Before the Florda National Parks Association (FNPA) there was the Everglades Natural History Assocation (ENHA). The ENHA started a monthly newsletter in January 1962, with the goal of “revitalizing the Association membership and providing regular contact with the members.” The newsletter took on the name of “The Anhinga” in May 1963. The newsletter covered park programs, association events, and “occurrences and data of natural history significance.”
This article, written 60 years ago, highlights how drought conditions in the park can contribute to increased mosquito activity.
Six decades later, drought has once again made for a particularly buggy start to the wet season here in the Everglades. According to Drought.gov, 2025 ranks as the 21st driest year to date (January–June) out of the past 131 years.
A FINE MOSQUITO YEAR
Editor – Gale Koschmann Zimmer Written by – Ernst Christensen
Nowadays whenever Park personnel engage in casual conversation the subject is mosquitoes. This is one of those bad mosquito years — and almost any old timer could have told you it would be.
The current three-year draught and the Park’s water shortage has much to do with it. But so does the pattern of this year’s rainfall.
The prolonged draught and the drying up of most of the waterholes of course resulted in the dying off of most of the mosquito fish. Certainly, the populations of gambusia, mollies, and top minnows are probably at an all-time low. These prodigious eaters of mosquito larvae are confined to a few isolated water pools. The water level in the park has not yet become high enough to flood the sawgrass areas. Thus, the aquatic life has not been able to disperse. Samples recently scooped from culverts and portions of the Taylor River area (Taylor slough) contained only such things as small crayfish, polliwogs, ostracods and other minutia. Not a single fish was included in the samples taken from these waters. Thus, the mosquitoes using such ponds for breeding have little natural control.
Not all of the Park’s many species of mosquitoes lay their eggs on the surface of pond waters. Almost each species has its own individual technique. Some, of course, simply lay their eggs on the surface of any still pond. They subsequently hatch to become the well-known “wigglers” in the pond. But other mosquitoes lay their eggs on grass stems that await the advent of rising water to hatch them. Still others lay their eggs in the mud above the water line so that either unusually high tide or flooding by summer rains will hatch their eggs.
Now you see how draught situations produce bad mosquito years. Low water levels expose large areas of mud and grass stems for When the rains do come to inundate the eggs, a huge brood of mosquitoes result. Now when the rains are intermittent as they have been this year, the water level drops enough after each rainy spell to expose the mud banks and grass stems for the new brood to lay their eggs. Then the rains come back and a second much larger brood results.
Usually, gambusia fish and other natural enemies of the mosquito multiply apace and gobble up the horde of new larvae — eventually so completely that most of the mosquitoes disappear.
But this year, for the present at least, we do not have the abundance of little fish that are needed and so the mosquito situation in the park is rather grim. Artificial mosquito control is neither practical nor desirable — could in fact be dangerous to the Park’s ecology.
Considerable study is being made of the mosquitoes of the park especially by the Public Health Service. They are, for example, doing an inventory of the species of mosquitoes and are carefully testing disease carrying species for infections. They have been trapping and studying the mosquitoes of the Park for quite a while. Former traps used a light to attract the insects but a new technique using dry ice is far more effective. Apparent- ly it isn’t the mammal smell or heat that attracts the mosquito but the CO2 that is exhaled. This new trap contains a small piece of dry ice that is allowed to melt slowly, thereby diffusing CO2 to attract the mosquitoes. The results have been remarkable. A catch of from 500 to 600 in one night was considered a good one. On one recent night near Snake Bight a CO2 trap caught an estimated 12,000 insects! (Maybe we should install these things on the park trails?)
One thing for certain, an hour in an area loaded with mosquitoes will stimulate all kinds of ideas about how to get rid of them. Recently our attention was directed to an article about the effect of a strobe flash on mosquitoes. According to this author one flash would sterilize mosquitoes and two flashes would kill them. so, of course, we experimented. We flashed the strobe not twice but a dozen times with no result at all except getting covered with hungry and very live mosquitoes. Maybe the strobe light works only on the males?
The Anhinga newsletter is still going strong, now in digital form! Stay up to date with the latest park events, stories from our naturalists, updates from our institutes @evergladesinstitute @biscaynenationalparkinstitute and more!
