The Great Southern Brood
Brood XIX is arguably the largest (by geographic extent) of all periodical cicada broods, with records along the east coast from Maryland to Georgia and in the Midwest from Iowa to Oklahoma. Although 13- year cicadas are generally considered to have a southern distribution, the northernmost known record of this brood is in Chebanse, IL, roughly 75 miles from Chicago’s Loop. This brood includes the species Magicicada neotredecim, Magicicada tredecim, Magicicada tredecassini, and Magicicada tredecula though only populations in the contact zone contain all four species.
In the map below, cicada symbols are verified presence records and red crosses are verified absence records in our database as of January 2024. Click on points for details. Gold symbols are from Simon (1988); smaller symbols are records with a lower degree of certainty and black crosses represent records that are considered spurious. Blue symbols are from Marlatt (1923); smaller symbols are records with a lower degree of certainty and question marks represent records that are considered spurious. Symbols are in layered in the order Database, Simon, Marlatt, and symbols in the upper layers may obscure symbols in lower layers. Some absence records in the database are not shown for clarity. Note that the dates shown do not represent dates of adult emergence; rather, they represent dates on which choruses were active. Thus, in any given area, adult emergence may have occurred a week or more earlier than the dates shown on this map. This map may not be reproduced without written permission.
Illinois presents a particular challenge for understanding periodical cicada biology, because it contains both 13 and 17 year life cycles, all 7 currently recognized species, and five separate broods, some of which include disjunct populations.
Stannard (1975) published a map of all Illinois periodical cicada broods. Standard’s map of Brood XIX includes a small northern disjunct that is instead a part of Brood III, and his delineation of the brood boundary in Adams, Brown, Hancock, and Schuyler includes areas that are also part of Brood III.
In the map below, cicada symbols are verified records in our database as of February 2021. Closed circles are records of the brood from Stannard (1975); open circles represent absences of the brood. The shaded area represents Stannard’s estimation of the brood boundary. This map may not be reproduced without written permission.
Reproductive Character Displacement
An interesting feature of Brood XIX is a striking pattern of reproductive character displacement (RCD). Where Magicicada neotredecim is in contact with another 13-year species, M. tredecim, the dominant male call pitch of M. neotredecim is approximately 1.7 kHz, while outside the contact zone, its call pitch is approximately 1.4 kHz, identical to that of its putative ancestor, M. septendecim; female pitch preferences match (Marshall and Cooley 2000).
Where M. neotredecim and M. tredecim overlap, they exhibit a pattern of reproductive character displacement in calling song pitch and female pitch preferences. Within the zone of displacement, the dominant male call pitch of M. neotredecim is 1.7 kHz, while outside the contact zone, its call pitch is ca. 1.4 kHz, identical to that of its putative ancestor, M. septendecim.
