Cicada Update

by Carl Strang

Periodical cicadas in small, scattered numbers have continued to appear in a large part of DuPage County. Steve Bailey, who conducts bird surveys for the state, also has heard them in parts of Grundy and southern Cook County. So far nearly all have been singing the cassini song type, except for one septendecim-like singer reported from Fullersburg Woods Forest Preserve by Naturalist Leslie Bertram.

There are so few that prospects for reproductive success are dim.

This is the expected fate for nearly all of these vulnerable individuals, to be eaten by birds, their wings plucked off and dropped to the ground.

I witnessed such a predation event myself at Mayslake Forest Preserve. A cicada got in maybe four songs before a robin flew straight to it. The insect got out an alarm squawk, then all was still.

In an earlier post I speculated about what was going on with these cicadas, which had been quiet the previous two years. A suggestion by WBEZ radio news director and nature enthusiast Brian O’Keefe reminded me of similar ideas expressed in the scientific literature when cicadas appear outside their brood’s normal area: perhaps these were transported from the southern brood XIX range in the root balls of nursery stock. That certainly could account for the ones in residential areas and in portions of forest preserves adjacent to private lands. I checked with the Forest Preserve District of DuPage County’s nursery staff, however, and none of our tree plantings in the past 13 years have come from so far south. Some of these cicadas are half a mile or more from the nearest preserve boundary. A little mystery therefore remains, but I have concluded that my time would be better spent in other directions.

Incidentally, while documenting these scattered emergences I was listening for green-winged cicadas (Diceroprocta vitripennis), another spring species which I believe emerged in small numbers in 2007. Their buzzings were largely covered by those of periodical cicadas, however, and the only hard evidence was a single wing, like the one in the photo above, but with green rather than red veins. Some of the literature suggests a 4-year periodicity for Diceroprocta, but I have encountered none in the places I thought I was hearing them in 2007.

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