Insects are a fact of summer: ants invade our picnics, flies buzz through the kitchen, sneaky mosquitoes evade our swatting hands.
Cheerful red ladybugs bring delight, while wasps and garden spiders get a wide berth. Three slightly unusual summer bugs boast clever talents such as glowing in the dark, posing as a leaf, and sipping flower nectar like a hummingbird. All three are gentle creatures that can be seen or heard in Evanston throughout the season.
One of summer’s most enchanting bugs is the common eastern firefly, piercing twilight with its yellow-green flash as it seeks a mate. Photinus pyralis (translating to illumination and fire) is really a flying beetle endowed with natural light known as bioluminescence, which occurs in insects, fish, corals, mushrooms and in tiny organisms called dinoflagellates that light up lagoons and bays around the world. The enzyme luciferase reacts with other chemicals to illuminate the glowable parts of bioluminescent flora and fauna, often warning predators that something is bad tasting or poisonous.
A firefly’s lower abdomen – called a lantern – lights up to signal that the mating game is on. The male flashes its lantern about every six seconds, and with each flash it follows a swooping j-shaped flight pattern that inspired the alternate name “big dipper firefly.” Females usually await those flirtatious flashes on the ground, flashing a response within two seconds if there is a love connection. Each firefly species has its own flash-and-response pattern, which continues until the male reaches the female.
Summer is wedding season, so it is fitting that male fireflies offer a “nuptial gift” called a spermatophore that the female uses to fertilize her eggs, if she deems the male worthy. She lays her bioluminescent eggs on damp soil – 100 or more in a single season. Larvae emerge a month later and can live through two winters on a diet of earthworms and snails, occasionally shedding their exoskeleton as they grow.
In late spring, firefly larvae go through metamorphosis as a pupa, similar to how caterpillars metamorphose into butterflies inside a chrysalis. Two weeks later, adult fireflies emerge. During their month-long lifespan, adult fireflies are known not to eat at all – their focus is to glow and mate.
Another nuptial-minded insect we might hear but not see this summer is the katydid, whose uncanny resemblance to a green leaf helps it blend in with seasonal foliage. During courtship, this nocturnal bug presents its mate with a spermatophylax – a gooey glob that both nourishes the female and fertilizes her eggs. The gift helps boost his chances of fathering her brood.
Also called bush crickets or long-horned grasshoppers, North American “true” katydids measure up to 2.5 inches long, live high up in trees, and survive on a diet of leaves, flowers, and slow-moving insects. They prefer to walk – using their wings to flutter rather than fly – so katydids may become prey for birds, bats, spiders, and snakes.
The katydid mating call is thought to sound like “ka-ty-did … she didn’t … she did … she didn’t” and is produced when katydids “stridulate” by rubbing their forewings together. The call – which resembles the shaking of a maraca – begins at dusk, and goes on from mid-summer well into autumn, when pre-winter frost ends the year-long katydid lifecycle. (Listen to a brief recording of katydids: http://tinyurl.com/katydidsounds).
Like many insects, a katydid’s sole purpose in life is romance and family. After being wooed and mated, the female lays her flat eggs in neatly overlapping rows on a branch or in the ground, where they remain until the following spring. Newly hatched katydids look like mini adults, shedding their exoskeleton several times until they reach adulthood and fill summer nights with their own maraca love call.
Moths commonly flutter around porch lights on summer evenings, but daytime is when the clearwing moth hovers among nectar filled flowers, looking curiously like a small hummingbird or large fuzzy bee. Appropriately named Hummingbird Clearwing moths, they make intriguing visitors to summer gardens.
With olive green heads, reddish-brown bodies and a fan tail, Hummingbird Clearwings measure 1.5 inches long with a 2.25-inch wingspan – half the size of a ruby-throated hummingbird. When they start to fly as new adults, the surface of their wings flakes off, leaving them clear with dark veins and borders like delicate stained glass windows. Those clear wings flap about 25 beats per second (hummingbirds flap at least twice as fast), generating an audible hum. They sip nectar – typically from honeysuckle, bee balm, phlox, clover and lilac flowers – through a long hollow tongue which stays coiled under their chin until needed.
Female hummingbird moths attract mates by emitting pheromones – scents given off by animals and insects that only others of the same species can detect. Males pick up the scent with their antennae, sometimes from great distances. After mating, females lay dozens of tiny green eggs on the undersides of honeysuckle, viburnum, plum, cherry, and hawthorn leaves. Adults die soon after mating.
Each clearwing egg hatches into a green horn-tailed caterpillar with tiny red spots, which feeds on the host plant. When fully grown, the caterpillar spins a cocoon around itself and rests or “pupates” during winter under the protective cover of leaf litter. Come spring, a new brood of adult hummingbird moths emerges to delight and mystify once again.