Periodical Cicadas Nearing the Surface
With the more spring-like weather stimulating me to do yard work lately, I’ve done some shoveling in my yard in mid-Missouri. On three occasions, I have uncovered the nymph stage of periodical cicadas, a few inches below the soil surface. The one I found yesterday was in my garden, in soil that has been tilled annually for years. That got me to wondering about how deep in the soil those nymphs have been for the past 13 years.
The Internet references don’t all agree, but it seems that nymphs may burrow as deeply as 18 to 24 inches deep when they enter the soil. There they spend years sucking on the sap from tree roots, growing and molting their old exoskeletons. Having never tilled my garden to a depth greater than about a foot, the bugs must have escaped my digging until this year, the year of their emergence. Now they are working their way to the surface for an emergence later this month or early in May. In my reading about periodical cicadas, I came across several interesting facts:
- Although annual cicadas are found in other countries, the periodical ones (with synchronized emergence) only occur in North America, east of the Rockies.
- The annual cicadas also take multiple years to develop but their emergence is not synchronized, so we have some of them to hear every summer.
- The pilgrims of the Plymouth Colony encountered periodical cicadas and were told by the Native Americans that they preceded disease epidemics.
- The ones to emerge soon are Brood XIX, called the Great Southern Brood. On their last appearance here, they emerged along with the 17-year-cycle Brood IV in western Missouri, an event that occurs only every 209 years. Brood XIX occurs from Oklahoma to Virginia and from southeastern Iowa and northern Illinois to the Gulf Coast.
- Tree growth sometimes declines the year after emergence due to root feeding by the nymphs.
- Turkeys and other insect-eating birds get a nutritional boost by feeding on the numerous dead adult cicadas that die after mating and egg-laying occurs.
- Squirrels can suffer in the winter from a reduced nut harvest due to broken branches on mast trees from the weakened twigs where the cicadas’ eggs are laid.
I felt bad about disturbing those three cicadas that I dug up after they’d spent 13 years waiting for their big show. But after the emergence in a few weeks, I don’t think those three are going to be missed.