Insects and Spiders in a Urban Setting

The human race has managed to subdue and master many animals in the world but insect species is the one that has escaped this fate. Despite this in the last half a century or so the population of insect species has started to decline as an indirect effect of what we have managed to do to the environment.

"Bugs", as most insects are commonly referred to by most people are ubiquitous and by far the largest animal species in the world, 1.5 million named species, and many more unnamed. Many people are afraid of them, some are disgusted by them and a mere Cockroach in the kitchen sends the cook hop on to the dining table! I read somewhere that the only species to survive a nuclear explosion would be a Cockroach, I feel that there may be many more species of insects that may survive.

Taken in isolation, there are good insects that are beneficial and the bad insects, that cause harm.

Some 'bad' insects bite causing discomfort, pain, or burning, some may cause local swelling in the form of a weal, or a severe uncontrolled swelling of the face and airways (angio-neurotic oedema)resulting in breathing difficulties and sometimes even death. Some insects spread diseases like Malaria, Dengue, sleeping sickness etc by carrying the causative parasite in their blood. Locust swarms are known to destroy acres of food crop in a short period and have been responsible for famines throughout history. The insects thus gain economic importance.

The 'good' insects produce Lac, wax, honey, silk, pollinate and produce food grains that nourishes us, fruits that we enjoy, flowers that we rejoice. Some insects are a source of dietary protein to many people in the far east. Some of the 'good' insects also act as pest controllers like the lady Bug eating Aphids.

There are also a large group of insects that act as scavengers by eating decomposing animals and plants cleaning the environment.

Most importantly the insects form a vital link in the food chain. Amphibians and birds eat insects that destroy crops, the birds in turn help spread the seeds of fruits over a vast distances of more than 300 kms , even across the seas (1). Thus if there are no insects our agricultural produce declines and the bird population decreases.

Some species of insects are beautiful to look at with amazing display of colours. Ladybugs are the most common beautiful insects. The butterflies and moths are fine examples both when they are caterpillars and as adults. Some of the others of note are Dragon flies, Grass hoppers, Mantis, Beetles and even some Flies and Bees.

Driving on Motorways in late evening or early morning in UK during the early 70s at 70 miles an hour is a unique experience in more ways than one, at the end of a 100 mile drive the windscreen, headlights and number plates were splattered with insects hitting the car. The insects on the windscreen was washed away intermittently by the washer wiper for better vision, but the number plate and headlamps were washed when you got home.

Concern for the dropping population of birds prompted an interesting study by the Royal Society for Protection of Birds (RSPB) in June 2004 involving around 40000 motorists (2). The study was called ‘Big Bug Count’, the number of ‘splats’ were counted using a cardboard grid – dubbed the ‘Splatometer’.  The results showed that there was only one ‘splat’ every five miles, this surprised many participants. Another study result published by Daily Mail in July 2014 (3) confirmed that insect population has fallen by 45% in the last 35 years while the human population has doubled during the same period.

Reduction in the population of insect can have very wide and far reaching effect on human race as Insects play a vital role in pollinating crops (75% are pollinated by insects) and pest control. The decrease in insect population will also have an effect on the amphibian population that keep the water free of Algae

The quest for ‘green energy’ or renewable source of energy has lead to huge investments in Solar and wind energy. To produce 1mw power by solar energy you need approximately 5 acres of land to be covered by solar panels and the infrastructure. Except in arid areas and desert like environment the solar panels will cover the ground and prevent plants from growing hence this will have significant effect on local insect and bird population, bird population is also affected by the heat reflected by the solar panels. Protagonists of wind energy claim that the effect of windmill on bird population is insignificant, they do accept that in areas that have a high density of birds the effect may be significant.

Thus the dependency of humans on crops and clean water  can be adversely affected to a certain extent by the decrease in insect population and hence the birds and amphibians.

Around one million species of insects and Fifty Thousand species of Spiders have been identified around the world. Around 250 thousand species of Beetles and a similar number of Moths form a large chunk of insects. Approximately 10000 species of Butterflies have been identified around the world. Because of varied topography a large number of these species are found in  India; 50000 species of Insects, of which Butterflies account for about 1500 species, moths account for 10000, species, Beetles for 17500 species. Of the 50000 species of spiders found worldwide India accounts for an estimated 1600 species. New species are added to the numbers every year, unfortunately some species have become extinct and some are on the endangered list with rapid deforestation and urbanisation. In a recent survey conducted in UK indicated that the insect population is decreasing. In UK, the number of beetles, butterflies, bees and wasps has fallen by 60%.

Recent studies have also shown a decline in population of spiders with the increase in temperature and urbanisation

Species Worldwide India
Birds 10245 765
Insects 1 million 50000
Butterflies 18000 1500
Moths 250000 10000
Beetles 350000 17500
Spiders 50000 1600

Some very colourful butterflies and other insects and spiders are still visible in an urban setting in Bangalore. I have had the privilege of identifying and photographing a few in the last few years. I wonder if these species will survive the rapid urbanisation and temperature change.
Sandor Csoori in a poem 'I believed then' has referred to May Beetles as ...........................death doomed guests of the universe;...(5) ; I am sure most of the insects will become '..death doomed guests of the universe..' if we continue our pillage of nature and use of pesticides.

  1. QQuoted in NATURAL SCIENCES : Life Sciences, March 21 2016 09:37
  2. QRoyal Society for the Protection of Birds (RSPB) September 1, 2004
  3. http://www.dailymail.co.uk/news/article-2704973/Insect-population-45-just-35-years-Scientists-fear-drop-harm-planet-vital-role-play.html
  4. QJournal of Entomology and Zoology Studies 2014; 2 (6): 336-339
  5. QInsects, Man and Environment: Who Will Survive?, Joop C. Van Lenteren (https://link.springer.com/chapter/10.1007%2F978-94-011-2904-6_12#page-2)