The “Locusts” (13-Year Periodical Cicadas) Are A-Coming!

 Lacy L. Hyche

It happens in Alabama once every 13 years. It last happened in 1985. It will next happen in 1998. The happening is the spectacular appearance, after a 13-year absence, of adults of periodical cicada Brood XIX, Alabama's primary brood of 13-year "locusts."

Photo 1. Typical periodical cicada adult of Brood XIX.

The event is remarkable and memorable. Scattered areas of deciduous woodlands suddenly become infested with millions of large, red-eyed, noisy insects (Photo 1). Trunks of trees and stems and leaves of undergrowth plants bear numerous empty brown locust skins (Photo 2), and the woods ring throughout the daylight hours with the loud, droning song of male cicadas calling to females. From past records and results of AAES studies, this historic entomological event is expected to begin sometime during the last 10 days of April and the first week of May.

Periodical cicadas (Magicicada spp.) are native to the hardwood forests of the eastern United States. Colonists in New England discovered them more than 350 years ago. These early settlers knew nothing of cicadas. They did know, however, of the stories of "hordes of locusts" of the Old World, and thus apparently applied the same name to this "horde" of unknown insects in the New World. In entomological language, the term "locusts" properly refers only to grasshoppers. Nevertheless, the name has persisted and is still commonly applied to cicadas today.

Photo 2. Cast skin of last-stage cicada nymph.

There are two groups of periodicals, 17-year and 13-year. The 17-year cicadas are mostly northern, and the 13-year primarily southern. Several individual broods occur in each group, and each brood is identified by number. Habits and manner of development are much the same for all broods, varying primarily only in length of life cycle (13 vs. 17 years) and year in which adults emerge.

The periodical cicadas of Alabama are of the 13-year group. Populations of two broods, XIX and XXIII, have been recorded as present in the state. The primary range of Brood XXIII lies west of Alabama but extends into areas of eastern Mississippi and western Tennessee bordering Alabama. In years past, a population believed to be of this brood was reported in Tuscaloosa County. Therefore, it is possible that this and other small, isolated populations of Brood XXIII may exist in northwestern areas of the state.

Brood XIX, however, is Alabama's main, and perhaps today its only, brood of periodical cicadas. The brood is well established, and populations are widely distributed over much of the northern three-fourths of the state. Three species occur in Brood XIX and, to the casual observer, all look much alike. The head is black and broad; the eyes are red. The body is black and tapers rearward; legs are red; and wings are transparent with reddish-orange veins (photos 1 and 3). Adults are 1 1/4 to 1 3/4 inches long.

Photo 3. Ovipositing female cicada. Note damage to wood of the stem at oviposition sites behind the female.

A well-established population of Brood XIX exists along the Chattahoochee River in the vicinity of Goat Rock Dam in eastern Lee County. Emergence of adults of this population on schedule in spring of 1985 provided the opportunity to observe and record habits, activity, and development of these cicadas. Findings are as follows.

The population at Goat Rock was first detected and examined on May 9. Activity had already begun. Nymphs (the growing stage) had emerged from the soil (after 13 years), molted, and left the typical cast skins (Photo 2) attached to tree trunks and understory plants, and adults were abundant on twigs, stems, and leaves. According to local residents, emergence and singing began about 10 days earlier, April 29 to May 1. The song of males (only males possess sound-producing structures) was loud and constant, but no mating or egg-laying (oviposition) was observed. Mating was observed the next day, May 10, and oviposition was in full swing by May 13.

Photo 4. Rows of cicada eggs inside hardwood twig.

The female possesses a strong blade-like ovipositor (egg-laying organ). With this she slits the bark and wood of small twigs and stems (Photo 3) and deposits a double row of eggs (Photo 4) within. The number of eggs per oviposition site varies, but is usually about 24 to 28. The act of ovipositing often severely injures twigs and stems and causes them to die (Photo 5). Cicada adults possess sucking-type beaks, but feed little, if at all; consequently, it is the egg-laying process, not feeding, that causes damage.

Ovipositing and singing continued through May 16, but was much reduced by May 20. By June 3 all adult activity had ceased. Eggs began to hatch in late June, about 6 1/2 weeks after start of oviposition. Newly hatched nymphs dropped and entered the soil to begin the 13-year period of quiet development.

Photo 5. Dead leader of young hardwood; the result of damage caused by oviposition. Note the oviposition slits along the stem.

The order of activities in the Goat Rock population in 1985 represents the typical cycle of Brood XIX periodicals in Alabama. Date of start of adult activity may vary some from year to year and by location within the state, but should fall within the period late April to early May. Adults live, sing, mate, and lay eggs for three to four weeks, then die. Following the 1998 emergence, Brood XIX will not be seen or heard again until spring of 2011. Adults of Brood XXIII in adjacent Mississippi are scheduled to emerge in 2002.