Sapphire Flower Cockroach, Eucorydia yasumatsui

Metallic sapphire wing cases over a body flashed with orange, on an animal small enough to sit comfortably on a fingernail. Show somebody a photograph of an adult Eucorydia yasumatsui without telling them what it is and most will guess a jewel beetle. Almost nobody guesses cockroach, and that reaction is a fair part of why this species has the reputation it does.

Now the honest caveat, because it belongs at the top rather than buried near the bottom. The blue only arrives at the final moult. Nymphs are plain, dark and unremarkable, and if you buy them as nymphs you are buying a promise that takes months to be delivered on. Plenty of people find the wait to be the best part of keeping them; some do not, and it is better to know before ordering than after.

The species

Eucorydia yasumatsui was described by Asahina in 1971 from the Ryukyu Islands, and hobby stock traces back to Iriomote in the far south of that chain. It sits in the family Corydiidae, the group generally known as flower roaches, which is where the common names come from: Sapphire Flower Cockroach, Sapphire Cockroach, or simply Eucorydia.

Adults are small, in the region of 10 mm, so this is a species you keep in a display enclosure and look at closely rather than one that fills a tank. Males and females both carry the colour.

The one thing that kills them

Ventilation, and it is not a marginal preference. Experienced keepers have lost entire colonies of nymphs over a matter of months to nothing more than a poorly ventilated tub, and this is by a wide margin the most common way people fail with the genus.

Run them noticeably drier and airier than instinct suggests for something from subtropical Japan. Good airflow across the whole enclosure, a substrate that is damp rather than wet, and one area kept moister than the rest so they can choose. A sealed box with high humidity is the exact opposite of what they want, and it will not show as a problem until it is already too late to correct.

Setting up

Deep substrate is the second requirement, since nymphs live buried in leaf litter and humus and spend most of their long development out of sight. Lay 7 to 10 cm of a nutritious forest-floor base such as our invertebrate substrate and cover it thickly with hardwood leaf litter, because that litter is both their habitat and the bulk of their diet. Magnolia leaves work well and last.

Add cork bark for surface cover and keep the enclosure warm. One practical note worth planning around: nymphs cannot climb smooth surfaces, but adults can, so an enclosure that safely held a group of nymphs may not hold the same animals once they mature. Check the lid before the first ones turn blue.

Seeding with a springtail culture is worth doing, since a deep leaf litter layer with occasional soft food is exactly where mould starts.

Feeding

Decaying leaf litter forms the base and should always be present. Beyond that they have modest appetites and are easy to overfeed: a little bee pollen, a small piece of soft fruit, or a pinch of fish food once a week is plenty. Take out whatever is left the following day rather than letting it sit in a warm enclosure.

The small appetite catches people out, because there is a temptation to keep adding food when nothing appears to be eating it. Resist it. Uneaten food in a Eucorydia enclosure is a mould problem waiting to happen, and mould in a poorly ventilated tub is how colonies are lost.

The timeline

This is a slow, patient species and the arithmetic is worth understanding before you commit. Nymphs take many months to work through their instars, with something in the region of half a year to reach pre-adult, and the adult stage that follows is short: a few months at most, and often less for males.

So the great majority of a Eucorydia's life is spent as a drab nymph underground, and the spectacular part is brief. Keeping them long term means running a colony with overlapping generations rather than admiring the animals you bought, and a group of mixed-size nymphs is the sensible way to start. Sexing them is not practical, so buy numbers rather than pairs.

Who this suits

Intermediate to advanced keepers, and specifically patient ones. There is nothing technically difficult here, no heating rig or specialist equipment, but the combination of a long wait, a short payoff and an unforgiving ventilation requirement means this is not a first roach.

If you want something spectacular sooner, the Emerald Cockroach delivers metallic colour with a gentler learning curve, and the Madagascar Hisser is the classic hardy starter. If you already keep Eucorydia and want a second species, the Giant Flower Cockroach is a larger relative with much the same husbandry.

Browse the full cockroach collection, or the wider other inverts range for the rest of the unusual end of what we keep.

Arriving with you

Captive-bred and sent Monday to Thursday only, by Royal Mail next day by 1pm, so nothing sits in a depot over a weekend. Animals travel in ventilated tubs with damp sphagnum moss inside a double-walled box, with a 20% overcount and our live arrival guarantee. Have the enclosure built and settled beforehand, and expect nymphs to bury themselves within minutes of going in and stay there. That is normal, and resisting the urge to dig them up is most of the skill with this species.