Month: June 2020

Nights in your backyard at this time of year are filled with spectacular light displays created by lightning bugs, otherwise known as fireflies.  There are over 170 different species in the U.S., and fireflies can be found in every state except Hawaii, and on every continent except Antarctica.  The flashes are a form of communication, mainly for trying to attract a mate.

Not all fireflies in the U.S. are ‘flashers’.  Some species are active only during the day and do not emit any light; several species are known as glowworms and emit a steady, glowing light.  Here in the Midwest and farther east, most species are ‘flashers’.  Flashing is a form of communication used in seeking and finding a mate.  The light is a byproduct from a bio-chemical reaction of oxygen with the enzyme luciferan plus ATP and manganese.  Different species will emit different colors of light from green to yellow to orange.  Colors can also be influenced by what time of day it is and how well they will show up against the background colors of the habitat.  Firefly enzymes have been widely studied by medical research facilities where doctors have been able to inject the enzymes into a test specimen and  duplicate the light emission to provide imaging of internal cell structures.  This procedure, known as bioluminescence imaging, is at the forefront of emerging technologies for studies of viral infection.

Fireflies are part of the beetle family and as in all species in this family, they undergo complete metamorphosis including four stages: egg, larva, pupa, and adult.  Fireflies lay eggs in late summer in rotting logs, moist soil or deep mulch.  Larvae hatch in three to four weeks, and they are voracious predators of soft bodied invertebrates including snails, slugs, spiders, and earthworms.  Larvae live from one to two years, overwintering underground or deep in rotting wood.  They molt often during this stage of eating and growing.  Larvae pupate in late spring either in an underground burrow or in some species, by attachment to a tree branch where they hang upside-down.  In two to several weeks, depending on the species, a biochemical transformation will take place changing the larva into an adult.  After adults emerge, their only function is to reproduce.  Adults generally do not eat, but may sip nectar or maple sap as a secondary source of moisture.   They live only a few weeks finding a mate and laying eggs  before they die.

Fireflies can be found in a wide variety of habitats including rivers, valleys, ponds, fields, marshes, forests, cities and urban areas.  There has been very little scientific study of firefly population characteristics, and we are just starting to accumulate this data.  Therefore, little is known as to whether they are declining, but there is anecdotal data to suggest that there were many more fireflies thirty to fifty years ago.  It is known that 3/4 of all species are active only at night.  Species in our area can be affected by habitat loss, herbicide use, and artificial night light which can obscure firefly communication and adversely affect breeding success rates.

It is fun and entertaining to be out on a quiet evening and enjoy the light displays being put on by these small insects.  You can help keep their populations strong in several ways.  Retention of leaf litter and logs, especially rotting wood, in forested or other areas will provide spaces for egg laying and larvae to live.  Consider reducing outdoor lighting at night including garage and walkway lights and buildings with all night lighting.  The use of motion detectors on timed circuits so lights are only on for a limited amount of time will greatly cut down on the amount of light present at night.  We hope you get out to see these wonderful gems, but remember if you are out looking for fireflies that flashlights, cell phones and camera flash units are all forms of artificial light that are best avoided to enhance your outdoor viewing experience.

We are hearing a lot of buzzing in our backyards right now.  The sound is coming from one of the loudest insects found anywhere in the world, cicadas.  Cicadas are members of the family Cicadidae, and are they close relatives of leafhoppers.  Sometimes misnamed as locusts, cicadas are non-jumping insects not at all related to either locusts nor grasshoppers.  There are over 150 species of cicadas in the U.S., with about 12 occurring here in northeastern Illinois.  The cicadas we see and hear are all adults; some are species that we see every year, and some are species known as “periodic species” that only appear every thirteen or seventeen years.

Species seen each year usually live underground for two to four years with some portion of the population emerging every year as adults.  Periodic species will live either 13 or 17 years underground and all of the population will emerge together in one year.  After emergence, adults go through one final molt to climb out of their old skin, pump blood into their wings and then let the wings dry and harden.

During this time, we may see hundreds of empty skins hanging from plants only to fall off and decompose.  Adults will then mate, lay eggs, and die.  Eggs are placed in holes or slots cut into tree limbs by the adult female.  They hatch after a few weeks, and the young crawl to the edge of the branch and drop off into the soil below.  They burrow their way underground and attach themselves to tree roots, where they will live until adulthood by sucking on tree sap.  A large population of individual cicadas living in a specific location is called a brood.  Twelve different broods of 17-year cicada species and three broods of 13-year cicada species have been identified throughout the eastern half of the United States.  In addition to a unique location, each brood emerges in a different year. 

Each species of cicada has its own distinct song, but all cicadas create their sound from a unique pair of organs called tymbals.  They are located on either side of the abdomen and consist of a membrane stretched across ribs.  As muscles contract, each rib buckles against the membrane with a snap.  A special air sac located in the same area amplifies the sound.  A cicada can perform this action several hundred times per second, and the resulting sound is a loud buzzing that can be heard for long distances. 

Cicadas are daytime singers and each species sings in a particular portion of each day.  In most species, only the males sing, and they start with a calling song, trying to attract a female.  When an interested female comes close, she will signal her presence with a snap of her wings.  Once the male hears her, he will change his song to a courtship tune that attracts her further and has her snapping her wings more vigorously.  This helps to guide the male to her and after locating her he will sing a third tune, a mating song.  

I encourage you to listen for the different songs sung by the male throughout the courtship proceedings as well as different songs from the three to four species currently active in this area.