Armadillidium granulatum
A coastal Mediterranean pill bug with a granular texture — tolerant, hardy, and slightly more forgiving of dry conditions.
About this species
Armadillidium granulatum is a coastal Mediterranean isopod found along shorelines and in arid scrubland from southern Europe to North Africa. It is named for the granular, textured surface of its exoskeleton — noticeably rougher than the smooth A. vulgare. This species is often found in drier, more exposed habitats than other Armadillidium, giving it a higher tolerance for low humidity.
As an Armadillidium, A. granulatum can conglobate — rolling into a tight ball when disturbed. It is a terrestrial crustacean (not an insect) that breathes through gill-like pleopods. While it handles drier conditions better than most isopods, it still needs access to moisture — its pleopods must stay damp for gas exchange. Several colour forms are available, including wild-type grey and selectively bred variants.
Enclosure
A well-ventilated plastic tub with a 20x15 cm footprint is suitable for a starter colony. A. granulatum appreciates good airflow and tolerates drier conditions than most species — making it forgiving for beginners who tend to underwater rather than overwater. Provide cork bark, dried leaves, and cuttlebone. A small piece of limestone adds environmental enrichment.
Substrate
- 50% coco coir
- 20% organic topsoil
- 15% fine sand (reflects its natural coastal habitat)
- 15% crushed limestone or cuttlebone powder
Maintain a moisture gradient — one damp corner, the rest kept relatively dry. A. granulatum is one of the few isopods that genuinely tolerates drier conditions, but a moist retreat must always be available. Depth 5–8 cm, topped with dried hardwood leaves (oak, beech). Never use softwood — pine and cedar are toxic to isopods.
Feeding
- Dried hardwood leaves — staple diet
- Vegetables: courgette, carrot, sweet potato
- Cuttlefish bone — essential; Armadillidium species have heavily mineralised exoskeletons requiring consistent calcium
- Weekly protein: dried shrimp or fish flakes
Remove fresh food within 48 hours. Cuttlebone should remain permanently available.
Breeding
A. granulatum breeds at the typical steady Armadillidium pace — slower than Porcellio but reliable over time. Females carry eggs in a marsupium and produce moderate broods. A starter colony of 20 can grow to 50–80 within six to twelve months. The species is somewhat more forgiving of imperfect conditions than other Armadillidium, which helps with breeding success for less experienced keepers.