Early stragglers of periodical cicadas (Hemiptera: Cicadidae) found in Louisiana

A historic event occurred during the summer of 2024 with broods of both thirteen- (Brood XIX) and seventeen-year (Brood XIII) periodical cicadas (Magicicada spp.; Hemiptera: Cicadidae) emerging simultaneously (Wells et al. 2024). However, Louisianians were informed that they would not experience this event as Brood XIII is limited to forested areas of the northern Midwest and Brood XIX was not known to occur in Louisiana (Marlatt 1907; Simon 1988). Brood XIX, the Great Southern Brood, is the largest of the thirteen-year broods, occurring throughout the central Midwest and much of southeastern United States. Historical records exist from the northern Louisiana parishes of Bossier, Caddo, Claiborne, Morehouse, and Washington (Marlatt 1907); however, the historical records have been reanalyzed following the misinterpretation of straggler emergences as different broods (Marshall 2001). Recent reports from the United States Department of Agriculture Forest Service indicated records in Caddo, Claiborne, and Morehouse parishes (Liebhold et al. 2013). The University of Connecticut (UConn) shows an absence of verified record data for Brood XIX in Louisiana, neither confirming nor negating their presence (UCONN 2024a). However, there were no sightings recorded in Louisiana during the last emergence event of Brood XIX in 2011 (Peveto 2024), when modern online tools and citizen scientist social media outlets were widely available.

Citizen scientists and professional entomologists, however, recorded observations and collected specimens of periodical cicadas in Louisiana during the 2024 emergence. The following natural history note documents periodical cicadas observed in Louisiana, primarily central Louisiana, and suggests that those insects observed and collected were likely early stragglers of Broods XXII and XXIII given their distribution, and not members of Brood XIX.

Documenting periodical cicada brood records is complicated in areas where multiple broods occur because small numbers of off-cycle emergences of single or small numbers of cicadas, referred to as stragglers, may occur during almost any year. Straggler emergences are plastic but are commonly associated with accelerations of 1–4 years (Cooley et al. 2018; Marshall 2001; Marshall et al. 2017; UCONN 2024b). These isolated emergences do not survive predation to mate and reproduce, so do not represent a full emergence of a brood. Thus, the number of spring 2024 iNaturalist (iNaturalist 2024) observations of thirteen-year cicadas from East Baton Rouge, Livingston, and West Feliciana parishes without indications of chorusing were likely three-year-early stragglers of Brood XXII, as Brood XXIII has not been recorded in the mentioned parishes.

Prior to the historic dual emergence of Brood XIX and XIII, state media outlets were used to advertise the expected Brood XIX emergence event in advance. This included, but was not limited to, extension articles by the Louisiana State University (LSU) AgCenter (Ashbrook and Carlton 2024; Peveto 2024) and media interviews with LSU AgCenter scientists. Citizens were encouraged to document observations using the application iNaturalist, including images, locations, and dates. Field observations during the emergence included observing adult specimens and collecting exuviae and vouchers. Male cicada calls were recognized by comparison to the calls on the UConn cicada website (UConn 2024c). Specimens were identified based on resources on the same website (UConn 2024c) and comparisons to specimens in the Louisiana State Arthropod Museum at LSU in Baton Rouge, Louisiana. All specimens proved to be Magicicada tredecim Walsh and Riley. Voucher specimens were deposited in the Louisiana State Arthropod Museum.

Eyewitness accounts of observed emergences throughout Louisiana were uploaded to the iNaturalist application by the authors and citizen scientists (Table 1). Cicada chorusing was heard and noted, and specimens were observed and collected in LaSalle parish, near White Sulphur Springs (31.574 °N, 92.279 °W). Many cicadas were unreachable in the tree canopy. Calls also were noted in the Catahoula National Wildlife Refuge, near Cowpen Bayou, in LaSalle parish (31.534 °N, 92.030 °W) and outside Winnfield in Winn parish (31.961 °N, 92.637 °W). However, because the land outside Winnfield was privately owned, the researchers were unable to obtain specimens. A map of the identified cicadas and the known ranges of different broods present in Louisiana can be found in Figure 1.

Figure 1:

Periodical cicada broods found in Louisiana parishes. Circles are suspected four-year-early stragglers of Brood XXIII and triangles represent three-year-early stragglers of Brood XXII. The data are from Marlatt (1907), Simon (1988), Koenig et al. (2011), and Liebhold et al. (2013).

Although both professional and citizen scientists have documented the existence M. tredecim in different Louisiana parishes during the emergence year of Brood XIX, there is not enough data to suggest that Brood XIX is present in Louisiana. Based upon the distribution of the broods, it is highly likely that the cicadas found in central Louisiana are four-year-early stragglers of Brood XXIII, which is expected to emerge in 2028.

The cicada habitats were similar in tree stand composition. The sites observed in the LaSalle, Rapides, Grant, and Winn parishes comprised extensive stands of loblolly pine (Pinus taeda L.; Pinaceae) and young sweetgum (Liquidambar styraciflua L.; Altingiaceae). In the case of Catahoula National Wildlife Refuge (Rapides parish), the emergences were in bottomland hardwood forest. Species for this ecosystem include sweetgum, water oak (Quercus nigra L.; Fagaceae), hackberry (Celtis laevigata Willdenow; Cannabaceae), and green ash (Fraxinus pennsylvanica Marshall; Oleaceae) (LDWF 2010), like the tree species composition observed by Sahli and Ware (2000) in Virginia.

A few central Louisiana emergence sites had been clearcut within the past 5 years and were overgrown with young sweetgums (3–8 years old) that had begun to reclaim the landscape. On those sites, M. tredecim adults were commonly found resting and calling on those younger sweetgums.

Unfortunately, continued land-use changes in central Louisiana may cause population declines of the broods present. Because M. tredecim live underground feeding on root tissue for 13 years, destruction of their habitat at any point during this extended period may cause undue stress and could eliminate the population. Hardwood tree species are especially important for Magicicada spp. for ovipositional sites (Coyle 2023). Adults have not been documented to lay eggs on loblolly pine, although it has been suspected that pine roots may support nymphal development (White et al. 1982; Sahli and Ware 2000). Land conversion to field crop agriculture and urbanization are direct threats to periodical cicadas, with impacts of cyclical forest product harvest and regeneration less clear. Clearing of woodlands and resulting decline in number of localities inhabited by periodical cicadas has been noted since the early 20th century (Marlatt 1907).

With the emergence of possible four-year-early stragglers from Brood XXIII in central Louisiana, we believe it is imperative to continue monitoring parishes across the state for periodical cicada emergences. Long-term research on periodical cicadas, including location, environment, tree species distribution, is paramount for their continued survival and documenting any potential of a shadow brood (straggler populations that are not self-maintaining) (Marshall 2001; Cooley et al. 2011). Revisiting sites during the next scheduled emergence events in 2027 (Brood XXII) and 2028 (XXIII) can help confirm the presence and range of these broods in Louisiana. This is ample time to prepare both professional researchers and citizen scientists for this event.