The Behavior of Sow Bugs

This topic submitted by Alex, Andrew, Augustine, Mike, Natalie, PJ, and Tim ( ) on 10/14/04 .
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Natural Systems 1 Syllabus---Western Program---Miami University


We are interested in observing the behaviors and interactions of a sowbug community. What are their eating habits? Are their reproductive cycles mainly influenced by temperature? How do sowbugs react to light?

Background Information

Closely related to the crayfish, sowbugs are not really bugs but crustaceans. Their flat, oval bodies are about a half-inch long. They have seven pairs of legs and overlapping armored plates. Sowbugs mate throughout the year, but mostly in the spring. The female has a pouch within which it deposits its eggs. After three to seven weeks, the young hatch, as many as 25 to 200. The young stay in the pouch for another six to eight weeks before emerging. The life span of a sowbug is two to five years.
Sowbugs, for the most part, eat decaying matter, including compost, mulch, grass clippings, and manure. Because sowbugs breathe through gills, they prefer damp, protected places. They group together to reduce moisture loss. As scavengers, they are often found under pots and rotting boards and will scurry for cover when disturbed. Their predators include birds and some amphibians. Sowbugs are considered to be nocturnal, doing most of their scavenging during the nighttime.

Materials and Methods

We will use two terrariums to house our community of sowbugs. One terrarium will have soil, the other sand. The terrariums will be well stocked with sowbug living quarters, such as a log and a rock with space underneath. It is known that for sowbugs, "prime habitats are under stones or in decaying wood" (Animal Fact Sheets, X). The supply of living space will be more than adequate in order to ensure the survival of future generations of sowbugs.
The sowbugs will be well cared for. Each terrarium will be supplied with basic needs for survival. The soil may be changed and the terrarium will be regularly cleaned. Food and water will be continuously replenished. The terrariums will be enclosed and will not allow an exit for aspiring escapees. The terrariums will have controlled light conditions, for this is necessary in order to conduct a light experiment upon the sowbugs. The group of sowbugs not involved in the light test will have preset light conditions for control purposes.
Not all conditions will be equal between the terrariums. In order to better understand the behaviors of the sowbugs, different methods of testing will be used on the terrariums. The main tests that will be run will be light tests, in which different lights will be used to illuminate the sowbugs in a controlled environment. The separate experiments will be performed as follows:

Experiment 1: Because sowbugs are photophobic, we will test their reactions to various light frequencies. First we will construct or move the bugs into a light free zone, and allow them to acclimate there for 24 hours. Then we will begin a 24 hour bug watch. During this watch we will schedule different light frequencies to be tested, most likely a normal light source coupled with several different colors of the light spectrum, to be determined later. The sowbugs will be observed during this entire period, and the observations made will be used to determine if the sowbugs natural instincts for nocturnal life are based upon the light spectrum. This experiment will be undertaken with the gracious help of our fellow classmates. This is our primary experiment.

Experiment 2: We will test the food preference of sowbugs using three separate food types of equal masses. We will feed them equal amounts of Equine Senior, alfalfa, and oats and apple treats, and then record how quickly each is consumed.

Experiment 3: In order to observe their reproductive cycles in an ideal spring-like environment, we will have the class help us count our sowbugs periodically by sifting them through our sand terrarium. We will record any changes in the population.

Works Cited

1.) Animal Fact Sheets: Sowbugs & Pillbugs. (2003). Retrieved September
29, 2004 from

2.) California Biota: Sowbug. (2003). Retrieved September 29, 2004 from

3.) Calow, P. Homeostasis and Fitness (in Notes and Comments). The American Naturalist, Vol. 120, No. 3. (Sep., 1982), pp. 416-419. Stable URL:

4.) Carthy, J.D. (1965). The Behavior of Arthropods. San Francisco, CA: W.H. Freeman And Company.

5.) Featured Creatures. (1999). Retrieved September 29. 2004 from

6.) Fichter, Edson. An Ecological Study of Invertebrates of Grassland and Deciduous Shrub Savanna in Eastern Nebraska. American Midland Naturalist, Vol. 51, No. 2. (Apr., 1954), pp. 321-439. Stable URL:

7.) Himmelman, John. (1999). A Pill Bug's Life. New York, NY: Children's Press.

8.) Hubbell, S.P. Populations and Simple Food Webs as Energy Filters. I. One Species Systems. The American Naturalist, Vol. 107, No. 953. (Jan. - Feb., 1973), pp. 94-121. Stable URL:

9.) Judd, W.W. Studies of the Byron Bog in Southwestern Ontario. XIV. Observations on Sowbugs Cylisticus convexus (Degeer) and Tracheoniscus rathkei (Brandt) (Isopoda: Oniscidae) (in Reports). Ecology, Vol. 44, No. 3. (Jul., 1963), pp. 615-617. Stable URL:

10.) Lawlor, Lawrence R. Parental Investment and Offspring Fitness in the Terrestrial Isopod Armadillidium vulgare (Latr.) (Crustacea: Oniscoidea) Evolution, Vol. 30, No. 4. (Dec 1976), pp. 775-785.Stable URL:

11.) Ohio State University Extension Fact Sheet: Entomology. (2000). Retrieved September 29, 2004 from

12.) Pascoe, Elaine. (2001). Pill Bugs & Sow Bugs and other Crustaceans. Woodbridge, CT: Blackbirch Press, Inc.

13.) Porcellio Scaber Behavior. (1999). Retrieved September 29, 2004 from

14.) Schram, Frederick. (1986). Crustacea. Oxford, NY: Oxford University Press.

15.) Schultz, George. (1969). How to Know the Marine Isopod Crustaceans. Dubuque, Iowa: WM. C. Brown Company Publishers.

16.) Shough, Wren W. The Feeding of Ground Beetles. American Midland Naturalist, Vol. 24, No. 2. (Sep., 1940), pp. 336-344. Stable URL:

17.) Warburg, Michael. (1993). Evolutionary Biology of Land Isopods. New York, NY: Springer-Verlag.

18.) Wehner, Rždiger. (1972). Information Processing in the Visual Systems of Arthropods. New York, NY: Springer-Verlag.

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