Posts Tagged ‘yellow fever’

Monstrous Clouds of Salt Marsh Mosquitoes (Aedes sp.)

October 2, 2011

Photo from google images of Aedes sollicitans, the common salt marsh mosquito.

Early colonists reported seeing clouds of salt marsh mosquitoes that would block out the sun.  European settlers may have enjoyed a bounty of fish, waterfowl, and game but life in the unspoiled wilderness had its drawbacks.  Salt marsh mosquitoes swarmed so ferociously that few American Indians chose to live on barrier islands.  The ones that lived there were likely forced to the seaside by bigger, stronger tribes they feared.  John Lawson, an early explorer of the Carolinas, settled inland too, specifically touting the benefits of fewer mosquitoes there than on the coast.

Even today despite well funded mosquito control programs, the number of salt marsh mosquitoes is astounding.  One square yard of salt marsh can produce one million mosquitoes.  Researchers can vacuum them off the marsh at a rate of 10,000 per minute.  Ocean breezes keep the blood-suckers off the beaches, but I well remember hurried walks on the boardwalks between the beach and a Harbor Island rental condo because of mosquitoes that lurked in the back dunes.

There are two species of salt marsh mosquito–the brown (or black) Aedes taenorhynchus and the common Aedes sollicitans.  Both lay their eggs in depressions or cracks in silt and detritus above the normal high tide line.  Their eggs can survive droughts for as long as six months.  They range along the coast from New England to Brazil, successfully occupying the extensive habitat for which they’re named.  Brown salt marsh mosquitoes don’t even need a blood meal to produce eggs.  If the larva of this species had a good supply of microscopic food (they eat bacteria, protozoa, rotifera, and fungal spores), the adult female can lay 25-75 eggs, though this number increases to 200 after a successful blood meal.  The other species of salt marsh mosquito does need a blood meal to produce eggs.

Salt marsh mosquitoes mostly feed at dawn and dusk.  They torment many animals including deer, rabbits, birds, alligators, crocodiles, sea turtles, and snakes.  Nocturnal raccoons usually avoid them because mosquitoes become less active at night.  Cooler temperatures slow them down, and hungry bats become active, so mosquitoes spend this time hiding in foilage.  Salt marsh mosquitoes harbor only one known parasite–dog heartworm.

During the Pleistocene salt marsh mosquito populations were likely highest during interglacials and interstadials which were characterized by warmer wetter climate and barrier island formation.  This led also to more salt marsh habitat.  Cool, dry, windy stadials undoubtedly diminished their numbers.  Mosquitoes don’t thrive in drought-like conditions, nor can they endure cold temperatures and high winds.  Yet, they did manage to survive Ice Ages–the coast remained warm enough.  Large mammals become immune to mosquito bites and won’t itch, though they do lose blood.  Thick-skinned beasts such as mammoths probably didn’t even notice mosquitoes after they’d developed this immunity.

There was no malaria or yellow fever in Pleistocene North America.  Malaria is caused by two species of plasmodium (a type of protozoa).  Several species of North American anopheline mosquitoes can host these parasites, but the parasites themselves didn’t live in North America.  Instead, infected Europeans and Africans carried the parasite in their blood when they came here and malaria spread when an infected human was bitten by a New World mosquito capable of hosting the parasite.  Yellow fever is spread by a frost intolerant invasive species–Aedes aegypti–which dies out during winter.  Yellow fever is caused by a virus carried by Aedes aegypti and was less common because frost wipes out this mosquito.

The Richmond County Mosquito Control Department is located 5 minutes from my house.  They waste a lot of pesticide.  I occasionally see them spray the sides of Piney Grove Road where the water never remains long enough for larva to survive.


A review of the New Television Series, Terra Nova.

Hey, Spielberg stole my idea, but instead of going back 36,000 years, he sent his fictional characters back 85 million years .  I was going to accuse him of stupidity–why would people want to go to the miserable climate of the Cretaceous when they could be living in the more familiar and comfortable Pleistocene?  But there is a plausible explanation–the crack in time leads to a wormhole that specifically goes to 85 million BP.

I’m going to accuse Spielberg of stupidity anyway, or at least of insulting people’s intelligence.  There were two scientific innacuracies in the pilot episode that I couldn’t stomach.  Sauropods were the first dinosaurs depicted on the show.  Sauropods were absent from the North American continent between 100 million and 70 million BP.  The shows producers don’t specify which continent this is all taking place on, but I bet, if asked, they would say North America.  They probably haven’t even though of it.  There is another inaccuracy that might not seem like a big deal to most, but it bothers me.  In the back ground there is grass.  Grass didn’t evolve until the Oligocene.  An accurate background scene would have a mixture of bare soil, a carpet of moss, and an open forest of conifers.

I might forgive these ignorant errors, if the show was entertaining but it’s not.  I could only endure the first 45 minutes.  When a rebellious teenage son refused to respect his, until recently, absent father–a very tired storyline already done 16,742 times on daytime soaps and family dramas–I gave up on this dreck.  What’s the show’s fatal flaw?  It’s boring.

Here’s a list of television shows I recommend instead–Outer Limits reruns (on Hulu and Chiller), Breaking Bad (on AMC), The Walking Dead (on AMC), Boardwalk Empire (on HBO),  Curb your Enthusiasm (on HBO), and Supernatural (on CW).