for National Geographic News
Humans aren't the only ones to take a summer holiday, a new study has revealed.
Creepy-crawlies, flies, and plants also join the vacation rush by hitching long-haul rides inside airline baggage.
The research reveals that—as for people in many countries—June, July, and August are the peak months for long-distance travel.
Previous studies have shown that international flights are a significant factor in unwelcome insect invasion. Some 73 percent of recorded pest interceptions in the U.S., in fact, occur at airports. (Related: "It's Invaders vs. Invaders as Scientists Target Alien Species" [February 22, 2006].)
Curious to determine when insects pack their bags and where the bugs are most likely to go, Andrew Tatem and Simon Hay of the University of Oxford in England studied global flight patterns for the 12-month period from May 1, 2005 to April 30, 2006.
Pest transfer between far-flung locations is more likely when the weather is similar in both regions, making it easy for the pests to settle into their new home.
So the researchers used rainfall, temperature, and humidity data from each region to work out which places linked by the global flight network had the most similar climates at various times of the year.
"Hawaii, with its moderate year-round climate, is a hot spot for pest invasions," Tatem said. "It is linked to a similar climate in Central America in April, Asia in July, and the Caribbean in October."
In general, though, June, July, and August are the peak months for insect travel.
"There are more airports in the Northern Hemisphere, and the major Southern Hemisphere airports tend to be closer to the Equator," Tatem said. "The June-to-August period stood out as the time when, overall, the busiest flight routes connect geographically distant but climatically similar locations."
The new study appears in the Proceedings of the Royal Society B.
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