Water striders appear in a variety of watery environments with the onset of spring.
Around 20 species have been identified in Japan, but most people associate water striders with this species aquarius paludum.
Their long legs are covered with tiny hairs from which they excrete oil that lets them stand and agilely move across the water’s surface.
The water strider uses its front legs as sensors to gather information from ripples in the water.
The water strider ascertains the position, distance and ability of its prey to fight back by the ripples produced by struggling insects that have fallen onto the water surface.
Not only relying on these ripple sensors, water striders have a highly developed sense of sight that is thought to provide them with large amounts of information when close to prey.
Along with collecting various information, the ripple sensors on the front legs also play a vital role in interspecies communication.
Upon closer inspection, aquarius paludum are often seen beating the water surface with their rear legs to produce ripples as if to communicate with other water striders nearby.
While males predominantly produce these ripples as an act of courtship, they often target other males in order to mark their territory and convey other such information.
Water striders and their mysterious ecology are a well-studied subject.
That doesn’t, however, mean they have given up all of their secrets.
Aquarius paludum generally has three generations per year.
Adults that have passed the winter lay eggs in spring that hatch around May as the first generation.
This generation is short lived, changing with the next generation around the beginning of the rainy season.
The second generation spends the rainy season as larvae and enter a dormant state over summer before awakening to breed in autumn.
It is midsummer and water striders have gathered in this irrigation ditch prior to entering dormancy.
The duration of this summer dormancy is significantly affected by temperature and day length.
Once the summer solstice passes the days slowly start to shorten.
This group formation and summer dormancy begins when the day is about 1 hour shorter than when the water striders hatched.
When the temperature drops below 25 degrees Celsius they awake from their dormant state and commence breeding.
The correlation between group formation and day length has also been observed in other insects like the ant cow, with extensive research into hormonal secretion being conducted.
In the case of water striders, added complexity in the form of temperature changes and summer dormancy has prevented researchers from clarifying the underlying mechanism.
Why do they use air temperature and not water temperature? And how exactly are they measuring air temperature?
We know that the second generation lay eggs in autumn that hatch and pass winter as an adult, but we still don’t fully understand where they pass winter and how they emerge from dormancy.
Mysteriously dashing back and forth across the water’s surface, waters striders utilize as yet undiscovered sensors to pass their ability to detect subtle variations in temperature and day length on to the next generation.
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.