They suck your blood and buzz annoyingly around your ears. Their itchy bites can turn a festive barbecue miserable or ruin a bucolic walk in the woods. The most baneful ones spread diseases.

In almost every country in the world, mosquitoes are a menace.

Everywhere but Iceland, that is.

Iceland is one of the few habitable places on the planet that is mosquito-free, and nobody really seems to know why.

It’s not nearly as cold as Antarctica, which is so frigid that mosquitoes (and people, for that matter) could never survive exposure to the elements there for long. Nor does Iceland lack the ponds and lakes where mosquitoes love to breed. And the insects are able to thrive in Iceland’s neighbors — Norway, Denmark, Scotland, even Greenland — which only adds to the mystery.

The most likely theory proffered so far, scientists say, is that Iceland’s oceanic climate keeps them at bay. When mosquitoes lay eggs in cold weather, the larvae emerge with a thaw, allowing them to breed and multiply. Iceland, however, typically has three major freezes and thaws a year, creating conditions that may be too unstable for the insect’s survival.