EPOW - Ecology Picture of the Week

Functions of a Ground Beetle

Green Pubescent Ground Beetle (Chlaenius sericeus), Family Carabidae
Hoxworth Springs, Coconino National Forest, Arizona USA

Explanation:  You can find this beetle widely distributed from southern Canada through the United States and into northern Mexico.  You can find it listed in a wide variety of insect field guides.  You can find it on dozens of websites.  And in many scientific publications.  

But good luck finding much information on this organism's ecological functions.  That's where this EPOW episode steps in.  

This week's focus is a Green Pubescent Ground Beetle, found commonly along margins of streams, ponds, lakes, and wetlands, and in wet grass.  I discovered this specimen in a grassy wetland of Hoxworth Springs in Coconino National forest of north-central Arizona.  

But what do ground beetles -- and this particular species -- actually do in, or to, their ecosystem?

Consider their diet:  One reference (Milne et al. 1980) notes that their food consists of slugs, snails, other small insects, and other animal matter.   Another source (Evans 2008) adds that captive specimens are reluctant to attack live prey, and likely consume dead or dying insects and other small arthropod species.  Put these clues together, and one can at least hypothesize that this species plays an ecological role -- perhaps a very important one -- of recycling nutrients from insect and arthropod carcasses, returning organic compounds back into the ecosystem to support a further living food web.  

Moreover, it has been found that ground beetles can be important signals and "bioindicators" of the degree to which forest management can be sustainable (Pearce and Venier 2006).  

Sometimes it greatly pays to look more closely and think more broadly when encountering what seems to be a minor element of our ecosystems!  

    
Information:
    Evans, A. V. 2008. Field guide to insects and spiders of North America. Sterling Publishing, New York. 497 pp.
    Milne, L., M. Milne, and S. Rayfield. 1980. National Audubon Society field guide to North American insects and spiders. Alfred A. Knopf, New York. 989 pp.
    Pearce, J. L., and L. A. Venier.  2006.  The use of ground beetles (Coleoptera: Carabidae) and spiders (Araneae) as bioindicators of sustainable forest management: a review.  Ecological Indicators 6(4):780-793.