Brood XIII

Every 17 years, Brood XIII tunnels en masse to the surface of the ground, mates, lays eggs in tree twigs, and then dies off over several weeks.

[6] Some of the Northern Illinois Sub-Brood (part of Marlatt's XIII) cicadas emerge 4 years early, as they did in the Chicago area during 2020.

However, the two broods were not expected to overlap except potentially in a thin area in central and eastern Illinois (Macon, Sangamon, Livingston, and Logan counties).

[8] After the 2007 Brood XIII emergence had ended, many people in Chicago's suburbs reported in early August the development of rashes, pustules, intense itching and other skin conditions on their upper torso, head, neck and arms.

[9] The mites usually feed on oak leaf gall midge (Polystepha pilulae) larvae and other insects, but, as Zaborski found, also parasitize periodical cicada eggs when those are available.