Minimizing the Effect of Roads on Aquatic Insects by Development of "Dragonfly-Friendly" Pavements

Focus Area

Wildlife & Ecosystems


Natural Resources






2-3 years

Research Idea Scope

Aquatic insects such as dragonflies, damselflies, and mayflies use horizontally polarized light as a cue to detect water where they lay their eggs. It is crucial that these insects lay their eggs directly in water or at the water’s edge. Eggs not deposited in water die. Paved roads reflect horizontally polarized light similarly to natural water bodies, which deceives aquatic insects. Roads become an ecological trap where aquatic insects lay their eggs on paved roads instead of in water. Paved roads often reflect horizontally polarized light more intensely than water, meaning that the roads are ecological traps that cause decreased insect reproductive output. The environmental cue emitted by the ecological trap (paved roads) exploits an evolutionary preference for water by these insects to the extent that paved roads may be chosen over water. Two groups of insects that rely on water are dragonflies and damselflies (odonates). These groups are particularly vulnerable to roads because adults are struck and killed by vehicles that use the roads, and because odonates all must lay their eggs in or near water.

 Odonates are a charismatic group of insects that play important roles in the ecosystems in which they live. They are efficient predators and help control populations of nuisance insects such as disease-carrying mosquitoes and biting flies. Paved roads are particularly efficient traps of odonates. However, paved roads are not all the same. Asphalt cement pavements and concrete pavements may be formulated with different aggregates and/or binders. These formulations have very different optical properties that generally result in asphalt cement pavements being darker and concrete pavements lighter. Intuitively, horizontally reflected polarized light should be reflected differently from these pavements, but the idea has not been tested.

Our two objectives are1) to evaluate the horizontally polarized light-reflecting properties of a series of road surfaces including asphalt cement pavements and concrete pavements; and 2) to quantitatively assess the attractiveness of high and low reflecting pavements to odonates. Our goal is to develop an environmentally "friendly" pavement that will be less likely to act as an ecological trap for aquatic insects. These data will allow state DOTs to select the most environmentally benign pavements for use in sensitive wetland areas where odonates lay eggs.

Urgency and Payoff

State DOTs will directly benefit from this research because it will provide quantitative data on the effects of a suite of pavement formulations. As a group, odonates are important predators and help control populations of nuisance insects such as disease-carrying mosquitoes and biting flies. This extremely charismatic group is experiencing an increased awareness and demand for protection by the general public, which may be assuaged by use of dragonfly "friendly" pavements. This research will fulfill a pressing need to determine the extent and causes of ecological damage to an array of odonate species and their habitats associated with our road systems, particularly those in the Upper Midwestern United States. This region is home to a federally endangered dragonfly, Hine’s emerald (Somatochlora hinea). Globally, 300 species of odonates (IUCN-World Conservation Union Red List of Threatened Species) may be affected by polarized light reflected from pavements. The research has implications that extend to the protection of waterfowl such as the common loon, which also uses horizontally polarized light as a cue for water in which to land. Loons deceived into landing on pavement can break their legs, which results in death.

Suggested By

Jacqualine Grant, Michigan Technological University, Telephone: (906) 487-1093

[email protected]