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Cicada locust11/22/2023 What should I do to prepare my plants for the swarm? To survive, cicadas need to show up in such massive numbers that their many, many predators just can't eat them all. So the only serious evolutionary defense cicadas have against extinction is their sheer numbers. If something wants to eat a cicada, chances are, it will. And despite having wings, they don't fly especially well. Making matters worse for individual insects is the fact that they have virtually no way of fending these predators off. Many predators will completely change their behaviors during cicada years just to feed on them. Birds, reptiles, fish, spiders, wasps and even household pets all see cicadas as protein-packed snacks. Once a cicada emerges above ground, it faces no shortage of predators. Michael Williamson/The The Washington Post via Getty Images Cicada shells lay at the base of a tree in Chevy Chase, Maryland, in 2004, the last year Brood X was seen. Such a hybridization would reduce the size of these generations - bad news for a species that needs large numbers to survive. Another theory says the prime-numbered cycle reduce the likelihood that 17-year cicadas will mate and hybridize with cicadas of different species or generations. One idea suggests that the unusual, prime-numbered lifecycle prevents generations of cicadas from run-ins with the lifecycles of wasps that prey on them. The exact reason behind the number 17 is unknown, but scientists have a few theories. The less often cicadas emerge from the earth, the lower their odds of being wiped out by an unusually cold summer. A brood can't survive a cold summer above ground, but surviving a cold summer below ground is no problem. So cicadas evolved different cycle lengths to improve their odds of survival. That's a problem for cicadas: If the temperature lingers too long below 68 degrees, it gets too cold for them to mate and survive. Back then, summers could be unpredictably cold in the eastern United States. So why do cicadas only show up in 17-year cycles?Īs it turns out, those long cycles are part of the cicada's evolutionary strategy that dates back 1.8 million years, to the Pleistocene Epoch. Most insects, love them or loathe them, make annual appearances in our homes and gardens. Brood X is endemic to much of Indiana, Pennsylvania, Maryland, New Jersey, Delaware and Eastern Tennessee. You can see the areas with the most frequent sightings in the map below. Through history, it has appeared as far west as Missouri, as far south as Georgia, as far north as Michigan and as far east as Long Island, New York. The coming Brood X (that's Brood 10 in Roman numerals) is the most widespread and prolific of the known generations. (One of these "missing" broods, Brood XI, was last seen in Connecticut in 1954.) For example, Brood IX, the brood that emerged in 2020, was localized to parts of Virginia, West Virginia and North Carolina.Ī few of these broods have never been formally observed, suggesting that they may have gone extinct long ago. Theoretically, there should be 17 different generations of 17-year cicada, each linked to a different geographic zone and a different emergence year.
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