Roaches that pass in the night

Can cockroach species co-exist?

Pest management industry wisdom says that the UK’s cockroaches are pretty unsociable, preferring not to mix with other cockroach species. And when they do, the dominant German cockroach (Blatella germanica) quickly overcomes the more passive, smaller and slower-breeding species such as the Oriental cockroach (B. orientalis).

So when a meat retail outlet had a significant roach problem, with sticky traps filling up overnight with both oriental and German roaches, the technician called the BPCA  office for advice.

We advised that, while roach species mixed together in labs will quickly be dominated by B. germanica, in the real world, things are a bit different. B. orientalis may live in a sub-floor void or in a wall, while B. germanica prefers warmer spots like fridge motors or ovens. Then, in the dark of the night, both species are likely coming onto the shop floor to feed, thus the mixed catch on the sticky boards. One caveat; large populations of roaches may well throw out a signficant colour variation, which to the untrained eye might appear to be a different species. In this case however it was clearly two different species that had met a sticky end together.

So the next time your catch traps show a mix of roaches, don’t think they are ganging up on you – it’s just ships that pass in the night.


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