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June 2019

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Cover Story

Sharpen Your Night Vision! - Come watch a nighttime show performed by little creatures

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A long-horn beetle (Cerambycidae) captured by a praying mantis.
A long-horn beetle (Cerambycidae) captured by a praying mantis.

Article & Photo / Hung-Ming Shih

Creatures on earth depend on the operation of the sun, follow the energ y brought by the sun and the natural operation of rising at sunrise and resting at sunset, forming a diurnal group which includes human. However, some creatures do the opposite. In order to forage, breed, escape from natural predators and protect their own safety, they prefer to live in the dark and become nocturnal. As a result, many ecological behaviors have evolved, creating a diverse nighttime ecosystem which is no less than the human nightlife, particularly in insects. From early summer to end of autumn are the best seasons for observing insects at night. Let us enter their world and experience the lively nightlife of insects. Yangmingshan National Park which is close to Taipei City is a good place for everyone to sharpen their night vision. The Yangming shan National Park Headquar ter s h o l d s e vening activities ever y summer, giving visitors a chance to visit the insects at night.

Scent is an Essential Way of Communication

Ins e ct watching i s a kind of behavior in which people interact with inse cts. When the night falls, who will come out and greet us first? Did you hear a buzzing noise near your ears? A big slap, then you wi l l f ind an ins e c t “specimen” in the palm of your hand. We haven’t even seen any nighttime insects yet and already is gifted a specimen?! Taking a closer look at the specimen in hand, it has two wings, a piercingsucking mouthpar ts , and two small antennae on its small head. This is a feature to distinguish male and female. Many nighttime insects use scent to communicate. Females would emit pheromones to attract males. Therefore, males must have an extra-large pair of antennae to detect the subtle scent. The antennae of male mosquitoes are in the shape of a feather duster. Take a look at the specimen in your hand and see if it is a male or female?

Moths a lso have thi s f e ature . Most moths are nocturnal, and communication through scent is essential to them, so different types of moth would develop different antennae shapes. The most common is feather-shaped antennae; its larger area makes it more sensitive. Thread-shaped antennae are not quite as good, so some moths would cluster together through light.

We often hear the phrase “like moths to a flame.” Why does fire attract them? This is because of another behavior of nocturnal ins e c t s – p hoto ta x i s . L i g ht represents brightness, and any insect with eyes can sense it. A little bit of light in the dark is enough to attract insects. Streetlights along the countryside road are like the stages for insects at night. They are gathered with insects coming for a nighttime carnival and is the best place to observe nocturnal insects. In addition to moths, praying mantis would also come and make its order, enjoying a dinner with vast varieties. Coleopteran such as chafer beetle, long-horn beetle, and rhinoceros beetle would also linger under the lights, hoping to find a suitable companion. Walking along the country road, you can find different types of insects under each streetlight. Occasionally, you would see long-horned grasshopper and cricket coming to the party as well. This kind of insect is equipped with an even more powerful tool to attract the opposite sex, and that is using their beautiful songs.

Due to the phototaxis habit of insects, they would gather under the streetlights along countryside roads at night.
Due to the phototaxis habit of insects, they would gather
under the streetlights along countryside roads at night.
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