Ecology of insect communities in nontidal wetlands.

Published research about wetland insects has proliferated, and a conceptual foundation about how wetland insect populations and communities are regulated is being built. Here we review and synthesize this new body of work. Our review begins with a summary of insect communities found in diverse wetland types, marshes, forested floodplains, and peatlands. Next, we critically discuss research on the population and community ecology of wetland insects, including the importance of colonization strategies and insect interactions with the physical environment, plants, predators, and competitors. Results from many of the experimental studies that we review indicate that some commonly held beliefs about wetland insect ecology require significant reevaluation. We then discuss the importance of wetland insect ecology for some applied concerns such as efforts to manage wetland insect resources as waterfowl food and development of ecologically sound strategies to control pest mosquitoes. We conclude with a discussion of wetland conservation, emphasizing insect aspects.

Efficacy of methoprene pellets against Coquillettidia perturbans larvae.

Of 21 wetlands in the Minneapolis-St. Paul area that supported similar densities of Coquillettidia perturbans larvae, 7 wetlands were treated with Altosid methoprene pellets at 5.6 kg/ha on May 28, 1992, 7 were treated with Altosid XR extended residual methoprene briquets at 1 briquet/9.3 m2 in March 1992, and the final 7 remained untreated. Emergence data collected from May 28 through late August in all sites indicated pellet and briquet treatments achieved greater than 90% control.

Technique for surveying larval populations of Coquillettidia perturbans.

A dipper with a 1-mm mesh screen bottom was used to sample larval populations of Coquillettidia perturbans from plant roots in Minnesota wetlands. This sampling technique was especially useful for large-scale larval surveys because the sampler was portable, individual sample collection and processing could be completed in < 10 min and data collected were appropriate for statistical analyses. Sampling indicated that larval populations were clumped, with a negative binomial model closely describing larval distributions.

Wetland management strategies that enhance waterfowl habitats can also control mosquitoes.

Two studies in California wetlands and a third in Minnesota wetlands indicate that management practices designed to enhance habitat quality for waterfowl can concurrently reduce mosquito problems. In a seasonally flooded pickleweed wetland in Suisun Marsh, Solano Co., CA, we demonstrated that reducing plant-cover by 50% increased benthic densities of chironomid midge and dytiscid beetle larvae; these insects can be important in waterfowl diets. This manipulation also concentrated Aedes melanimon and Culiseta inornata mosquito larvae along wetland perimeters; thus, the need for control measures was greatly restricted spatially. A study in 9 experimental ponds in Suisun Marsh demonstrated that higher water levels could enhance populations of the macroinvertebrates important in waterfowl diets; general macroinvertebrate densities were higher at 60 cm depths than 20 cm or 40 cm depths. In contrast, Cs. inornata densities were lowest at 60 cm depths and highest at 20 cm depths. A study conducted in a perennial-water cattail wetland in Minneapolis-St. Paul, MN, demonstrated that a temporary water-level drawdown, designed to enhance waterfowl habitat quality of perennial-water wetlands, also reduced densities of Coquillettidia perturbans mosquito larvae. These mosquitoes disappeared immediately after the drawdown, but even after water depths were restored to pre-drawdown levels, significant numbers did not reappear until 4 years post-drawdown. Studies in 202 other Minnesota wetlands also demonstrated the susceptibility of Cq. perturbans populations to drawdown, but the impact of drawdown was greater in stands of emergent cattail than in floating cattail.

Where is mosquito research published?

To identify the core journals that publish articles on mosquito research, the Agricola database (covering 1985-89 citations) was analyzed. This source contained 3,007 citations to mosquito research, and the citations were found in 404 different serials. Whereas 10 serials (2.5% of total serials) in Agricola produced 50% of the citations, almost one-half of the serials in this source contained only one citation to mosquito research. Fifteen journals (the core journals) contained greater than 1% of total citations. The number of citations found among 126 different databases and abstracting services that were examined varied: 39 had no citations to mosquitoes, but 13 (including life-sciences, medical and even popular-literature databases) had greater than 100 citations. The choice of core journals will be an increasingly important decision by biological libraries as costs for journal subscriptions rise.

Evaluation of methoprene, temephos and Bacillus thuringiensis var. israelensis against Coquillettidia perturbans larvae in Minnesota.

Temephos, Bacillus thuringiensis var. israelensis (B.t.i.) and methoprene were tested for larval control of Coquillettidia perturbans. Neither temephos nor B.t.i. treatments at their maximum recommended dosages consistently reduced larval numbers. Larval emergencies were reduced 99% in test plots treated with experimental, controlled release methoprene briquets (Altosid SR-10). Breeding sites of Cq. perturbans in a 5,000 km2 area were treated using methoprene briquets in the 1984 season. Adult populations in a 7,700 km2 area were 2.5 times higher in untreated areas than treated areas. Methoprene can effectively control larval populations of Cq. perturbans.