ST. LOUIS (KMOX) - Cicadas are back to this spring... and with force.
A brood of periodical cicadas will be emerging in addition to the annual ones, and they come every 13 years.
Robbie Doerhoff with the Missouri Department of Conservation says the cicadas track time while underground in off-seasons.
"It appears that the timing is based off when trees waking up in the spring and somehow they are counting a year every Spring." said Doerhoff.
Doerhoff says they count years based on the chemicals concentration found in different tree saps
Doerhoff says while these insects are harmless, it will not a good spring to plant new trees.
"Female (cicadas) do create some slips and really fine twigs of trees to lay their eggs in," said Doerhoff. "It's not a good year to plant a new tree this Spring. I would recommend if you do plant a new tree, move it into the fall."
Doerhoff recommends it's best to let cicadas come, do their thing and go.