Spring’s abundant rainfall has resulted in lush growth in plants and excellent conditions for detritivores. Unlike predators such as lady beetles or praying mantids that occupy exalted places high in the food chain, detritivores occupy lower rungs on the ladder of life. Detritivores are Mother Nature’s clean-up crew. Their important task is to eat dead things such as fallen plants and animals and return the minerals locked-up in leaves, fruits, and stems to the nutrient cycle. We visited other recyclers in previous episodes including rhinoceros beetles, millipedes, termites, and bess beetles.
While pondering my compost pile this week, I was delighted to see herds of isopods grazing on my rotting vegetables. Isopods are a clan of arthropods rather distantly related to insects. They belong to a group of hard-shelled creatures called the crustaceans. Crustaceans include tasty, familiar delights like crabs, lobsters, and crayfish. Isopods commonly occur in marine environments where they eat algae, diatoms, and decaying vegetation. Long ago, some adventurous members of the isopod lineage moved from the sea to the land. These explorers were the ancestors of the isopods in my compost heap.
This ability to roll into a tight ball resembling a pill gives pillbugs their name.
Most gardeners know these curious creatures by the names sowbug or pillbug. The name pillbug stems from the ability of these critters to roll into a pill-shaped ball when threatened, much like an armadillo. This defensive posture makes the tender underbelly of the pillbug difficult to reach. Armor-like plates on its back shield the pillbug from attack. They are common in damp habitats beneath leaf litter, compost, boards, and stones. Wonderful moist springs and summers like the one we are enjoying this year create favorable conditions for explosions of pillbug populations. While pillbugs and sowbugs play an important role as recyclers, when too numerous, they may damage the tender roots and stems of plants in greenhouses or gardens.
Folks sometimes are dismayed when pillbugs appear in basements or garages as they move about in search of dead things. Keep mulch away from foundations, maintain door sweeps, and caulk openings to discourage unwanted visitors like pillbugs from entering your home. My compost heap is a smorgasbord of various rotting things. This week lettuce, tomatoes, and carrots were on the menu. As the pillbugs appeared from the moldering depths of the compost, they eschewed lettuce and tomato, headed straight for carrots, and devoured them with gusto. At first, this seemed strange, but perhaps the pillbugs were heeding warnings to avoid eating tomatoes due to possible contamination by salmonella and avoiding heads of lettuce contaminated with E. coli. Who knows?
References
We thank Dr. Shrewsbury for the inspiration for this Bug of the Week. To learn more about pillbugs and sowbugs, please visit the following web sites:
http://www.answers.com/topic/isopoda-1
http://insected.arizona.edu/isoinfo.htm http://insects.ummz.lsa.umich.edu/MES/notes/entonotes3.html