Perspectives Online

4-H Forensics. Young sleuths solve the mystery of the postmortem interval - with help from Crime Solving Insects. By Terri Leith


Entomologist Steve Bambara sizes pipe cleaners in the proper maggot proportions to simulate the biological activity in a decomposing corpse.
Photo by Daniel Kim

The electronic booklet's "cover" has a teaser that would do Agatha Christie proud:

The horses in the pasture fidgeted with anticipation when they heard Mr. Johnson's lawn mower nearby. Little did anyone know that soon one of them would end up dead as a result.

Within a few pages, readers are invited to solve the mystery of a horse's death by studying the decomposition and insect activity in its corpse.

All that's missing is a background vocal of "Who-o-o are you?" The theme of the TV series "CSI: Crime Scene Investigation" could easily be soundtrack for another "CSI" - "Crime Solving Insects." That's the name of a new 4-H entomology curriculum.

Created for youths ages 13 to 17, it's a hands-on lesson in which 4-H'ers evaluate evidence from four animal death scenarios. The teens are given information about the life cycles of insects as related to the stages of corpse decomposition. Then they receive samples of simulated maggots "collected" from a fictional animal corpse and are asked to determine the postmortem interval in which the insects developed. The students are challenged to determine time of death and whether foul play was involved.


A much-magnified blow fly is the creepy cover image of the 4-H CSI curriculum co-authored by entomologist Steve Bambara.
Photo by Joseph Berger, www.forestryimages.com
In the process of solving these mysteries (and learning fascinating forensic entomology lessons), 4-H'ers are mastering skills such as critical thinking, problem solving, teamwork, communicating - learning to learn. At the same time they can appreciate the practical application of entomology in society and basically learn the concept of the "succession" of insect life and the role of decomposition in that succession.

The curriculum, available online for free download since January, was co-authored by Steve Bambara, entomology Extension specialist in the College of Agriculture and Life Sciences, and Dr. Lisa Carloye, formerly of Elon University and now at Washington State University. Carloye published an original version of the activity, "Of Maggots and Murder," in 2003 and has used that version - featuring human death scenarios - in teaching introductory biology classes. It has also been used in N.C.State biology class activities, said Bambara, who designed the 4-H publication and added the graphics.

In adapting Carloye's curriculum for use by 4-H'ers and 4-H volunteers, Bambara replaced human death scenarios with animal death scenarios.

"This was designed for teens, to be used with an adult leader who may not have any entomology training," said Bambara, whose areas of Extension responsibility include landscape, small grain and forage crop insects. 4-H is Extension's youth development program.


The when and why of mysterious animal deaths are solved with the help of "Crime Solving Insects," a 4-H youth curriculum co-authored by Extension entomologist Steve Bambara.
Photo by Daniel Kim
Producing the activity, he said, "was fun, but also a lot of work. I had to develop animal death scenarios that might be suspicious and also relate to the varied life cycles of fly larvae developmental stages."

In the case of the mysteriously deceased horse, the mode of death is one so subtle that the clues lie as surely in the size of the maggots upon the body as in the contents of the animal's stomach. But to deduce this, the student must apply provided information about the biological basics of corpse decomposition, the entomological basics of maggot growth and even some pharmacological facts about how the introduction of outside substances (drugs? naturally occurring chemicals?) may just alter things. All told, the insect activity should reveal time of death and if there was foul play.

That case is one of four available for solving. The 4-H'ers also can tackle the case of the female deer, found dead in Charlotte with no apparent wounds to its body. Given the recent daytime temperatures and the fact that maggots of different ages are in the body, the young investigators must determine time of death according to the entomological clues.

In the remaining scenarios, the insects recovered from the corpses of a pot-bellied pig and a pitbull terrier - coupled with the animals' locations - offer the essential clues.

By the time they're done, the 4-H sleuths will know what killed those animals and when. They'll also know a lot about the house fly, the blow fly, the flesh fly, the skipper fly and the other species of pupae that feed on a carcass - not to mention the predatory wasps and beetles that arrive at some point to feed on the fly maggots that are feeding on the corpse.

"There is also an additional optional activity where 4-H'ers can examine what happens to a [decomposing] chicken gizzard over several days and record their observations," Bambara said.

The scenarios are intended for the teens to examine in pairs or small groups, he explains. "Each takes about 20 minutes. An adult leader directs the activities. They need not all be completed in the same session. In addition, different color pipe cleaners are substituted for real maggots, so the activity may be conducted anywhere and at any time of year."

There is no completion requirement or any grade for the activity, he said. "The teens collect data and suggest an explanation. The discussion questions from the leader are designed to make 4-H'ers think. Each 4-H'er is different and will take away different things from the experience."

"Crime Solving Insects" is currently free for use for nonprofit educational purposes. Available online at http://www.nc4h.org/publications/curriculum, it adds a teen-targeted activity to 4-H entomology curricula offerings such as "Bugout," "More Bugout," "Metamorphosis," "Creepy Crawlies," "What's Bugging You" and beekeeping projects.

"There has been a general shortage of entomology-related 4-H curricula anywhere for this early teen age group. CSI seemed like the perfect activity," said Bambara.

"The basis of all 4-H curricula is learning by doing. I don't try to heavily teach subject matter, but rather use it to teach life skills - leadership, working with others, learning how to think and self-expression. From the entomological standpoint I also hope to reduce any fear of insects they may have.

"I would like teens to work together, examine data and use it to solve a problem," he said. "During the course of the activity, I hope they will realize the potential use of life sciences in practical applications. I hope they find it fun."

Bambara's favorite of the four scenarios is "determining how the horse turned up dead." As for his own participation in the CSI curriculum he helped create, "I find forensic entomology interesting," he said, "but personally don't have the stomach for it."