What’s bugging the insects?

By Shravan Regret Iyer

Bengaluru: Rare insect species are disappearing from the city due to rapid urbanization. Bengaluru is known for its greenery. Nicknamed ‘Garden City’, it has for long been the abode of a wide variety of insects. All that is changing now as researchers find that various species of insects can no longer be seen in the city.

Is this due to rapid urbanization or alteration of the insect habitat?

An ongoing study taken up by the researchers of Ashoka Trust for Research in Ecology and the Environment (ATREE) to monitor urban land use and its effect on insect diversity in Bengaluru, shows that a few species of dung beetle belonging to Gymnopleurus genus and painted grasshopper, scientifically known as the Poekilocerus pictus, a large brightly coloured grasshopper are no longer a part of the urban landscape.

“Dung beetles are one of the important decomposers in the ecosystem. They increase the fertility of the soil by returning organic matter and nutrients to the soil. But, due to marginalization of people and insects, the urban space has lost three amazing species that feed only on goat and sheep droppings manure,” says Dr. Priyadarsanan Dharma Rajan, a researcher from ATREE.

Photo of Gymnopleurus Cyaneus

Bug Story: Even green spaces like Lalbagh and Cubbon park are no longer home to rare species of dung beetles like this one.

The three species of dung beetles that are no longer seen in the urban space are Gymnopleurus cyaneus; Gymnopleurus Miliaris and Gymnopleurus Parvus. The dung beetles are said to bury the dung in the ground at a depth of between a few centimetres to one meter. This process not only helps in increasing the fertility of the soil but, also helps water infiltration and prevents contamination and leaching of soil.

The city has also lost the painted grasshopper that fed on ‘Sodom’s apple milkweed’, scientifically known as calotropis. The researchers found that this insect is hardly seen in the urban space anymore, including Lalbagh and Cubbon Park. They give the disturbance in habitat as the reason. Meanwhile, the researchers adopted many parameters to study the urban land uses and its effect on insect diversity in Bengaluru.

These parameters included studying the insect diversity in vacant residential plots; educational institutions like GKVK, IISc etc., public parks such as Lalbagh and Cubbon Park. The researchers during the study found that in the core areas of the city, a few species of dung beetles were found feeding on cattle dung, human and dog excreta. They also found that the diversity of the insects was affected by the direct human disturbance of the habitat.

While speaking about the other species that have gone missing, the researcher says, “We don’t know what we are losing. Nothing much has been studied about the other species of insects except ants, dung beetles and crickets. Taking up a study on insects species are more in number as compared to other animal species. Understanding each insect and its habitat requires many years of hard work.”


This story was originally published in Deccan Chronicle October 20, 2014, edition.