The shadow cockroach, Pycnoscelus nigra, is a glossy black, red-legged burrowing roach from tropical and subtropical Asia, 20 to 24mm long as an adult. Its care comes down to a handful of things: 24 to 28°C, 60 to 80% humidity, a deep soil-based substrate that is damp underneath and drier on top, leaf litter and rotting wood as the staple food, and a lid that seals, because adults climb. It is easy to keep and hard to watch, because it lives and breeds underground. Like every hobby culture keepers have reported, our captive-bred shadow cockroaches are all female, so a small group is a whole colony.
What the shadow cockroach is
Brunner von Wattenwyl described the species in 1865 as Panchlora nigra, and the name simply means black. You will also see it written Pycnoscelus niger, the spelling the Cockroach Species File uses, while the 2025 revision of the genus keeps nigra. It belongs to the family Blaberidae, in a genus of 18 named species, counting the two described in 2025, most of them native from India across to China and South East Asia. "Shadow cockroach" and "shadow roach" are trade names. We have found no common name for it in the scientific literature.
Size and colour
The 2025 revision measured wild specimens from China at 20.3 to 24.1mm for females and 19.5 to 23.8mm for males, wings included. Adults are shiny black with full-length wings, and the pronotum, the shield behind the head, carries only a narrow yellow area at its front corners. Keepers describe the legs as red, and on our stock they run red-orange, the quickest thing to look for against the black body.
Where it comes from
The records are overwhelmingly Asian. Of the 87 occurrence records on the Global Biodiversity Information Facility at the time of writing, 49 are from China and 15 from Thailand, with most of the rest from elsewhere in South, South East and East Asia. The specimens examined in 2025 came from five Chinese provinces and municipalities, from 275m on Hainan up to 1,400 to 1,900m in western Yunnan. There are no Australian records. No published locality exists for the stock in the trade.
Shadow cockroach or Surinam cockroach?
The Surinam cockroach, Pycnoscelus surinamensis, has spread with plants through the tropics worldwide, where it is a plantation and garden pest, and further north it turns up in heated greenhouses. It is not a common household pest, and in Britain it is recorded only occasionally, arriving with houseplants. We have found no pest record for P. nigra anywhere.
Colour alone will not separate them. Keepers describe the shadow roach as black and the Surinam as brown, but published descriptions put the Surinam at brown to black, and one US keeper has reported stock sold as P. nigra that turned out to be a dark strain of the Surinam. Their sizes overlap almost entirely. Check these instead:
- The pronotum. The Surinam has a pale band along the whole front edge. The shadow roach has only a narrow yellow area at the two front corners.
- The legs. Keepers use the red legs of the shadow roach as the quick check against the Surinam.
Keep one species per tub. One keeper who has run both reports the Surinam growing almost twice as fast, so in a mixed tub it can end up as most of the colony.
Setting up a shadow cockroach tub
A ventilated plastic tub is all a starter group needs. Lay the substrate at least 5cm deep, and deep enough that an adult can bury itself with room to spare underneath. Depth gives you a damp lower layer under a drier top, so the colony can choose its own moisture. Bark slabs laid flat on the surface give cover to anything that comes up.
Adults and larger nymphs climb smooth plastic and glass, so the lid has to seal, and any vent needs fine mesh: newborn nymphs of the Surinam relative measure only about 4.5mm. A barrier band around the inside of the rim is a sensible second line of defence. Ventilation should be moderate: enough to stop the air going stale, not so much that the top layer dries out in a day.
Temperature and humidity
Shadow roaches do best at 24 to 28°C, and the warm end gives the fastest growth. We have found no measured tolerance range for this species, so treat that band as the target rather than the edge of what it survives. English homes average about 19.0°C through the heating season, October to April, and 18.1°C in December, so through the colder months a heat mat on a thermostat earns its place. Fix it to the side of the tub, never underneath: a mat under the tub heats exactly the layer the burrowing adults and nymphs retreat into.
In summer a typical English home, about 21.5°C in July and August, keeps them going with no heat mat, though they grow and breed more slowly. If you leave the mat on, keep the warm end in the high twenties and below 30°C, and turn it down in a heatwave. Overheating costs you young: a 1940 study recorded overheated Surinam roach females aborting their egg cases.
Humidity belongs in the 60 to 80% band, but you do not need a hygrometer to manage it. Keep part of the substrate damp to the touch, leave the rest drier, and the colony will sit where it wants. If a colony goes quiet, check the moisture. One keeper with a struggling Surinam colony reported it becoming more active and eating leaves again after the substrate was made a little wetter and lettuce was added.
Substrate and diet
The substrate is also the food. Coir or organic topsoil makes a fine base for a roach tub. Coir holds moisture but is not food, so mix in fermented flake soil and shredded rotten wood, then work mixed broadleaf leaf litter through it and lay more over the top. Top the litter up before it is eaten down to bare soil.
Leaf litter and rotting wood are the staple, and everything else is extra. Offer vegetables and a little fruit, with a dried protein such as fish flake or dog biscuit twice a week, and take out anything that starts to mould. Leave a piece of cuttlebone or some crushed limestone in the tub permanently.
Breeding: a colony with no males
As far as anyone has reported, every shadow cockroach in the hobby is female, and the females breed without a mate. Keepers have not seen males or mating in their cultures, and our stock is the same. That is a fact about the hobby rather than the species: the 2025 revision examined 15 wild males alongside six females from China, so bisexual populations exist in the wild. What reached the hobby appears to be an all-female line, which means nothing to sex and no ratio to get right. A single adult can start a colony.
Like the Surinam roach and the rest of its family, the shadow roach is a live-bearer. The female forms an egg case, draws it back inside her body and carries it until the nymphs hatch, so in a healthy colony you will not find egg cases lying in the substrate. We have found no published litter size for this species. For comparison, University of Florida figures give the Surinam roach about 26 eggs per case, about three cases in a lifetime and 160 to 220 days to adulthood.
Give a new colony time: numbers build out of sight, and one keeper wrote that theirs had "exploded". Digging through the tub to look for nymphs breaks up burrows and tells you very little.
Behaviour and handling
This is a burrower first. Adults and nymphs spend most of the day under the substrate, so a tub can look nearly empty when it is full. If you want roaches on show, it is the wrong choice. To move some, scoop them up with a handful of substrate rather than chasing individuals across the surface.
Adults have full-length wings, but we have found no report of a shadow roach flying. The evidence on its relative is mixed: published work calls both sexes of the Surinam roach poor fliers, one US seller says it cannot fly, and one keeper describes theirs jumping and fluttering. Treat the shadow roach as a climber that may flutter, and keep the lid on.
Frequently Asked Questions
Do shadow cockroaches need a male to breed?
No. As far as keepers have reported, hobby cultures are all female and the females produce young without mating, so one adult can found a colony. Wild males exist in China, but none are known in captive stock.
Is the shadow cockroach the same as the Surinam cockroach?
No. They are separate species in the genus Pycnoscelus. The shadow roach has red legs and only narrow yellow corners on the pronotum, where the Surinam has a pale band across the whole front edge.
Can shadow cockroaches climb or fly?
Adults and larger nymphs climb smooth surfaces, so the lid must seal. We have found no report of one flying, though its winged relative is described as a poor flier rather than a non-flier.
Will shadow cockroaches infest my house?
Unlikely: we have found no pest record for this species. Hobby stock breeds without males, though, so a single escapee could start again in the soil of a pot plant, the route by which the Surinam roach reaches British homes. Keep the tub well away from houseplants and greenhouse plants. Section 14 of the Wildlife and Countryside Act 1981 makes it an offence to release a non-native animal or let one escape into the wild, so keep the lid shut and never release them.
How big do shadow cockroaches get?
Adults measure 20 to 24mm including the wings, and males and females overlap in size.
Do shadow cockroaches need a heat mat?
Through the colder months, yes, because English homes average about 19.0°C in the heating season, below their 24 to 28°C band. Fit the mat to the side of the tub on a thermostat, never underneath.
Where to go from here
The shadow roach suits a keeper who wants a colony that looks after itself. For another burrower kept damp below and dry on top, read our Domino cockroach care guide. Our guide to the best pet cockroaches for beginners compares the options, and the full range is in our cockroach collection.
If you would rather have a roach you can watch and pick up, the Madagascar hissing cockroach is the starter I point most people at, and the Madagascar hissing cockroach care guide covers everything it needs.
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