First Flags Over Brookfield

by Carl Strang

Cicada specialist John Cooley taught me a new term: flagging. This refers to dead and broken twig ends on trees and shrubs where periodical cicadas have placed their eggs. Mama cicada slits the underside of the twig in several places and injects her eggs. This impedes water flow, and with circulation cut off the leaves turn brown. The cuts weaken the twig, and it may break partly and bend down, producing a “flag.”

Now that the periodical cicadas are done singing in many places and nearly so in others, it is time to start looking for these flags. They will provide the best measure of how this off-year emergence may continue for another generation. On Tuesday I started in Brookfield, the first place where I heard a full wave chorus of singing males.

I soon found a tree with many flags.

This tree was in the same place where I found that initial wave chorus.

The brown, drooping flags stand out against the green foliage. This prunes the tree a bit but will not cause significant harm. I saw many trees with one or two flags, but only the two in the photos had many. I expect to see more of them the next time I check.

John said that dry weather and thunderstorms enhance flag formation. A lack of water flow enhances the twig-end drying, and the buffeting winds of storms partially snap the weakened twigs. I heard no singing cicadas in Brookfield, and so this is the very beginning of this process. On the way home I swung through northern Hinsdale, another area that had abundant wave chorusing at the peak. There still were many small non-wave choruses, so it was not surprising that I saw only a couple flags during the drive-through. I am hopeful that flagging will develop over a period of weeks, allowing me the time needed to get a good assessment of periodical cicada reproductive success across the Chicago area this year.

1 Comment

  1. July 1, 2020 at 6:37 am

    Interesting thanks


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: