Survey of necrophagous insects in the Nebraska Sandhills

Blow flies (Diptera: Calliphoridae) and beetles (e.g. Coleoptera: Silphidae, Staphylinidae) are an important part of terrestrial decomposition because of their ability to quickly locate and colonize carcasses. Their breakdown of carcasses allows nutrients to be released back into the environment, creating fertility islands that benefit soil, plant, and animal diversity. However, species colonize and consume carcasses at different rates and not all species are present throughout the year.

To better understand necrophagous blow fly and beetle populations, we conducted a survey in the Nebraska Sandhills in the Valentine National Wildlife Refuge, a mid- and tall grass prairie that covers approximately 100 square miles. A frozen/thawed rabbit (1-2 kg) was placed on the open ground. A cone trap was placed directly over the rabbit’s head. The trap and the rabbit were covered with a square of chicken wire staked in the ground to reduce large animal predation. Twenty traps were placed throughout the Refuge on a 32 km transect and were monitored and emptied every 12 hours for 72 hours. Three trapping periods were conducted in May, July, and September. Specimens were also collected with sweep nets from large mammalian and avian road kill found along the highway running through the Refuge. Adult Dipteran and Coleopteran specimens were identified using morphological characteristics.

The population dynamics of blow flies change throughout the seasons. In the Refuge, generally, Calliphorinae (blue bottles) were better represented in May and Lucilinae and Chrysomyinae were better represented in July and September. It was observed that highways may function as facilitators to insect movement due to the asphalt’s ability to retain temperature. On the highway, species abundance was higher and diversity lower, whereas .03 km off the highway, species abundance was lower and diversity higher. More intensive studies are needed to better understand how manmade structures can alter the insect biodiversity on grassland ecosystems and how those effects can change terrestrial decomposition.