A recent encounter with the carcass of a white-tailed deer (dead of unknown cause), has left me to ponder the world of the scavenging insects. Necrophila americana (shown above) is a good example. This particular beetle is 0.5 to 0.75 inches in size. It has a yellowish thorax with a dark center. The wings are somewhat short for a beetle, thus leaving the tip of the abdomen exposed. Goose Pond FWA is within the geographic range of
this species. As the name suggests, this insect is commonly found feeding and reproducing on the bodies of dead animals. The genus name refers to this habit as it is derived from the Greek words nekros (corpse) and philia (affection).
Saprophytic beetles such as the American carrion beetle, the American burying beetle, and dermestid beetle are able to locate dead animals at great distance by using odor receptors on their antenna. When the American carrion beetle arrives at a carcass, it begins to lay eggs. It will also work to eliminate competition from other scavenger insects (such as flies or other beetles) by eating their larvae. In a few days, larvae emerge from the eggs and begin to feed upon the host carcass. The larvae will, like the adults, eat the immature of other scavenging insects. They eventually move into the ground to pupate.
The American carrion beetle is also a fascinating example of mutualism. Mutualism is a symbiotic relationship in which the associated species benefit one another. In this case, there are small mites that hitch a ride on the beetle. Once a carcass is reached, the mites climb down from the beetle and begin feeding on the eggs and larvae of flies that have previously reached the dead host animal. Many will climb back up and catch a ride to the next carcass. Others will wait and attach to new carrion beetles emerging from the pupae. It is thought that the mites provide benefit to the carrion beetle by eating bacteria or fungi that may have gotten onto the insect while it was feeding.
Although we may find the habits of animals such as the American carrion beetle disquieting or even repulsive, they are valuable members of the ecological community. Just think of a world without scavengers or decomposers (bacteria, fungi). Without them, we would have quite a mess on our hands as the bodies of dead organisms would simply remain lying in place. How inconvenient when driving or walking to have to continuously make detours around dead Apatosaurus, giant ground sloths, and mastodons!
Pardon my facetiousness, for the role of scavenger and decomposer organisms really is critically important. The major elements needed to build the bodies of living things are carbon, hydrogen, oxygen, and nitrogen. Earth is basically a closed system. We do not receive new supplies of these (and other) elements from outside the planet. All the elements that comprise the bodies of living things were captured during the Earth’s initial formation. This means that, for new life to be possible, these elements must be continuously recycled. Otherwise they would remain locked up and unavailable in the bodies of dead organisms. Functioning as nutrient recyclers is the vital role of scavengers and decomposers.
In fact, this continual recycling of the materials that make up the bodies of animals, plants, and other organisms leads to an interesting paradox. Because of nutrient recycling, it has been postulated that the mass of all the organisms that have ever lived upon Earth exceeds the mass of the earth itself. Pretty impressive work for a group we often look down upon with disdain I’d say.
individual beetle by Michael K Oliver at commons.wikimedia.org
group of beetles at work by Phil Myers. Mus. Of Zool., Univ. of Michigan
carrion beetle larva by Linda Taylor at commons.wikimedia.org
carrion beetle with mites courtesy of beneficialbugs.org