Post by Jen B
As summer winds down, a telltale hum that signals the changing seasons begins to ramp up in the fields and forests. These trills and chirps are the mating calls of tree crickets (Oecanthinae)—a group of fascinating insects that are often heard but seldom known or seen. Their small size and mint green color helps camouflage them amidst the verdant grasses, shrubs and trees of late summer.
In order to create this chorus, males flip their broad wings up at a 90-degree angle to their bodies. Rubbing the ridges of their wings together rapidly creates chirps and long trills, which are often mistaken for frogs or cicadas. The sound frequency of these calls are unique to each species within a certain range, making it possible for females to pluck out the call of a potential mate from amidst the din. While mating, the female sips a secretion produced by a special metanotal gland, referred to as the “honey pot,” located under the wing on the male’s thorax. This fluid provides nutrients that increase the chance of successful reproduction; it is so coveted that females have been known to steal sips from other mating pairs.
Male tree crickets use interesting methods to broadcast their calls to a wider audience. The two-spotted tree cricket (Neoxabea bipunctata) will call though a small hole chewed in a leaf to amplify its song (photo, left top). The snowy tree cricket (Oecanthus fultoni) uses leaves as a baffle to increase the surface area of his wings, which increases the vibrato of his song (photo, left bottom). The staccato chirps of the snowy tree cricket are commonly heard in Lake County, Illinois. The chirping rate of this cricket increases and decreases as temperatures rise and fall. Scientists discovered that if you count the number of chirps in 15 seconds and add 40 you can calculate the air temperature in degrees Fahrenheit with surprising accuracy. For this reason, the species has another common name: the thermometer cricket.
Once the song is sung, the honey pot has been sipped and mating is complete, female tree crickets deposit eggs snugly into plant stems or tree branches. The surrounding plant protects the eggs through the long, dark winter and new crickets emerge as nymphs the following spring.
As autumn approaches, the hum of the tree crickets will grow a little louder before dulling to a whisper. Because these insects reside in a variety of habitats, they are heard in almost every Lake County Forest Preserve. Take the Hike Lake County Challenge this fall, or join us on a Walk with Docs and listen for these amazing critters while out on the trail.