Bugs on the bayou part three – mosquitoes

in Technical Issues by Admin — February 1, 2010 at 10:00 am | 2 comments

Editor’s note: I wrote this post because of my conviction that coastal insects have largely been ignored by systems ecologists, including the folks proposing serious ecological engineering throughout coastal Louisiana. Here’s a riddle: What’s black and slight and causes red all over? Answer: Tee-Maringuoin, Cher, the mosquito.

The importance of our small but ubiquitous insect cousins reflects their keystone role(s) in the coast, including; (1) converting massive quantities of plant carbohydrate into protein for higher level consumers; (2) recycling cellulose; (3) pollinating flowering plants; and (4) serving as vectors for pathogenic disease organisms.

This concluding piece on bugs on the bayou focuses largely on mosquitoes, a major insect player in roles 1 and 4. Mosquitoes probably serve to limit coastal development in terms of the annoyance factor but I doubt that this effect has been quantified for the gulf coast.

Mosquitoes

In part one of this post on coastal bugs I cited a book called What on Earth evolved? 100 species that changed the world, by Christopher Lloyd, who listed and ranked what he calls the 100 most important (groups) of species that ever evolved. Lloyd ranks humans at 6/100, mosquitoes at 14/100, ants at 25/100 and termites – not even in the top 100!

Based on ecosystem function I would rank the importance of both termites and ants within the top 15. As for mosquitoes, here are some quotes from Lloyd’s book that makes me wonder why he didn’t rank this group in the top ten:

Mosquitoes evolved at about the same time as the dinosaurs, 230 million years ago, and have probably had a bigger impact on vertebrate animals than any other living creature…mosquitoes are perfect vehicles for the transmission and replication of other types of parasitic life…About 300 diseases that affect humans are transmitted via mosquitoes…The most famous is Malaria.

The ongoing unspeakable suffering among the survivors in Port Au Prince provides at least a hint of what summertime life in New Orleans must have been like in the early 1800s. Back then, at least most NOLA residents had shelter, food, and water.

They also had heat and humidity and hordes of houseflies, attracted by the residue from horse drawn vehicles. They lacked storm drains, sewage treatment, window screens, ceiling fans, air conditioning, mosquito control and rudimentary medical care (including vaccines).

Here’s a short quiz on advances in the reduction of mosquito-related problems. Give yourself plus or minus one point for each correct/incorrect answer : (Correct answers at end of post).

1) Guess the date within five years when an American patent was issued for the first metallic mesh window screen designed to keep mosquitoes at bay. (Hint: it was post Civil War and pre-20th century);

2) Guess the date within five years for the first electric ceiling fans in the US. (Hint, it was also post Civil War and pre-20th century);

3) Guess the date within five years for the first commercially viable Yellow Fever vaccine. (Hint: it was post WWI and pre-WWII);

4) Guess the date within three years for the first commercial production of the insecticide Malathion in the US, used for topical control of household insects like roaches, flies and lice and broadcast for mosquito control. (Hint: it was five years prior to Little Richard’s Rock’n'Roll icon Tutti Frutti).

Perhaps no more dramatic symbol of the historic role of the mosquito in south Louisiana is an old church on N. Rampart Street in New Orleans. Our Lady of Guadalupe was built in 1826, specifically to officiate in the burial of enormous numbers of deaths resulting from yellow fever, a disease imported to the New World from Africa as a result of the slave trade, and primarily spread by the mosquito Aedes aegyptii.

Although Yellow Fever is no longer a problem in south Louisiana, West Nile Virus and other mosquito-borne human pathogens are still a concern, in addition to the general discomfort caused by bites from female mosquitoes (males suck sap, not blood).

It is said that cattle grazing in marshes in the Chenier Plain have suffocated from inhaling mosquitoes. Once in the mid seventies former LSU professors Jim Gosselink, the late Bill McIntyre and I landed in a helicopter on a beach ridge between Port Fourchon and Grand Isle. Our visit was extremely brief, however. I have never before or since encountered so many mosquitoes. Since that time I’ve wondered what specific conditions coincide to produce such a perfect storm of skeeters. This would seem like important coastal information worthy of investigation.

Traditional mosquito control

Attempts to reduce the public health risks of mosquito bites have largely involved physical (hydrologic) and chemical measures: wetland impoundment and draining (levees, canals and pumps); and insecticide spraying, either aerial or ground-based.

Readers over the age of fifty may remember the delightful experience of watching fireflies after sundown. I collected them in jars to light my bedroom. This is an experience largely forgotten as the result of the aerial dispersal of chemicals like Malathion for mosquito control – a practice that kills bees and other beneficial insects, as well as adult mosquitoes.

Wetland restoration for mosquito control

Restoration of Louisiana’s coast and specifically coastal wetlands became an official state goal in 1989. Since that time I’ve heard many, many arguments for restoring coastal wetlands but I’ve rarely if ever heard an explicit case made that mosquito populations could be reduced by bringing dying marshes back to life.

In 2003 I bought and had renovated a modest little town house in a 1982 vintage development called Port Louis on the North Shore of Lake Pontchartrain in St. Tammany Parish. This development was built at the edge of a 4,000 acre tract of dysfunctional coastal wetlands that had previously been “reclaimed,” impounded to support a failed agriculture enterprise.

Port Louis is presumably too remote to be covered by the St. Tammany mosquito control program, so mosquitoes and other sucking and biting insects are not uncommon during certain times and weather conditions. I suspect that the huge impounded tract that surrounds my place on three sides, with standing water in former baldcypress stands and intermittent ponds from rainfall, is worthless wetland habitat – but ideal breeding ground for mosquitoes. Restoration of this tract would provide significant habitat value to the North Shore as well as possible relief from mosquito bites and West Nile Fever concerns.

The most obvious way to begin the restoration of this tract would be to breach the old levees to reconnect the ecosystem to tidal exchange with the Lake Pontchartrain estuary. This would flush the area, promoting plant growth. Reconnection with the estuary could dramatically reduce local mosquito populations by allowing the ingress and egress of insectivorous fish from the lake.

I think that it’s high time to add mosquito control to the list of reasons for restoring wetland health. By the same token, levee projects designed to enclose freshwater wetlands may include the unanticipated consequence of higher mosquito populations.

References on mosquito control via marsh restoration include this from New Hampshire and this from Delaware. I also found a web site that specifically refers to mosquito control in St. Tammany Parish. The following quotes from that site are relevant:

Contrary to popular belief, healthy, functioning wetlands can actually reduce mosquito populations…Mosquito control programs commonly recommend that wetlands be drained in order to control mosquitoes. This is because mosquitoes require standing water to breed, and if there is no standing water, there will be no mosquitoes. Quite true. However, mosquitoes have a very short life cycle (from 4 days to a month), and their eggs can remain dormant for more than a year, hatching when flooded with water. Therefore, even after a wetland has been drained, it may still hold enough water after a rain to breed mosquitoes. The drained area may actually produce more mosquitoes than it did when it was a wetland!

Final thoughts about bugs on the bayou

On a unit weight basis the amount of food energy consumed by an animal is inversely proportional to its size. That’s because small animals – such as insects – have much more surface area than big ones. In other words, a ton of mice would consume considerably more grain per day than a ton of elephant.

The huge estimates of termite and ant biomass (see bugs on the bayou part two) are largely based on tropical regions. The Mississippi River delta with its rich organic soils may favor even higher population densities.

At any rate the combined biomass of ants and termites would seem to require an enormous demand for organic matter. This doesn’t include the voracious appetite of moth caterpillars that are ubiquitous. Thus a very significant portion of the gross primary production of coastal wetlands within the delta must be consumed annually by the combined hunger of insects of all types.

One more thought. I wonder how insects were affected by the recent cold snap in the southeastern US?

Len Bahr (len.bahr@gmail.om)

Answers to quiz: (1) Metallic screening used in screen doors and windows was patented (#297,382) on April 22, 1884 by John Golding of Chicago.

2) The electrically-powered ceiling fan was invented in 1882 by John Fany. Fany had engineered the electric motor used in the first Singer sewing machines, and in 1882 adapted that motor for use in a ceiling-mounted fan. “The Fany Electric Fan”, as it was known, operated like a common modern-day ceiling fan; each fan had its own self-contained motor unit, eliminating the need for costly and bulky belt systems.

3) In 1937, Max Theiler, working at the Rockefeller Foundation, developed a safe and highly efficacious vaccine for yellow fever that gives a ten-year or more immunity from the virus. For his work on the yellow fever vaccine, he received the 1951 Nobel Prize in Physiology or Medicine.

4) Malathion was first produced commercially in the US in 1950 by American Cyanamid. I was ten years old and still enjoyed catching fireflies after sundown, alas, no longer widely possible.