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New Mexico State University

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NMSU researchers study development of telltale insects in dead bodies

When a dead body is found, investigators can learn a lot by studying the presence of insects for clues about the time since death occurred. But insect activity varies from place to place due to temperature and other factors. A study by researchers at New Mexico State University is under way to learn more about the development of insects in these situations, with one goal being to provide helpful information to such investigations in southern New Mexico.

Scott Bundy, associate professor in New Mexico State University's Entomology, Plant Pathology and Weed Science Department, examines insects whose development can provide valuable clues about the time of death of an animal or person. (NMSU photo by Darrell J. Pehr)

The two-year project, which started in May 2005 at NMSU's Livestock Entomology Research Facility, used pig carcasses to examine insect activity hoping to learn "who are the important players when it comes to a dead body," said Scott Bundy, associate professor in NMSU's Department of Entomology, Plant Pathology and Weed Science. "What insects are they? When do they show up? My interest was: What's the biology of the insect?"

The pig carcasses were placed in three environments: full shade, partial shade and full sun. The carcasses were placed in metal mesh enclosures to protect them from interference from other scavengers, such as coyotes, badgers, skunks, bobcats, mountain lions, buzzards and crows. Careful measurements were made every hour of the temperature inside the pigs as well as the soil and air using automatic data loggers and internal probes. Samples of insect activity were taken every day for the first 20 days, then at longer intervals over the next several months as insect activity declined.

Researchers recorded the position and type of insects present on sampling days. Adult and larval specimens were collected from each pig and identified in the lab. Researchers also noted how long each carcass remained in the various stages of decay.

First to arrive at the bodies were ants, which fed on fresh blood. Next came flies, some within the first 15 minutes. Beetles began to arrive at the carcasses from three to seven days after death.

The study was repeated during the summer of 2006. Working with Bundy on the project are researchers whose main responsibilities lie elsewhere, but who squeezed into their schedules the time it has taken to conduct this important research. Bundy, for example, specializes in the insect pests of cotton and alfalfa, and he has a particular interest in stink bugs and assassin bugs.

Others working with Bundy on the research project are undergraduate student Sean M. O'Donnell; NMSU Extension Plant Sciences Department Head Ron L. Byford; and Matt Lee, who earned his master's degree from the EPPWS Department at NMSU and now works in the private sector.

Bundy said student interest in the project is generally keen at first, especially in light of popular television shows that dramatize the work of forensic scientists. That interest tends to wane when the reality of the subject matter settles in.

"They watch 'CSI' and want to be forensic entomologists," Bundy said. "It's not quite as Hollywood as we see on TV." Bundy has presented the findings as a guest lecturer in entomology classes, but the topic is not part of the regular curriculum.

Now that the field work is complete, researchers will examine the specimens they collected, focusing on key species, especially the secondary screwworm fly. They will look through their temperature data to help determine development time of the insects under different conditions. Ultimately, the researchers intend to publish their findings in an article for a journal of forensic science.