ideal pet and feeder
Gromphadorhina portentosa is a large (two and a half inch) stocky brown and black roach hailing from the island of Madagascar. It is the most common roach in the trade due to its appearance, large size, flightlessness, and ease of care. It is raised both as a pet and as food for larger animals, it also frequently shows up in film and television whenever the script calls for a cockroach. It should be noted that G. portentosa requires a warm, humid environment and is unable to infest structures like its American and German cousins, except in the extreme southern US. As a result, it has been banned from several states including Texas and Florida. Keepers in these states should be aware of this and take extreme measures to prevent escapes.
G. portentosa is a tropical animal. As such, it requires high humidity and temperatures. Keep the humidity at around 70-80% my misting as needed, usually daily. Temperature should be kept above 75°F and they will only breed at 80°F plus. I keep mine at 88°F and they do very well at that temperature. They start doing badly at temps above the low nineties, don't keep them that hot.
I keep mine on bark. I have also seen them kept on sphagnum, peat, coconut, and various mixtures of the above more or less sucessfully. Not too critical. They do not seem to burrow much, anything over and inch and a half is uneeded.
A 10 or 15 gallon aquarium or five gallon bucket (with modified lid ) will work well for a small (less than 15 adults ) colony. Use a large rubbermaid-type container (again, with modded lid) or large aquarium for larger colonies. Provide lots of egg carton or cork bark hiding spots. Stack them, they will climb.
Speaking of climbing, you need to find a way of keeping them from climbing up the glass and out of the cage. It's fairly easy to stop the adults, the nymphs are a different story. They can squeeze through impossibly small spaces, you can't plug them all. Smear an inch-thick band of petroleum jelly (vaseline) all around the inside of the enclosure about one to two inches from the top. Their feet can't adhere to the jelly (or they know the jelly will damage their feet and avoid it, I can't remember which. Either way, it still works). Make sure they can't use the hide structures as a bridge over the jelly.
They can consume more or less anything organic, however you still should provide a varied, high-protein diet. I give mine dry dog food, flake food meant for fish, lettuce, and carrot, all chopped or crushed into small pieces (or almost powder, in the case of the dog food). Most of your various table scraps (banana peels, apple cores, gristle, that sort of thing) should be usable. Remove all uneaten fresh food within a day or so, before it starts to rot.
A small water dish should be used. Be sure to stick a small chunk of cork bark in there, they will walk in and drown like crickets.
Mature G. portentosa are easy to sex, males have two horn-like protrusions on the top of the "head" (it's not, the real head is tucked under the body), that the females lack.
male top, female bottom
A ratio of one male to two females seems to work well, feel free to mess around with it.
The female will deposit an egg case (properly known as an ootheca) that will release twenty or so small nymphs.
four-week-old nymph crawling on my hand
The nymphs require all the things the adults do, care-wise. They reach maturity in around five to six months. The adults pretty much leave them alone, and exhibit no parental care behaviors.
Let me know if you see any inaccuracies of feel I left anything out.