Oct
26
2006

Fun with beetles

Dermestid colony: (Courtesy US FWS)
Dermestid colony: (Courtesy US FWS)

First of all, check out the Museum's dermestid cam. (Dermestid beetles are scavengers—organisms that eat the remains and wastes of other plants and animals.)

If you're at the museum, go to the Science Buzz station in the Mississippi River Gallery on Level 5 to watch a live feed from the dermestid colony. Or, even better, you can look into the colony itself from the queue for the 3D theater, down by the Triceratops on Level 3.

It's a dirty job, but someone has to do it.
Rot happens. And scavengers—like dermestid beetles and turkey vultures—eat rotting things. We associate rot with death, but it also makes life possible. How? As dead plants and animals decay—helped along by scavengers—the nutrients inside their bodies are returned to the soil. That helps new plants grow and starts the food chain over again. Without scavengers and decomposers, we’d be up to our necks in dead stuff. Think of them as the ultimate recyclers!

Bad to the bone
Adult dermestid beetles are small, black, and hairy with patches of white. The brownish-gold larvae have blunt heads and tufts of long brown hair on their rear ends. And they’re hungry—an infestation of dermestid beetles can destroy a museum’s collections. So why does the Museum keep a dermestid colony? The insects eat old, dried out, mummified stuff—leather, fur, feathers, skin, hair, wool, silk, and dried food products. They eat it all, right down to the bone. So they’re valuable for cleaning skeletons.

Many insects lay eggs and develop on dead bodies, eating them as they go. Blow flies—among the first to colonize a body—come and go fairly quickly. Dermestids, on the other hand, can be found around a body as long as there’s anything to eat—from near the time of death to years later. The kinds of insects that a scientist finds with a corpse, and the ages of the larvae and pupae, can be used to estimate when the death occurred. So insect scavengers can also help solve crimes.

Young blowfly maggots on a rat carcass: Photo courtesy Aaron Tarone
Young blowfly maggots on a rat carcass: Photo courtesy Aaron Tarone

Set up a beetle habitat of your own
It’s easy to observe the transformation of complete metamorphosis when you set up your own mealworm colony. Mealworms, the larval form of darkling beetles, are commonly sold in pet stores as food for reptiles and amphibians. These beetles are completely harmless and cannot bite or run very fast. As long as they're well fed, adult beetles won't try to escape their habitat.

Materials

  • A large plastic bin, 2–3” deep
  • A bag of oat or wheat bran
  • Two layers of burlap or cheesecloth, cut to fit inside the bin
  • Light all-purpose household oil to coat the outside edges of the bin when the beetles mature
  • Approximately 50 mealworms, available at pet stores or bait shops

What to do

  1. Lay a square of burlap in the tray.
  2. Pour 1–2” of bran into the tray.
  3. Add the mealworms.
  4. Lay a square of burlap or cheesecloth on top of the bran. (This gives the older larvae a place to pupate.)
  5. Add a fresh slice of apple, potato, or lettuce on top of the bran every week. This will provide all the moisture your mealworms need. Add fresh bran as the level goes down.

Simple experiments
Develop some simple experiments to observe behaviors and record major events in the mealworms’ life cycle:

  1. Measure individual mealworms weekly and record growth rates on a graph.
  2. Place a few “control” mealworms in the refrigerator to see if they develop at the same rate.
  3. Place mealworms in the centers of some Styrofoam meat trays. Cover half of each tray with black construction paper, and hypothesize whether the mealworms will move to the light side or the dark side of the tray.
  4. Record the number of times the mealworm molts, or sheds its exoskeleton, as it grows.
  5. Record the number of weeks until their mealworms pupate, and how long they remain in the pupae.

Your Comments, Thoughts, Questions, Ideas

Liza's picture
Liza says:

They've got guts.
You're probably familiar with turkey vultures. They're among the most visible of Minnesota's scavengers.

Although they prefer to eat fairly fresh meat, just beginning to decay, they find their meals with their incredible sense of smell. You’ll often see a group, or “kettle,” of vultures circling on currents of rising air. (Vultures often ride thermals over the bluffs outside the museum.) Look for their small heads, long tails, six-foot wingspans, “tippy” flight, and turned up “fingertips.”

Vultures eat rotting meat that would make us sick. But naked heads make it hard for bacteria and other parasites to survive on the birds. And their stomach acid and urine destroy disease organisms and help prevent their spread.

posted on Thu, 10/26/2006 - 12:45pm
Anonymous's picture
Anonymous says:

There's a camera in with the dermestids, but I can't find out what it goes too and I want to be able to tell visitors. Is it a webcam?

posted on Wed, 09/02/2009 - 5:41pm

Post new comment

The content of this field is kept private and will not be shown publicly.
  • Allowed HTML tags: <a> <h3> <h4> <em> <i> <strong> <b> <span> <ul> <ol> <li> <blockquote> <object> <embed> <param> <sub> <sup>
  • Lines and paragraphs break automatically.
  • You may embed videos from the following providers vimeo, youtube. Just add the video URL to your textarea in the place where you would like the video to appear, i.e. http://www.youtube.com/watch?v=pw0jmvdh.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Images can be added to this post.

More information about formatting options