Quick Identification Guide for Distinguishing 17-Year Periodical Cicadas

Periodical cicadas are among the most fascinating and unique insects in North America. Known for their synchronized mass emergences every 13 or 17 years, these cicadas have intrigued scientists, naturalists, and curious observers alike. Of particular interest are the 17-year periodical cicadas, which emerge in vast numbers after spending nearly two decades underground. This article provides a comprehensive guide to quickly identify and distinguish 17-year periodical cicadas from other cicada species and similar insects.

Understanding Periodical Cicadas

Before diving into identification tips, it’s important to understand what makes periodical cicadas special:

Life Cycle: Periodical cicadas spend 17 years (or sometimes 13) underground as nymphs, feeding on tree root sap. After this long developmental phase, they emerge synchronously in large broods.

Synchronous Emergence: Their mass emergence overwhelms predators and facilitates mating in a narrow time window.
Species Groups: There are three main species groups of 17-year cicadas in the genus Magicicada: Magicicada septendecim, M. cassini, and M. septendecula.

Now that we understand their life cycle and behavior, let’s explore how to identify them quickly.

Physical Characteristics of 17-Year Periodical Cicadas

Size and Body Shape

Medium Size: Adult 17-year cicadas are generally medium-sized insects, with body lengths ranging from about 1 to 1.5 inches (25-38 mm).
Robust Build: They have stout, somewhat broad bodies compared to many other cicada species.
Wings: The wings are transparent with prominent dark veins, extending beyond the abdomen when at rest.

Coloration

Black Bodies: Unlike annual cicadas that often have greenish or brown hues, 17-year periodical cicadas predominantly have jet-black or very dark thoraxes and abdomens.
Bright Red Eyes: One of the most distinctive features is their striking bright red compound eyes. These vibrant red eyes are often the quickest visual cue for identification.
Orange Wing Veins: Their wings feature orange or reddish veins along the edges near the base, contrasting with the clear wing membranes.

Orange Markings on Abdomen: On the underside of the abdomen and sometimes on the sides, there may be orange or reddish markings.

Distinctive Features by Species Group

Magicicada septendecim: Largest of the three groups, with orange-veined wings and red eyes; also has an orange stripe down the middle of the pronotum (the plate behind the head).
Magicicada cassini: Slightly smaller, darker wing veins (less bright orange), typically no central orange stripe on pronotum; eyes bright red.

Magicicada septendecula: Rarest and smallest group; darker overall with less pronounced coloration.

Behavioral Traits to Identify 17-Year Periodical Cicadas

Synchronized Emergence Timing

One of the fastest ways to identify a cicada as a 17-year periodical species is by observing when it appears:

They emerge en masse during specific years tied to their brood schedule.

For example, Brood X is one of the largest 17-year broods and emerged most recently in 2021.
If you see massive numbers of black-bodied cicadas with red eyes all at once during a known emergence year in your region, they are almost certainly 17-year periodical cicadas.

Nocturnal Activity at Emergence

During their initial surface emergence phase (nymphs coming out of soil), they tend to surface at night or early morning before becoming active during warm daylight hours.

Loud Mating Calls

Male periodical cicadas produce loud, distinctive mating calls that differ between species groups:

M. septendecim produces a high-pitched “weeeee-whoa” sound.
M. cassini males emit a more rapid and pulsating buzzing call.

The sheer volume, often reaching over 100 decibels, and continuous chorus is characteristic of these periodic emergences.

Differentiating From Annual Cicadas and Other Insects

Annual Cicadas

Annual cicadas appear every year rather than in synchronized mass emergences. They differ in several ways:

Coloration: Annual cicadas often have greenish or brown bodies rather than black.
Eyes: They usually do not have bright red eyes; colors can range from green to brown.

Size and Shape: Annual cicadas can vary widely but tend to be less robust in build.
Emergence Pattern: Appearing in small numbers over many years rather than massive synchronized emergences.

Other Similar Insects

Birds, beetles, leafhoppers, or other bugs might be confused with cicadas at a glance, but key differences include:

Body Shape & Wings: Cicadas have large membranous wings held roof-like over their bodies.
Sound: Only male cicadas produce loud calls via specialized organs called tymbals, no other insect produces this kind of sustained chorus.
Size & Eyes: The combination of size with bright red eyes is unique among North American insects.

Where to Look for 17-Year Periodical Cicadas

Identifying these incredible insects also depends on knowing their preferred habitats:

Wooded Areas & Forest Edges: Periodical cicadas favor deciduous forests where mature trees provide ample roots for nymph feeding.
Suburban Neighborhoods with Trees: They can often be found in parks or tree-lined streets where suitable host trees exist.

Emergence Sites: Look for small holes or tunnels in soil where nymphs exit, emergence often occurs on loose soil around tree bases.

Tips for Observing Without Harm

If you encounter a mass emergence of these fascinating creatures:

Avoid Handling Excessively: Though harmless to humans, handling can injure these delicate insects.

Observe Their Calls Safely: Use ear protection if close to large choruses, they can be very loud!
Photograph Quickly and Respectfully: Try to capture photos without disturbing broods too much.
Help Spread Awareness: Share knowledge about their unique life cycle to encourage conservation-minded appreciation.

Common Misconceptions Clarified

“They Bite or Sting”

Periodical cicadas do not bite or sting humans. While females have ovipositors used for laying eggs inside tree branches, they cause no significant harm to people.

“They Appear Every Year”

Their iconic synchronized appearance happens only every 17 years for these specific broods; other years see no such mass emergence.

“They Damage Trees Severely”

While females lay eggs by slicing small slits into twigs, mature trees typically tolerate this without serious damage. Young saplings may be more vulnerable under heavy loads.

Conclusion

Distinguishing 17-year periodical cicadas can be straightforward once you know what traits to look for:

Medium-sized stout bodies with jet-black coloration
Bright red compound eyes , possibly the most distinctive feature
Orange-veined transparent wings
Mass synchronized emergences every 17 years
Loud distinctive mating calls during warm daylight hours
Habitat around deciduous forests or mature trees

By understanding these key physical and behavioral characteristics alongside knowledge about their life cycle timing, anyone can quickly identify these remarkable insects during their spectacular periodic appearances. Whether you’re a casual observer or an enthusiastic entomologist, spotting a brood of 17-year periodical cicadas is an unforgettable experience that connects us directly with one of nature’s most extraordinary biological rhythms.