Formosan Patterned Cockroach

🔤 Taxonomy

Paranauphoeta formosana Matsumura, 1913 is accepted by GBIF and the Blattodea Species File. Taiwan’s biodiversity catalogue also records Paranauphoeta shelfordi as a synonym. “Assassin-mimic cockroach” is a hobby name for its narrow, long-legged outline and contrasting pattern; it does not mean that this species is a specialist predator.

📌 Description

Adults are about 2.4-2.8 cm long, glossy dark brown to black, with pale markings and reddish legs. Both sexes have developed wings and run and climb quickly. Sexing is safest from the underside: mature males retain terminal styli and have a narrower abdomen, while females are broader. Avoid identifying sex from colour alone.

The colony is more sensitive to stagnant wet conditions than its tropical origin might suggest. It also reacts to disturbance with sudden bursts of speed. Those two traits—ventilation and containment—matter more than elaborate decoration.

🌍 Distribution

The verified native record is Taiwan, where the Taiwan Biodiversity Network treats the species as native. Published taxonomic material also cites specimens from Formosa/Taiwan. The map therefore highlights Taiwan only; seller claims from elsewhere should not be added to the native range without voucher-backed records.

Range map

⚖️ Legal status

Checked on 2026-08-22: P. formosana was not found in the CITES Appendices, EU wildlife-trade Annexes A-D, the EU list of invasive alien species of Union concern, or the Bern Convention appendices. These checks do not cancel national rules for importing, transporting, selling, or keeping live non-native insects.

Buy a named captive culture and retain the invoice, breeder details, and import documents. Never release cockroaches or living substrate. Freeze unwanted animals and used substrate in a sealed bag before disposal where local rules permit.

🤌 Husbandry

A group of 10-20 can start in a 30 × 20 × 25 cm enclosure. Use a gasketed or clipped lid, ventilation apertures covered with fine metal mesh, and a smooth-wall barrier below the rim as backup. Work over a larger catch tub; an animal on the lid can be out of reach before the lid is put down.

Parameter	Practical target
Adult size	2.4-2.8 cm
Main air temperature	23-28 °C
Limited warm side	28-30 °C
Night	20-24 °C
Moisture	50-70% RH; one moist lower corner
Substrate	5-8 cm with leaves and bark
Feeding	dry staple plus fresh food every 2-4 days

Quarantine additions for about 60 days using separate tools. Keep culture lines and other Paranauphoeta species apart: hybrids or misidentified nymphs destroy locality and taxonomic value even when the animals remain healthy.

💡 Lighting

UVB is unnecessary. Give a dim 10-12-hour day-night rhythm and shaded retreats. Bright illumination keeps the colony hidden, while direct sun can overheat a small dark container very rapidly.

🌡 Heating and temperature

Maintain most of the enclosure at 23-28 °C with a small side zone of 28-30 °C. Leave a 21-24 °C retreat and allow nights down to 20-24 °C. Reproduction slows when the colony is cool, but keeping the entire box hot removes the animals’ ability to regulate themselves.

Heat the room or one side wall through a thermostat. Do not place an unregulated mat under the substrate: drying and overheating occur first where nymphs seek cover.

💧 Humidity and water

Keep one lower corner lightly moist while the opposite surface and bark dry between waterings. A working range of 50-70% RH is less useful than the visible gradient. Continuous condensation, a sour smell, or sluggish animals in wet leaf litter indicate too much water or too little air exchange.

Offer a very shallow textured water dish or an insect-safe drinking source. Fresh vegetables supply additional water, but should not be used to compensate for a completely dry molting refuge.

🌿 Enclosure and decoration

Use 5-8 cm of pesticide-free soil or coir mixed with crushed hardwood leaves and pieces of decayed hardwood. Lay cork bark at different angles and include narrow vertical crevices; adults use these surfaces for resting and molting. Secure heavy bark before adding the colony.

Avoid cedar and other resinous woods, fertilizer, perlite, sharp sand, and permanently saturated moss. Fine ventilation mesh must be fixed from the outside or protected, because gaps around glue and cable holes become escape routes.

🪳 Feeding

This is an omnivorous litter cockroach, not an assassin-bug predator. Keep hardwood leaf litter available. Offer a quality cockroach diet or grain-legume staple, and rotate carrot, squash, apple, pear, leafy greens, and a little pollen. A small portion of fish food or other moderate protein once weekly is enough for a growing colony.

Use two shallow feeding stations so shy animals can eat without piling up. Remove wet food within 24-48 hours. Excess animal protein and fruit left in a warm enclosure encourage mites, flies, mould, and reproductive setbacks.

🥚 Breeding

Females retract the ootheca and incubate it internally, then give birth to mobile nymphs; the metadata therefore uses “viviparous,” though keepers often say ovoviviparous. Captive observations commonly report roughly 10-18 nymphs per brood, but peer-reviewed line-level brood measurements are not available. Treat that number as a husbandry range rather than a species limit.

Stable warmth, several retreats, and a semi-moist—not saturated—substrate support reproduction. Colonies can pause after transport or after being kept too wet. Do not repeatedly dig for young; watch for feeding growth and cast skins instead.

🩺 Common problems

Unexplained reproductive pause: check persistent wetness, crowding, temperature, and whether both sexes are present before changing several parameters at once.
Failed molts: preserve a humid lower retreat and firm vertical surfaces while maintaining airflow.
Escapes: replace warped lids and coarse mesh; a petroleum barrier is only a backup, never the primary closure.
Mites or fungus gnats: reduce leftover moist food, remove corpses, and exchange the wettest substrate patch rather than sterilising the entire colony.
Allergy: cockroach frass and shed skins can irritate or sensitise airways. Dampen dusty waste, wear gloves, and use suitable respiratory protection if you are sensitive.

📌 Conclusion

P. formosana suits a keeper who wants an active patterned species and already has reliable micro-insect containment. Prepare the lid, fine mesh, moisture gradient, and catch tub before the colony arrives; correcting an escape-prone enclosure after opening the transport cup is too late.