Why do mosquitoes seem more intense in northern climates?

When you think of mosquitoes, you typically think of warm muggy climates common in southern states.  But ask anyone north of Ohio and they will describe concentrated swarms of mosquitoes that would send even Lewis & Clark indoors. Intuition would tell you that since mosquitoes are rarely seen during the cold winters that most have probably been killed by snowy weather.  After all, we know these little nasty bloodsuckers as party crashers of warm summer barbecues.

Mosquito Curtains Inc. makes mosquito netting curtains as alternative to permanent screen porch enclosures.  They were surprised to find that sales were highest in northern states.  Based in Atlanta, they thought they lived in Mosquito-land, yet more than a half dozen northern states and Canada claim the mosquito as their state bird.  Owner, Kurt Jordan, searched for answers, "Sure there are factors such as architectural style, lifestyle, and potential snow damage to permanent screening; however, the intensity of mosquito concentrations in the north prompted us to speak to a few entomologists.”

Female mosquitoes drink blood because it contains certain proteins that enable it to lay eggs.  They are attracted to their hosts by light colors, body heat, humidity released during perspiration, and carbon dioxide.  While there are other chemical factors, the tastiest victims seem to be those with higher metabolisms or those exerting themselves outdoors.  Stand outside with a hoe in your hand and you wear a neon sign that says, “Dinner here.”

When the days shorten and temperatures drop, adult females and their larvae are able to enter a low metabolism stage called diapause.  During this phase, a gene switches the mosquito diet from blood to fats and sugars.  Mosquitoes in diapause will live in tree holes, basements, and many survive the winter in semi-hibernation.  Eggs will immediately become dormant and await the warmer season to develop. 

If conditions are just so, larvae will enter diapause sooner than the egg laying females and dormant eggs will accumulate.  And then comes the spring when mosquitoes awake from their winter sleep.

Snow melt provides prolonged saturation ideal for breeding.  Eggs that have accumulated during the fall season begin to hatch.  Invertebrate predators of the mosquito won’t awake for another month, and the first weeks of spring become the high season for mosquito nursery rhymes, free love and few predators to send them to mosquito heaven.

If you think that mosquitoes are killed by extreme temperatures, think again.  Mosquito species even live in Antarctica, though hibernate 11 months of the year. 

“Southern States have a longer persistent season,” says Jordan.  “The architecture and lifestyle has made permanent screening a more common norm.  Northerners take their short warm seasons more seriously and enjoy the outdoors while they can.  Architecture in the north seems to place more emphasis on the character of the porch over protection for a relatively short season and a removable screen enclosure seems to just fit."

###