WHEN ARE MOST ACTIVE?

It’s easy to assume cockroaches are infesting our homes all year round. While the cooler months may offer some respite, entomologist Graeme Smith says cockroaches can invade kitchens and industrial spaces at any time of the year. That’s because they like warm and humid places no matter what the weather’s like. The warmer months are their chief breeding season, however, so it pays to understand their life cycle.

“When the weather gets cool, the cockroaches are much less active,” says Smith. “They almost go dormant, even though they don’t necessarily die out.”

Know your enemy

The movements of cockroaches can be broken down into the two main types of cockroaches encountered in this country:

German cockroaches

These small, brown cockroaches “are very prevalent in industrial situations like commercial kitchens and bakeries, on planes and trains, and things like that,” explains Smith.

If a dwelling or premises is heated and air-conditioned, the cockroach can be a year-round visitor — but will still be more common in summer. Their numbers also vary depending on location:

• Tasmania: Very few.
• Melbourne: Mainly in industrial sites and premises.
• Canberra: Mostly in commercial areas.
• Sydney: Grow more numerous around November; big numbers from January through to March, then a drop off in May through October.
• Queensland: Active for a much longer period; primarily September through May/June.

Larger American cockroaches

These larger cockroaches, like the Australian and smoky brown species, are more commonly found outdoors. They’re slower-breeding but — put down that sandwich if you’re going to read on — it’s worth knowing they like to breed in drains and occasionally in kitchens.

“Mostly they come into kitchens from outside, and they’re the ones that freak people out the most. They can fly as well,” says Smith.

As the weather warms up, they breed more and you’ll get more of them. “Up in Cairns they might be there almost the whole year round, but in the middle of winter they’ll drop off,” says Smith.