|Magicicada septendecim female (Brood X). by C. Simon|
The life history of periodical cicadas is one of the most fascinating in the insect world. To start with, very few insects have long lives – most complete their life cycles in one year or less, so a 17-year life span is remarkable. One would expect that the variability of environmental factors such as temperature, food availability or quality, etc., would allow some individuals to mature ahead of others while others might be delayed, but the coincidence of adult emergence in the proper cycle year by billions of individuals shows that there is an astounding synchrony and consistency to their developmental pace.
The adult cicadas feed on stems and branches of plants by sucking out sap, and even at high numbers this is not particularly injurious to plants. However, there is great harm done to trees in the process of laying eggs. Females use their sharp ovipositor to insert eggs under the bark of branches, causing a die-back of the branch beyond the point of injury. This damage can be very widespread and destructive to trees in forests, landscapes and orchards. In a few weeks, tiny immature cicadas called nymphs hatch from the eggs and immediately move to the ground and burrow into the soil. The nymphs, depending on the species, will spend the next 13 or 17 years below ground feeding on sap from the roots of woody plants.”
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