Voltinism facts for kids
Voltinism is a word scientists use to describe how many times an animal, usually an insect, produces a new generation of offspring in a single year. Think of it as how many "families" or "broods" an insect has each year.
This is very important for understanding the life cycle of insects like butterflies, bees, and silkworms. The number of generations can change depending on the insect's species and the environment it lives in.
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What are the Different Types of Voltinism?
Scientists use special terms to describe the number of generations an insect has per year. Here are the most common ones:
- Univoltine: These creatures have just one generation per year.
- Bivoltine: These have two generations per year.
- Trivoltine: These have three generations per year.
- Multivoltine: These have more than two generations per year. Some insects, like fruit flies, can have many generations in a short time!
- Semivoltine: This is for creatures that take more than one year to have a single generation. Their life cycle is very long.
Examples of Voltinism in Nature
Looking at real insects helps to understand these terms better.
The Speckled Wood Butterfly
The speckled wood butterfly is a great example of how the environment affects voltinism.
- In colder places, like northern Scandinavia, this butterfly is univoltine (one generation). The adults appear in late spring, lay eggs, and then die. Their young grow, turn into a pupa, and then pause their growth for the winter. This resting state is called diapause. They emerge as butterflies the next year.
- In warmer places, like southern Scandinavia, the same butterfly is bivoltine (two generations). The first generation of butterflies in the spring produces offspring that grow up and become adults in the same summer. This summer generation then lays eggs, and it's their offspring that go into diapause for the winter.
So, there is one short-lived summer generation and one long-lived generation that survives the winter. Other univoltine butterflies include the Rocky Mountain Parnassian and the High brown fritillary.
Bees and Other Insects
- The bee species Macrotera portalis is bivoltine. It usually has two or three broods each year. During the winter, the young bees stay in a resting stage (diapause) until they can turn into adults in the spring or summer.
- The Dawson's burrowing bee is an example of a univoltine insect. The young bees from one year will stay underground until the next year. Then, they come out to find a partner and build new nests for their own offspring.
What is Partial Voltinism?
Sometimes, things are not so simple. Partial voltinism is a term for when a group of insects doesn't follow just one pattern. This can happen in a couple of ways:
- Mixed Generations: In some populations, not all insects follow the same schedule. For example, in a population of green-veined white butterflies in a northern area, most are univoltine. But if the weather is extra warm, some might skip their winter rest and produce a second generation.
- Overlapping Generations: Sometimes, the generations can overlap. For example, in some types of bees, males from an early summer generation might still be around to mate with females from the late summer generation.
Why Do Insects Have Different Life Cycles?
The number of generations an insect has each year is not random. It is a result of evolution and helps the insect survive in its environment.
Many plant-eating insects are univoltine because their food source (a specific plant) is only available for a short time each year. Their life cycle is timed perfectly to match their food.
Other insects that live in wood or eat things that are always available might spend almost the whole year growing. They have a very short time as adults.
In tropical places where it's warm all year and plants are always growing, many insects are multivoltine. They can have many generations one after another because there is always plenty of food. A good example is the fruit fly (Drosophila), which can have a new generation every couple of weeks!
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