Quck answer
Periodical cicadas, also known as 17-year cicadas, have synchronized life cycles. They spend most of their lives underground, feeding on tree roots, and emerge as adults every 17 years to mate and lay eggs. However, some cicadas, known as stragglers, emerge in different years, either four years early or four years late. Scientists believe that this may be due to a combination of factors, including environmental cues, genetics, and a lack of predators in certain areas. While stragglers are not as numerous as the main brood, they can still mate and produce offspring, which can lead to more frequent cicada emergences in certain areas.
Wild Animals
Party Time for Cicadas?
While most cicadas emerge on a strict schedule, there are some known as stragglers that appear a year earlier or later than their brood. The most common time-frame for these stragglers is one year, but there are exceptions. In some cases, cicadas may appear up to four years earlier than their brood’s schedule due to unseasonably warm weather. On the other hand, delayed development may cause some cicadas to emerge late [source: Hayes].
Scientists are still unsure about how cicadas are able to keep track of time and know when 17 or 13 years have passed. One theory suggests that the fluid they consume from tree roots, known as xylem, may play a role in reflecting the yearly cycle of the tree. If the xylem signal is weaker for insects under certain types of trees, this may lead to off-schedule appearances [source: Hayes]. Interestingly, the prime number appearances of cicadas may help with survival, as their predators do not become too dependent on them for food [source: Hayes]. However, stragglers who miss the big cicada party are more likely to be eaten due to their smaller numbers.
While scientists do not fully understand why stragglers exist, they do know that their presence makes it difficult to create accurate emergence maps. Historical records of stragglers are scarce, as they can range from just a few dozen to a single cicada. Thus, it is difficult to pinpoint geographic patterns of stragglers [source: University of Michigan Museum of Zoology, Magicicada, Cicada Mania].
FAQ
1. What are 17-year cicadas?
17-year cicadas are a type of periodical cicadas that emerge from the ground every 17 years. They are known for their loud and distinct mating calls, which can reach up to 90 decibels.
2. Why do 17-year cicadas come out so rarely?
17-year cicadas have a long life cycle that includes spending most of their lives underground as nymphs. They only emerge as adults once every 17 years to mate and lay eggs. This long life cycle is thought to be an adaptation to avoid predators and synchronize their life cycles with other cicadas in their brood.
3. Why do some 17-year cicadas emerge more often than every 17 years?
Some 17-year cicadas, known as stragglers, may emerge a year or two early or late. This is thought to be due to variations in the temperature and moisture levels of the soil. If the soil is warmer and moister than usual, some cicadas may emerge early. If it is cooler and drier, they may emerge later.
4. Can 17-year cicadas emerge earlier than 17 years?
No, 17-year cicadas cannot emerge earlier than 17 years. This is because their life cycle is determined by a genetic timer that is set to 17 years. However, as mentioned earlier, some cicadas may emerge a year or two early or late due to environmental factors.
5. Why are 17-year cicadas important to the ecosystem?
17-year cicadas play an important role in the ecosystem by providing a food source for predators such as birds and mammals. Their emergence also helps to aerate and fertilize the soil, which can benefit plant growth. Additionally, their loud mating calls can attract female cicadas from miles away, which helps to ensure genetic diversity within their brood.
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