2022/03/28 10:25 Weathernews
“Deep digging commentary” to Yukio Minamiya, Senior Researcher, Nature Division, Faculty of Arts and Sciences, Tochigi Prefectural Museum, regarding the unknown “secret” of pill bugs, such as why they curl up and what kind of food they like. requested.
Isn’t defense the only reason for curling up?
“First of all, to protect once morest natural enemies. The creatures that can be said to be natural enemies of pill bugs include frogs, salamanders, ants, centipedes and some birds. The pill bugs have a hard shell when they attack. I cover it with a frog and overdo it.
In addition to defense, there is another major reason why pill bugs curl up, “to protect themselves from dryness.”
The crustacean pill bug was originally a creature that lived in the sea like shrimp and crabs. Therefore, even if they go up to land and live, the function to prevent the evaporation of water is not fully developed, and they are very vulnerable to dryness. “(Mr. Minamiya)
99.9% are exotic species that have been introduced since the Meiji era
“99.9% of the pill bugs we can see in urban areas and around homes are exotic species, such as the pill bug, which originates from the Mediterranean coast.
It is not well known how it came to Japan, but the existence of an exotic species, the pill bug, was confirmed in the Taisho era regarding 100 years ago. It is thought that they lurked in the soil of pods containing imported plants and landed and spread throughout the country. “(Mr. Minamiya)
It is surprising that alien species have begun to inhabit all over Japan in just 100 years.
“One or two years following birth, pill bugs lay dozens of eggs twice a year. It is thought that breeding has progressed because there are relatively few natural enemies of pill bugs in urban areas of Japan. increase.
Also, because the appearance of being easily caught around the house and curling up is lovely, the children’s bringing back the pill bug for observation may have influenced the expansion of the habitat. “(Minamiya) Mr. Miss)
Where are the native species?
“The native species rarely live in urban areas, and the pill bugs live on the beach and the pill bugs live in the forest, so there are few chances to see them.
However, if you live on the beach, you may find a pill bug by digging up the seaweed on the beach or gravel beach. It doesn’t live on rocky shores, and even if it is found, it is nocturnal, so it is often curled up during the day.
The pill bug is a forest from the coast to the mountains, and can be found under fallen trees. It may be easier to find in natural forests in warm areas by the sea.
The pill bug is larger than the pill bug and is 2 cm or more. The size of the pill bug is regarding 1 cm, which is one size smaller than that of the pill bug. It has a telson shape, so you can tell it apart.
However, neither the pill bug nor the pill bug are densely inhabited, so even if they are found, they cannot be “many at once”. “(Mr. Minamiya)
What is your favorite pill bug?
“The“ staple food ”of the pill bug is the fallen leaves. I especially like the soft leaves such as soybeans, dandelions, shavings, and morus alba. I don’t like the evergreen leaves and soybeans. The pill bug also eats raw cabbage.
Since it is basically an omnivorous food, we also eat mushrooms such as shiitake mushrooms, and if we give dried shrimp or cheese in a breeding environment, they will come to us immediately.
Since pill bugs eat young leaves grown in flower beds and planters, they may be treated as pests. “(Mr. Minamiya)
What kind of existence is a pill bug in the ecosystem?
“I eat fallen leaves, but I am not a decomposer who directly decomposes organic matter such as cellulose into inorganic matter in the body.
By cutting the fallen leaves into smaller pieces, the pill bug plays a role in making it easier for fungi and bacteria to decompose the fallen leaves in the intestines and feces of the pill bug. “(Mr. Minamiya)
How many years can a pill bug live?
“The lifespan of a pill bug is 3 to 5 years. Once or twice a year, in the spring or summer, dozens of eggs are laid in a membrane-like bag of the abdomen, and the juvenile following hatching is one month. It stays there for a while. The next year or two years following leaving the mother, it grows to lay eggs.
The pill bug molts, but it takes several days at a time, not the whole body, but the front half and the back half. Which one molts first is not stable depending on the individual, so it is a good idea to identify the individual and use it as an object of observation. “(Mr. Minamiya)
Is there any other interesting ecology when observing pill bugs?
“The pill bug is a creature that is easy to observe even for kindergarten children because it is seen everywhere and moves slowly and does not attack. It can also be bred in plastic storage containers for food.
When observing, it is good to pay attention to the habit of “alternation turning reaction” as well as “it becomes round if you poke it lightly”. The pill bug has a mysterious habit of turning alternately from right to left to right to left on a T-junction.
This is seen in many creatures and is thought to be an action to escape from natural enemies, but the pill bug is particularly remarkable in the movement of bending left and right alternately.
Even if it curls up, if you wait for a while, most pill bugs should start moving once more and turn around alternately left and right. “(Mr. Minamiya)
It is said that the pill bug activates its movement when the temperature is above 15 ° C. A pill bug that hides various “secrets” while being close to you. This spring, why not take a closer look at the interesting ecology of the adorable pill bug.
Reference materials, etc.
Interview cooperation: Tochigi Prefectural Museum (2-2 Mutsumicho, Utsunomiya City)
* The theme exhibition “Roly-poly” is being held until August 21st.
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