WE tend to have mixed feelings in our views of insects, which account for 75 per cent of all animal species on earth. Certainly, there are human threatening species, among which and in particular, spiders, scorpions, and centipedes provide life threatening dangers. Our own survival and our own economies depend upon some insect species and nowhere more important than in their ecological significance in the Bornean rainforest ecosystem as decomposers, pollinators, defoliators, recyclers of dead plants and animals, and animal dung.
Some species manufacture honey and others act as biological control agents protecting our crops from other insect pests. The latter I have witnessed on a large commercial scale in the vast greenhouse flower-growing complexes along the Kenyan lake of Navasha. There, roses are grown hydroponically and instead of using pesticides to eradicate aphid populations, the farmers use especially cultivated spiders. This is a model of green farming. Sadly, in conservational terms, insects hardly pull on our heartstrings as does an orphaned orang-utan or lone polar bear on a melting ice floe.
Dengue fever and mosquitoes
In Malaysia, as in other tropical countries, the word dengue fever sets alarm bells ringing. We know that the Aedes aegypti species of mosquito are the vectors of this viral infection. By the beginning of December 2019, nearly 119,200 instances of infection were recorded that year in Malaysia and 162 deaths resulted. Research has discovered that the virus tends to be concentrated in dengue hotspots.
Trials to combat this disease have been recently carried out in eight locations in Malaysia to include Kuala Lumpur, Penang, and Selangor, by an international team of scientists from the universities of Melbourne and Glasgow combining with the Institute for Medical Research in Malaysia involving a strain of bacteria called Wolbachia pipientis. This bacterium has the ability to inhibit dengue-carrying mosquitoes from transmitting the virus to humans.
Male mosquitoes are injected with this bacterium in laboratories and then released to infect wild female mosquito populations. Their resultant offspring also bear Wolbachia and thus cannot transmit dengue fever. Already this method of insect to insect control has resulted in a 40 per cent drop of the incidence of dengue fever in humans. The researchers are confident that this is a cost effective and sustainable way to overcome the disease without the use of harmful insecticide fogging.
Locusts and famine
In the early months of 2020, Ethiopia, Somalia, Kenya, Tanzania, and Uganda were invaded by vast swarms of locusts, which have devoured food crops and cattle grazing land. These locusts spread from the war-torn Yemen in November 2019 and now number hundreds of billions. Breeding so very fast, there numbers are forecast to increase by 500 per cent by June this year! Such locust plagues Kenya has not witnessed for the last 70 years and Somalia and Ethiopia for the last 25 years. Aerial spraying of insecticides on crops and ranching land seems the only quick fix to this dreadful situation. Ugandan coffee plantations are particularly affected and as such a major source of foreign currency and revenue is severely threatened. The United Nation’s Food and Agriculture Organisation (FAO) has called upon the international community to provide an estimated RM307.4 million to fund the spraying of the affected areas thereby alleviating a famine.
Worldwide insect decline
Little is really known about the total numbers of insect species our planet holds and it is estimated that only between 10 and 20 per cent of insect and invertebrate species have been classified and named. We may well ask ourselves as to why the world’s insect population is declining with some species facing extinction? Alas, there is no simple answer but it is likely that a combination of factors are involved. Habitat loss through urban encroachment on the countryside plus agricultural developments, pollution, climate change, and invasive species that show no respect for manmade borders together with the ever-increasing use of pesticides, insecticides, and herbicides have all contributed to the loss of insect life.
Whilst pesticides may be the only way of controlling agricultural pests they often harm non-target species many of which are beneficial to farmers. Pesticides find their way into rivers thus killing many species of beetle and dragonfly, leading to a decline in river fish populations. As insect populations fall, so bird numbers also fall.
Invasive Brazilian bees have contributed to the fall in populations of European and North American species of bee and this has seen a decline in commercial honey production. These bees not only invade native bee nests to eat their larvae but also attack other bees whilst flying by biting off native bees heads!
How to stem the trend
Twenty-five years ago 950,000 species of insect had been described. Currently, it is estimated that there are between, approximately 3.6 and 10 million species of insect but the rate at which insect habitats have been destroyed since the Industrial Revolution suggests that many insect species have become extinct without us even knowing that they ever existed!
On Feb 10 this year, researchers at the University of Helsinki issued a paper warning humanity about worldwide insect decline and offered sound practical solutions “to mitigate an insect apocalypse”. Such measures included the infrequent mowing of lawns and meadows, thus allowing the grass and other plants to grow and insect life to proliferate. Other suggestions included planting native trees, avoiding pesticides, leaving old trees, stumps, and dead leaves all of which attract various forms of insect life. Perhaps we all like to tidy our gardens too frequently.
Insects on Borneo Island
Exactly a decade ago, a most stimulating paper based on the extensive research by Dr Arthur Chung, Richard Majapun, Dr Reuben Nilus, and Frederick Kugan of the Sabah Forestry Department was published. Entitled ‘Insect diversity within the Heart of Borneo in Sabah’, this paper described in detail the ecological significance of insects in the rainforest ecosystem highlighting the importance of the role of insects in the natural world. Such an erudite account of many insect species confined to Borneo Island must provide a stimulus to all young local and budding entomologists.