Bug Outbreaks Mostly Not Due to Warming

From a ship overrun with spiders to bedbug infestations at major clothing stores, is this the time of plagues?

THE GIST

- Infestations of bedbugs, ants and spiders have recently been reported.

- Bedbugs are returning to the U.S. because of the phase-out of DDT and their reintroduction from travel.

- Changes in climate are driving some insect populations to surge, spread or change.

Recent headlines have reported bedbugs in Manhattan outlets of Victoria's Secret and Abercrombie and Fitch, a boat from Guam that was turned away from port because it was swarming with thousands of non-native spiders, and a bumper year for ants in the nation's capitol.

Do these infestations of crawlies have any connection, like the super-warm weather this season or the long-term warming of our climate?

Not much, say experts, although climate is driving certain insect population changes.

One of the three recently reported "plagues" -- D.C.'s particularly pesky ants this summer -- may be caused by weather. An early warm spring followed by cooler weather allowed plants to thrive, said University of Maryland entomologist Michael Raupp, creating ideal conditions for aphids and other small insects that ants feed on to boom. This in turn allowed the ants to multiply beyond their usual numbers, creating a nuisance in many people's kitchens.

But Michael Potter, an entomologist at the University of Kentucky noted that the rise in ant numbers may be more complicated. "Ant problems have been building for more than a decade for reasons we don't really understand, and odorous house ants are particularly widespread."

Other insect populations are being affected by weather conditions this year. "We know that certain conditions are perfect for certain types of insects. We have mythical population sizes for mosquitoes this year," entomologist Lynn Kimsey of the University of California, Davis told Discovery News. "We had a long, cool wet spring. "

Long-term climate change -- mostly warmer conditions -- is allowing some insect populations to expand their range or develop faster, Rauss said.

"We are pretty convinced that we are starting to see a seasonal shift in the occurrence of pests. I saw lightning bugs earlier than I've ever seen lightning bugs emerge this summer. A colleague of mine at Ohio State is convinced that the vine weevil is emerging a week or two weeks earlier than earlier in our careers. We're seeing a seasonal shift as heat accumulates earlier."

Because insects are cold-blooded, Raupp said, temperatures drive their development. "As climate warms, animals that rely on temperature will emerge earlier and they will develop quicker."

The recent spider and bedbug infestations in the news are not related to climate, experts said. Rather, both are consequences of increased global travel and trade, which is also driving insect dynamics worldwide.

Infestations on ships are frequent occurrences that only occasionally get reported, experts said.

"I don't think it's unusual to have a lot of spiders on a ship as long as there is plenty of prey" Raupp said. "Spider populations are driven by the availability of prey."

Kimsey agreed, noting that she was once involved in the turning back of a ship at the Long Beach port that was "literally covered" with Asian gypsy moths, a species with the potential to decimate the U.S. landscape if it becomes established here.

Bedbugs, meanwhile, were once commonplace in the United States, but DDT all but wiped them out. DDT was a long-lasting pesticide that lingered on surfaces for the bedbugs to encounter when they snuck out of their hiding places.

International travel has brought bedbugs hitchhiking back to the United States, where they're eagerly filling their niche again, returning to hotels, homes and even hospitals, banks -- and lingerie stores.

"It's not a pretty picture," Potter said, "but it's not surprising."