bred orange morphs particularly striking. Browse our orange morph product page
- Behaviour — moderately active, properly visible compared to some species
- Conglobation — full ball-rolling when disturbed
Geographic Origin Matters
Properly worth being clear about this since some sources get it wrong: A. granulatum is **Mediterranean**, NOT tropical. This significantly affects husbandry requirements. They're adapted to:
- Warm dry summers and mild wet winters
- Moderate rather than high humidity
- Calcium-rich limestone soils common across the Mediterranean
- Seasonal variation in moisture
Setting them up like tropical species (high humidity, constant warmth) properly causes stress, mould issues, and breeding problems.
Husbandry Requirements
Temperature
Properly comfortable across a wider range than tropical species:
- Ideal range — 18-24°C
- Acceptable — 15-26°C
- Tolerable for short periods — down to 12°C or up to 28°C
UK keepers can often maintain them at room temperature without supplemental heating, except in unheated rooms during winter.
Humidity
Properly Mediterranean species — they need MODERATE humidity, not tropical levels:
- Target — 50-65% relative humidity
- Humidity gradient essential — drier side (40-50%) plus moister side (60-70%) lets them choose
- Maintenance — mist the moister side every few days, let it dry partially between
- Critical — proper cross-flow ventilation to prevent stagnation
Properly common mistake: keepers giving them tropical humidity (75%+) often see colony decline, mould problems, and poor breeding. They need to dry out between mistings.
Substrate
- Base layer — coconut fibre or peat-free compost mix, 4-6cm deep
- Calcium additions — crushed limestone or shell pieces mixed in (properly important for this Mediterranean species)
- Top layer — generous oak, beech, or magnolia leaf litter
- Decaying hardwood pieces — proper dietary component
- Cuttlebone — always available as additional calcium source
Browse our accessories collection for substrate components, leaf litter, and cuttlebone.
Enclosure
- Size — minimum 5-10 litres for a starter colony (10-15 isopods)
- Ventilation — cross-flow ventilation essential
- Hides — cork bark pieces, lotus pods, real hardwood (NOT PVC pipes)
- No water dish needed — they get moisture from substrate and food
- No special lighting needed — they're nocturnal and active in ambient room light
Diet
Staple Foods
- Leaf litter — oak, beech, magnolia (essential foundation)
- Decaying hardwood — properly central dietary component
- Calcium sources — cuttlebone always available; crushed limestone in substrate
Supplementary Foods
- Vegetables — sweet potato, carrot, cucumber, leafy greens (in moderation)
- Fruits — apple, banana occasionally as treats
- Protein — fish flake or shrimp pellet sparingly (weekly or less)
- Specialised isopod foods — if using Repashy, properly the appropriate products are Morning Wood or Soilent Green (formulated for isopods/detritivores), NOT Grub Pie (which is an insectivore gel for reptiles/amphibians)
Properly key principle: variety over quantity. Remove uneaten fresh foods before they spoil. For broader diet context see our healthy diet article.
Reproduction — The Facts
Properly important to correct common misinformation here: A. granulatum reproduces sexually, not by parthenogenesis. Some older sources confuse this with Trichorhina tomentosa (Dwarf Whites), which IS parthenogenetic, but A. granulatum needs both male and female individuals to breed.
Reproductive Cycle
- Sexual maturity — typically 4-6 months from hatching
- Mating — male transfers sperm via gonopods to female's marsupium
- Brood time — eggs incubated in female's marsupium (brood pouch) for 21-45 days
- Brood size — typically 30-100 mancae per brood
- Breeding frequency — productive in good conditions, slower than Powder species
- Colony growth — moderate pace; properly reliable producers once established
Mancae Development
Young (mancae) emerge from the marsupium as miniature versions of adults. They:
- Have only 6 leg-bearing segments initially (gain the 7th pair after first moult)
- Are independent immediately on release
- Develop through successive moults rather than metamorphosis
- Reach adult size over several months depending on conditions
Properly no "neoteny" involved — they're not insects, they don't undergo metamorphosis, and there's no juvenile stage that bypasses adult form.
Difficulty Assessment
Properly intermediate-level isopods:
- Easier than Cubaris — more forgiving of variable conditions
- More demanding than Powder species — need proper humidity gradient and ventilation
- Good first Armadillidium — accessible without being basic
- Recommend 3-6 months hobby experience before attempting
Common Problems
Colony Decline
Most often traces to humidity issues:
- Too humid — properly the most common mistake. Setup like Cubaris (75%+) causes Mediterranean species to struggle
- Too dry — also problematic; need humid gradient
- Solution — establish proper gradient, ensure cross-flow ventilation, let substrate dry partially between mistings
Slow Breeding
Several possible causes:
- Insufficient calcium for egg production
- Inadequate dietary variety
- Temperature consistently below 18°C
- Recent colony stress
- Colony still establishing (give 3-6 months)
Mould Issues
Properly indicates excessive humidity or poor ventilation. Adjust ventilation rather than removing substrate. The granular texture of A. granulatum sometimes masks mould; check carefully if you suspect issues.
The Honest Summary
Armadillidium granulatum is properly:
- Mediterranean origin — not tropical, needs moderate humidity
- 15-20mm size — moderately sized Armadillidium
- Sexually reproducing — NOT parthenogenetic (that's Dwarf Whites)
- Conglobators — proper ball-rolling when disturbed
- Intermediate difficulty — 3-6 months experience recommended
- 50-65% humidity with gradient — NOT tropical 70-80%
- Worth knowing the morphs — wild type and selectively-bred orange morphs available
For UK keepers ready to move beyond basic species, A. granulatum offers proper Mediterranean character with distinctive granular texture and selectively-bred orange morphs. Browse our A. granulatum or orange morph products for current UK stock, or our wider Armadillidium collection for related species in the genus.
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