Do you know that dragonflies are nature’s own way of controlling the mosquito population? Dragonflies are considered as one of the best predators for mozzies as they can eat large number of mosquito larvae in their larval form, which takes place in the water.
In fact, an article by The Science Times stated that a study found that dragonfly larvae could play a significant role in the regulation of mosquito populations. Although they are most effective during their larval stage, adult dragonflies can roughly still eat close to 100 mosquitoes per day.
Have you recalled being bitten by a mosquito near Garden by the Bay? Well if you do not recall being bitten, you may have to thank the dragonflies for it. The Nature Society had observed twenty species of dragonflies near that area, in Marina South and 18 in Marine East.
In Singapore, a study by the National University of Singapore (NUS) revealed that there are 131 species of dragonflies recorded in the country. It comprises of nine nationally extinct and 122 extant species. Of the extant species, 14 are of highest conservation importance because they are considered critically endangered and very rare.
However, another study by NUS stated that the “true figure may have dropped”, with “alleged loss of several species, in particular, those associated with habitats such as forested to open streams with fringing bank vegetation.”
It’s no surprise that dragonflies have become a rare sight today. This is mainly due to the missing ponds which are their natural habitat, with more construction and development taking place in the country at the cause of green lands where places such as Bukit Brown, are being demolished for a highway.
A blog post by NUS said that “land reclamation has destroyed much of our native ecosystems. Our coastal works have decreased mangrove forest cover to 0.5% of Singapore’s total land area from 13% originally and we are left with approximately 35% of our original corals.”
The disappearing dragonflies may seem worrying, especially with the recent hike of dengue cases in the country. In July this year, the National Environment Agency (NEA) pointed out that the figure for dengue cases in a week has hit a new 5-year high, with 665 cases recorded between 7 to 13 July.
“A total of 7,373 dengue cases have been reported this year (as of 13 July 2019), about five times more than the 1.481 dengue cases we saw in the same period last year,” said NEA.
Minister for the Environment and Water Resources Masagos Zulkifli noted that the increase in dengue cases this year is attributed to three factors – an increase in mosquito population, the relatively warmer weather and lower herd immunity in the population.
It is largely accepted that the rise of the number of mosquitoes is in tandem with the increasing number of construction sites around the island and the National Environmental Agency has attributed the increased number of dengue cases this year to the higher population of mosquitoes.
Given that dragonflies being the natural predators for mosquitoes are no longer easily spotted in most part of Singapore, NEA will have to resort to artificial means of controlling the mosquito population, particularly when its plan to introduce sterile male mosquitoes did not really seem to work.
Other than the loss of natural habitat, NEA’s fogging exercise which is meant to kill off mosquitoes, tend to kill of predatory insects like dragonflies instead of the intended pest because of the timing of the fogging. Mosquitoes are active only during dawn or dusk but fogging happens only in the day.
In other news, the World Mosquito Program (WMP) has pioneered a method where male and female Aedes Aegypti mosquitoes are infected with the disease-resistant bacteria called Wolbachia before being released into the wild instead of trying to cull their population.
In a matter of weeks, baby mosquitoes are born carrying Wolbachia, which acts as a disease buffer for the bugs — making it harder for them to pass on not only dengue, but Zika, chikungunya and yellow fever.