Photography courtesy of Lowell Washburn, all rights reserved.
It’s late August. Right on schedule, this year’s crop of annual cicadas are making their above ground debut as the distinctive chorus of hopeful males is beginning to fill the sultry summer atmosphere. With volumes exceeding 100 decibels, the ear piercing trill is impossible to miss. Louder than most lawn mowers; the cicada’s song is the insect equivalent of a power saw chewing through steel. For many folks, the cicada provides an audible reminder that summer heat is on borrowed time. For others, the harsh buzzing is just one more item on the list of warm weather annoyances.
But not all opinions are quite so negative. Take the giant cicada killer wasp, for example. As far as this six-legged predator is concerned, the cicada’s noisy rattling is simply the sweetest sound on earth. The admiration is far from mutual though. For emerging cicadas, the perspective is much different. For them, the huge wasps represent a cicada’s worst nightmare.
Cicada killer wasps are fearsome predators; the annual cicada is their one and only prey. The sole domain of females, cicada hunting is conducted by relentlessly searching the upper canopies of deciduous forest and urban shade trees. Whenever a cicada is located, the wasp delivers a single powerful sting; injecting a potent shot of venom that instantly immobilizes its victim. Although the cicada may exceed the wasp’s weight by three times, the cicada killer still manages to air lift her heavy cargo to a pre-constructed home tunnel. The higher the cicada is located in a tree, the easier the flight back home. In spite of the cicada’s weight and bulk, the wasp’s ‘on board computer system’ accurately calculates the trajectory and enables the incoming insect to dead center the tunnel entrance.
I’ve read that cicada killers locate prey by homing in on the cicada’s singing. Sounds reasonable, but I think there’s more to it. Only male cicadas sing and the wasps I’ve spent time observing bring in at least as many female cicadas as they do males; visual cues must be equally important. But regardless of how they actually locate prey, there’s no disputing that cicada killers are extremely efficient at what they do. During the peak of the annual cicada emergence, the wasps’ individual hunt times are incredibly brief; often arriving with new victims every 12 to 15 minutes.
Once the immobilized cicada is spirited below ground, the creep factor quickly escalates. What began as a sunny afternoon of treetop singing has suddenly become a living nightmare of Stephen King proportions. But the worst is yet to come. What lies ahead for the comatose cicada isn’t likely to make the Mother Goose A-list any time soon and this is where you might want to quit reading this column to your four-year-old.
Upon finally reaching the inky blackness of its underground lair, the female cicada killer drops her prey onto the floor the cramped room. Once the cicada has been “checked in”, the wasp lays a single egg on her victim. Mission accomplished, the wasp seals the chamber entrance with an earthen door and leaves. Like a side of beef hanging in your local locker, the paralyzed cicada lies on its back, in the dark, and waits. In two or three days the attached egg hatches, and the wasp larvae immediately begins to devour its helpless, protein packed host. Meanwhile, the larvae’s mother is busy constructing new ‘guest chambers’ and continues filling the nursery — one stunned cicada at a time.
Not all cicadas are captured, of course. Those that evade predators will deposit their eggs into the cuts they make in tree branches. When eggs hatch, cicada nymphs drop to the ground borough into the soil where the use spear-like beaks to tap tree roots for sap. Three to five years later, maturing nymphs will suddenly tunnel back to the surface. Climbing the nearest tree, the nymph splits its plastic-like skin and the anvil headed, clear winged adult emerges. Within hours, the sound of singing cicadas will fill the humid summer air. Although the adults are at least three years old, they are called ‘annual cicadas’ because a new hatch emerges above ground each summer.
The first of this year’s cicada killer eggs are already hatching and underground wasp larvae are voraciously consuming their paralyzed hosts — one stunned cicada for developing males, but two or three for growing females; the mother already knew in advance which gender an egg would become. Once its meal is complete, the larvae will spin a cocoon of sorts and then go dormant; spending the remainder of the summer, fall, and winter in the underground room its now deceased mother originally prepared and furnished.
For the majority of their life cycle, cicadas and cicada killer wasps live in complete ignorance of the other’s existence. The next generation of adults won’t appear until the summer of 2016 when right on schedule, the lives of two seemingly unrelated species will once again converge with all the synchrony of a perfectly crafted Swiss watch.