Extension News

Coprophagy--Nature's Waste Recycling System

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Yard and Garden Column for the Week Beginning Feb. 25, 2005

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By Betsy Matos
Iowa State University Extension

Insects feed on a wide variety of different sources. In fact, if you can name it, some insect probably eats it. Insects feed on plants (phytophagous), animal (carnivorous), other insects (entomophagous), blood (heamatophagous), and dead organic material (saprophagous). Most of these feeding habits are obvious and well-known. However, one feeding habit that gets much less attention is the odd appetite for excrement (coprophagy). This 'delicate' subject is not very appealing to people, especially because they already think insects are disgusting.

Coprophagous insects - insects that feed on excrement, manure, or feces - are essential and important for our ecosystem to thrive. Recycling, whether of dead plants and animals and even excrement, is vital for the transfer of nutrients in the environment. Besides, think how unpleasant it would be if there was no recycling. We would be up to our necks in dead stuff and waste.

How do these copropahous insects contribute to the health and care of our yard and gardens? In natural ecosystems, such as Iowa wetland and prairies, or farm ecosystems several beetle and fly species are very important in recycling deer, other wildlife, and farm animals' excrement. In suburban Iowa, there are no cattle yards or hog confinement facilities but recycling is just as important and coprophagous insects contribute to yard and garden health. Coprophagous insects change the excrement of these animals (cows and racooons) into a form that can be easily used by the soil.

There are a few species of insects, such as beetles and flies, that are the primary coprophagous insect. In other parts of the world, moths and butterflies have been very important as well. These insects mostly use the excrement as a place for their offspring to develop. The immature stages of the insects (larva) feed on the microbes decomposing the excrement.

It's not easy being a coprophagous insect in town and competition can be fierce for cowpats and raccoon excrement. On the other hand, some barren areas around the world (desert) have a more intense competition for excrement. For example, Dr. May Berenbaum reports in the book Bugs in the System: Insects and Their Impact on Human Affairs that 4,000 beetles are attracted to a three-pound dung pat 30 minutes after its deposited by an elephant in a natural ecosystem in Africa.

Freshness is usually another important aspect for insects. Only fresh droppings of a specific moisture and temperature for the excrement will be useful. Those that are too old or too cold may be passed by.

Next time you walk your dog you may be amazed at the succession of insect species that may use your dog excrement for nourishment.

Contacts :
Betsy Matos, Entomology, (515) 294-1101, bmatos@iastate.edu@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu