The familiar sounds of insects echo across the fields and grasslands as autumn approaches.
Most singing insects are nocturnal, but there are some species that sing during the day like crickets that can sometimes be heard competitively chirping in the lingering heat of summer.
This loud chirping also makes them relatively easy to find.
Many species of crickets exist, with around 50 species being identified in Japan alone.
One of the most recognizable species is this Emma field cricket.
Their Japanese name “Enma cricket” is said to be derived from “Yama,” judge of the afterlife, on account of the pattern on their head that looks like a diabolical face.
Whatever the case, they have been a familiar insect since ancient times.
Crickets chirp actively on hot days, with chirps weakening and intervals becoming more pronounced as the temperature drops.
This well-known rule of thumb has actually become the basis of formulas used to derive the temperature from chirping.
Several formulas already existed in the late 19th century, the most famous being that of an American scholar named Janice Pratt VanCleave.
Her theory starts by taking the average number of chirps a cricket makes in 15 seconds and designating it as the value N.
If N is 45, this value is input into the VanCleave formula to give 29.4 degrees Celsius.
This formula can be used to derive the temperature to an accuracy of 0.1 degrees Celsius.
However, this formula has an error factor of some 1 or 2 degrees depending on how the weaker chirps are counted.
Other formulas are more accurate for deriving temperatures of 20 degrees Celsius and lower.
Accuracy aside, why is it that this kind of formula can be deduced at all?
The activities of cold-blooded animals like the cricket change with the temperature, a phenomenon believed to be caused by a direct connection between temperature and the speed of enzyme reactions within the body.
This isn’t the only aspect of cricket ecology closely related to the temperature.
Male crickets chirp to gain themselves a mating partner.
If successful, they approach the female and attach a bag of sperm called a seminal vesicle near her tail.
Interestingly, the successful males then abstain from breeding activities for a given period and stop chirping altogether.
This period of abstinence is virtually identical for males of the same species.
Biochemical analysis has revealed that the mechanism behind this biological clock involves the time taken for a certain hormone to be fully replenished.
Such research makes it seem as if crickets were a kind of machine driven by temperature and hormone-based chemical reactions. Of course, that isn’t the whole story.
For example, we know that crickets are sensitive to humidity and display differing chirping behavior in wet and dry environments even if the temperature is the same.
While the ecology of crickets may be well understood on a molecular level, they posses as yet undiscovered sensors with which they measure the natural world.
Humans do not have such refined sensors with which to measure the natural world.
However, humankind posses the power of analysis, one that goes beyond our natural limitations.
The protection of this diverse and beautiful earth through the analysis of nature is a mission that has been entrusted to humankind.