City Creek Nature Notes – Salt Lake City

September 20, 2016

July 31st

Filed under: Butterfly, Insects, Pill bug — canopus56 @ 10:38 pm

Pill Bug Explosion

5 p.m. Midsummer is the most productive time for insects in the canyon. Many insects pursue an R reproductive strategy. They produce as many offspring as possible in bursts of mating in the hope that a small number of offspring might survive. In the canyon, an example is the butterfly explosion that occurs in April of each year. I have seen densities of upwards of 1000 butterflies per mile in the canyon during their brief two or three day explosion. Today, it is the turn of the lowly common pill bug (Armadillidium vulgare). But this bug is not an insect; it is a land dwelling crustacean. As I jog up the road, typically I am looking down at my feet. I count 3 pill bugs for each 25 steps in a 5-foot wide swath of road. Each step is about 2 feet long and jogging up to milepost 2 is about 10000 feet. Extrapolating this density to a 150 foot wide strip on either side of the road gives an estimate of 36,000 pill bugs. Pill bugs eat decomposing vegetation. This shows how even the smallest innocuous animal affects the ecology of the canyon. A few days later there are no pill bugs on the road.


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