Pillbug Fact File
Credit: Walter Siegmund, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
Wild 2-5 years
Captive 2-5 years
The pillbug is a small crustacean which has taken to living exclusively on the land. As such they must take shelter under rocks or logs during the day to ensure they do not dry out.
These animals are considered detritivores and help to break down organic matter and return it to the soil.
Females can retain sperm for up to a year after mating. This is used to fertilize her eggs and the young then develop in a pouch known as the marsupium.
They are able to defend themselves against predators due to their hard outer coating and a foul-tasting liquid they produce if attacked.
Read on to learn more about these incredible invertebrates.
What does the pillbug look like?
The body of the pillbug is an oval shape which is twice as long as it is wide. They may be colored grey or brown. Blue individuals are present in some populations. This coloration comes from them being infected with a virus. This also affects their sensitivity to light and can decrease their lifespan.
Their name pillbug is taken from their tendency to roll in to a ball if threatened.
At the front of the head are two short antennae. These are used to sense their environment.
An average adult pillbug will measure 1cm (0.4in) long. Males and females are similar in size.
What does the pillbug eat?
Pillbugs are detritivores. They feed on decaying leaves and other rotting organic matter. When food is scare they have also been observed to feed on garden roots. In backyards they may feed on the organic matter from potting mix.
On occasion adults have been seen to feed on their young.
After they shed their exoskeleton they will eat the old one to provide the calcium required for their next shed.
Credit: Public Domain
Where can you find the pillbug?
Europe is the native home of the pillbug. Here they were originally restricted to the edges of the Mediterranean sea.
Humans have enabled the spread of this species globally and they are now known from almost all landmasses except for Antarctica. They are also recorded on a number of islands such as Madagascar.
What kind of environment does the pillbug live in?
Pillbugs thrive in areas with a temperate climate. They require high levels of humidity to prevent their skin from drying out.
They will often be found seeking shelter under rocks and logs. With humans entering their habitat they will make use of discarded waste such as cardboard. They will also burrow in to the soil.
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How does the pillbug produce its young?
Mating tends to take place during spring. Males and females will both mate with multiple partners. The female can store sperm from multiple partners. It may remain in storage for up to a year before she gives birth to the young.
Females retain their eggs in a pouch on the underside of the body. This pouch is known as the marsupium or brood pouch.
Eggs hatch after three to four weeks in the marsupium. Once the eggs hatch the young are fully formed and can strike out on their own. Some remain in the marsupium for up to two weeks before doing this though. Each clutch will include between 100 and 200 eggs
At hatching the young have one fewer pairs of legs than they will as adults. This additional pair will develop at their second molt two weeks after birth.
Young molt their exoskeleton for the first time within the first day of being born. They will continue to molt every couple of weeks until 18 weeks old.
Between one and three broods are produced each year.
Sexual maturity is reached by one year old.
What does the pillbug do with its day?
These animals are one of the few crustaceans which can live permanently on land. Despite this they still have gills and as such they must remain damp to breathe.
Pillbugs are active by night but can be seen during the day under logs and debris.
The pillbug does not urinate. Instead they secrete excess ammonia from their body by passing it through their exoskeleton.
Credit: Public Domain
Predators and Threats
What is impacting the survival of the pillbug?
Natural predators of the pillbug may include invertebrates such as ants and spiders along with birds such as starlings.
Their coloration provides some level of camouflage against predation. They have a hard outer shell to provide protection if captured. Pillbugs can also secrete distasteful substances to prevent attack.
In some areas where they occur this species may be viewed as a pest of crops. Large aggregations of this species can cause damage to crops.
They may also be known as the armadillo bug due to their shared ability to roll in to a ball. Alternatively they are known as the roly-poly. In some regions they are known as the woodlouse though this name is also used for the sow bug so may cause confusion.
Credit: Franco Folini, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons
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