Hook-tailed Emperor Dragonfly becomes Taiwan, China's 160th dragonfly species, a good sign for farmland ecology

In early 2018, the dragonfly list of Taiwan, China welcomed a "new addition": after years of field surveys and comparisons by scholars and dragonfly enthusiasts, the number of dragonfly species recorded on the island increased to the 160th species, and this new member is the Hook-tailed Emperor Dragonfly. For ordinary people, knowing one more dragonfly species may not seem like much, but for those engaged in agriculture, this is actually a good sign - the more dragonflies there are, the healthier the ecology in the fields tends to be.

Many dragonflies are the farmland's "free helpers"

Dragonflies are typical predatory insects, and they feed from the water to the sky: the larvae (commonly known as water nymphs) live in ponds and ditches and can prey on mosquito larvae and other small aquatic insects; after emerging as adults, they become "hunters" in the air, and mosquitoes, flies, planthoppers, small moths and other flying pests are all on their menu. A single dragonfly can eliminate a considerable number of flying insects in a day, and in a large rice field filled with flying dragonflies, pest pressure can often be much lighter. In other words, dragonflies are "natural enemy insects" that do not need to be hired, and against flying pests they can genuinely share part of the pressure for farmers.

Dragonflies are also a "barometer" of water quality

Many people do not know that dragonflies are quite sensitive to water quality. Their larvae must live in water for several months or even longer, and once the water body is polluted, the larvae are very hard-pressed to survive. So wherever a pond or irrigation canal can reliably show dragonflies skimming the water or larvae molting, it can basically be judged that the water quality there is still acceptable. Conversely, fewer and fewer dragonflies around farmland often indicates eutrophication of the water body or excessive pesticide input, which is worth watching out for. The fact that the Hook-tailed Emperor Dragonfly was discovered this time also shows to some extent that the local area still retains a good wetland environment.

Growers can "keep" dragonflies in this way

If you want dragonflies to help, you first have to give them a place to settle. First, try to preserve the natural banks of ponds and drainage ditches at the field edges, and do not harden them all; leave some emergent plants and shrubs and grasses along the banks so dragonflies can lay eggs and emerge. Second, use pesticides with restraint, give priority to physical and biological methods such as sex pheromone lures and insect-killing lamps, avoid surrounding water bodies and the peak activity period of dragonflies when spraying is necessary, and do not arbitrarily increase the dosage. Third, do not catch water nymphs or net adult dragonflies to give to children as toys or for other uses. Fourth, if you photograph a dragonfly you do not recognize, you can report the photo to the local forestry or plant protection department or a nature observation platform; perhaps the next new record will come from the edge of your own field.

The 160 dragonfly species record is not just a number, but also the ecological foundation of a piece of land. For growers, treating these small "hunters" around them well is saving pesticide money and building up soil fertility for their own fields - why not do it?