How Cicadas Work

Episode Summary

Executive Summary: The episode is a humorous, information-rich Stuff You Should Know discussion about periodical cicadas, especially the 17-year brood emerging along the eastern U.S. The hosts explain their biology, loud mating calls, synchronized life cycle, predator-satiation strategy, and harmlessness to humans, while plugging a Science Channel special and briefly touching listener mail about scopolamine in Colombia.

Main Topics: Periodical cicadas and the 2013 emergence (Priority: 5/5): The hosts focus on the 17-year periodical cicadas making headlines, especially Brood II along the eastern seaboard, and explain why this emergence feels like an invasion. Cicada biology and physical traits (Priority: 5/5): They describe cicadas' insect classification, wings, eyes, mouthparts, mobility limits, and appearance, emphasizing that they are awkward, non-threatening insects. The cicada song and sound production (Priority: 5/5): A major section explains how male cicadas produce loud mating calls using timbals, why the sound is so loud, and how it affects predators and humans. Life cycle, mating, and egg-laying (Priority: 5/5): The episode outlines mating behavior, oviposition into plant stems, nymph development underground, and the long subterranean juvenile stage before brief adult life. Predator satiation and synchronized emergence (Priority: 4/5): The hosts discuss theories for the long underground period, including predator avoidance and synchronized emergence that overwhelms predators through sheer numbers. Media promotion and cross-promotion (Priority: 3/5): The transcript includes promotional segments for other iHeart content and a Science Channel special featuring the hosts and cicada expert Professor Mike Raup. Listener mail: scopolamine in Colombia (Priority: 3/5): A closing listener email corrects earlier assumptions about scopolamine use, explaining it is often used by petty thieves rather than drug traffickers and describing its effects.

Key Arguments: Periodical cicadas are synchronized insects that emerge in massive numbers every 13 or 17 years, making them a rare and striking natural event. Their overwhelming numbers help them survive through predator satiation: birds and other predators cannot consume enough of them to reduce population recovery. Male cicadas' loud calls are both mating signals and a defense mechanism that can deter predators and disrupt group hunting. Cicadas are largely harmless to humans: they do not sting or bite, and while they can stress trees, healthy trees usually recover. The long underground phase is likely an evolutionary strategy tied to survival and synchronization, though the exact mechanism remains under study. The insects’ appearance and behavior are intimidating mainly in scale, not danger; their main purpose as adults is reproduction before dying within weeks.

Data Points: Brood cycle: 13 or 17 years - Periodical cicadas emerge on fixed multi-year cycles depending on brood. Approximate number of cicada species: 200 to 2,500 - The hosts note wide variation in estimates depending on source. Sound level: 94 decibels - A cited recorded cicada chorus level, compared to a lawnmower. Hearing-loss threshold: 80 to 90 decibels - Referenced to show how loud cicada choruses can be. Rock concert volume: about 120 decibels - Used as a comparison for cicada chorus intensity. Jet engine volume: about 140 decibels - Another comparison illustrating the loudness of cicada calls. Egg count per female: up to 600 eggs - The female uses her ovipositor to deposit eggs into plant tissue. Adult lifespan: 4 to 6 weeks - The above-ground adult stage is brief before death. Ground emergence temperature: 64°F average ground temperature - Used as a cue for cicada emergence timing. Emergence formula constant: 19.65 - Part of the Weather Underground-based formula for predicting emergence date. Emergence formula divisor: 0.5136 - Part of the formula E = (19.65 - T) / 0.5136. Reported density: up to a billion per square mile - A cited estimate from Professor Mike Raup describing extreme local density. Alternative density estimate: about 1.5 million per acre - Given as a peak figure for some emergence areas. Special airing window: May 26, 2013, 8 to 11 p.m. - Science Channel special 'Cicadas and Invaders 2013' broadcast time. Hosted segment: 9 to 11 p.m. - The hosts say they are appearing during this portion of the special.

Pivotal Quotes: "There's a boatload, there could be a billion per square mile, dude." — Professor Mike Raup (quoted by hosts): Used to emphasize the extreme density of emerging cicadas. "They are really sweet little boogers." — Josh Clark: A summary judgment that cicadas are intimidating-looking but harmless. "You say cicada. I say cicada." — Hosts: A lighthearted exchange about pronunciation at the start of the segment.

Implications: Listeners come away with a clearer understanding that cicada “invasions” are spectacular but natural, temporary, and mostly harmless. The episode also encourages public curiosity, citizen science, and media engagement around the emergence.