By Invite, Maneka Sanjay Gandhi

The rich have more of everything. And that includes insects as well!

A recent study done by entomologists, from the North Carolina Museum of Natural Sciences and North Carolina State University, on indoor arthropods (insects, spiders and crustaceans), sampled 50 randomly selected homes in Raleigh, North Carolina, that covered the region's economic spectrum. They collected 10,000 specimens. They discovered that the wealthier the household and its surroundings, the more types of insects it had. The insect biodiversity within the house is part of ecological phenomenon known as the “ luxury effect” – the richer the area, the more bugs in the home. The team, led by California Academy of Sciences postdoctoral researcher Misha Leong, thought that arthropod biodiversity — the number of types of species found within a given dwelling — would increase, based on a home's square footage and the density and diversity of plants outside. But another factor ended up being almost as predictive of a large number of bug species types: neighbourhood income.

The signal was so strong that Leong ran the numbers again and again just to be sure. The data was analysed in every possible way, but the answers were the same. Even homes with relatively light ground cover outdoors had more diverse arthropods inside when they were in wealthy neighbourhoods. In fact, now statistical models based on size of the house, local plant diversity, your monthly income, average neighbourhood monthly income, can give you the number of insects/species you are likely to have. The luxury effect — the more affluent the area, the more diverse its animals. (Last year biologists found that the higher a household’s income, the higher the number of lizard species that could be found there.) While poorer homes had less than 50 species, the richer ones had over several hundred kinds of insects. This included different families of spiders, centipedes, ants, flies, beetles, booklice, moths, springtails, silverfish, gall midges, pillbugs, scuttleflies, dustmites, aphids, slugs, crickets, ladybirds, wasps, bees and cockroaches. Cobweb spiders, carpet beetles, ants, gall midges and book lice were found in 100% of houses samples. The ecologists identified 579 species, with anywhere between 32 and 211 different species, per household. The only insects that they did not find in rich homes were bed bugs and fleas (and much fewer cockroaches)

This increased diversity could be because outdoor species take a liking to the leafier suburbs and then move indoors.The word “luxury effect” was first used for urban houses, suggesting that bigger gardens and disposable income resulted in more diverse species of plants. Raleigh’s indoor insects is obviously a cascade effect in which increased greenery means more outdoor diversity, some of which finds its way indoors.

Higher income households have more access to gardens and indoor plants. And with these plants comes an entire array of harmless insects, the ladybug, the praying mantis, lacewings, leafminers and spiders. Domestic gardens play a vital role in supporting urban insect biodiversity, despite their small size. A paper assessing the abundance, diversity and distribution of insects in urban domestic gardens in the tropics, through a 2013 study in the city of Bangalore, was conducted. Fifty domestic gardens were studied. 2,185 insects from 10 orders, of which ants, bugs, beetles and flies were the most common, were recorded. The number of insect orders encountered was significantly related to the number of tree and herb/shrub species.

The common sense explanation is that every living being goes in search of its specialized food. The wealthy announce their prosperity by filling their houses with furniture, paintings, objects d’art, carpets, toys, hangings, books etc. Each one of these provides food and shelter to different species. A carpet seen under a microscope has thousands of bugs of different species that chew on the fibre, the gum, the matting and each other. Books and glue bring book lice and silverfish – especially when they are not dusted regularly. Fruit and food on kitchen counters bring ants and flies, and flies bring lizards. Paintings, high ceilings and the back of fridges attract spiders. With each insect comes its predator. Beetles arrive. Centipedes are predators of silverfish, beetle larvae and cockroaches. Windowsills, the edges of floorboards, oil droplets in kitchens, the back of closets – all of these are rich veins for finding insects, both living and dead. No matter how much you seal off your house to the outdoors it is very easy for tiny things to find their way in.

Rich households have stocked pantries of cereal, flour and rice. These rations attract weevils and beetles and sugar ants. Rich family children, who study in boarding schools, bring home lice. Cupboards full of clothes attract moths and crickets. Most species are harmless – doing our dirty work. Carpet beetles eat dead insects, spilled food even nail clippings. Dust mites are tiny vacuum cleaners eating dead skin cells. Spiders are actually an effective predator in the garden and most of them are inoffensive. Lest you suddenly feel an urge to vacuum your home, to rid yourself of your invisible insect squatters, let me assure you that most species are completely harmless .A common misconception is that all insects in the house are pests – in fact less than 2 % of the world’s insects are harmful.

My house must be the wealthiest in Delhi if one judges the number of insects and other creatures that share my home. My garden is now a mature forest ecosystem and so the insects come freely in and out. My desk has a small spider who nestles in the rising mound of papers but comes out when I sit down, just to say hello. We don’t use any chemical cleaners in the mops. Mosquitoes stay out because I use gobar ka dhoop every evening. But they lay eggs in the pond outside, which the gambusia fish eat greedily. We have wasp hives, birds’ nests, pigeon homes, owl groves in the trees. I find centipedes, spiders, slugs and large ants in the bathroom, which we put back into the garden. Earthworms come out when it rains. I have an endless number of tiny roommates which fascinate my granddaughter, who is learning from me not to step on ant nests and to examine how cunningly they hide their entrances with bits of chopped grass. Ecologists spend most of their time studying far-off, exotic places, but rarely think about the wildlife inside our homes. We’re actually surrounded by wildlife when we’re indoors. You spend 90% of your time indoors, but you know little about the ecology of the habitat you have created for yourselves. Even houses that look clean, still have lots of insects.

There are only two beings I have zero tolerance for: ticks and termites. My books, letters and family photos, and at least four incomplete book manuscripts, have been eaten by them. At the moment my house is being broken down room by room to make it termite proof. As for ticks, I have seen too many dogs die of tick fever to know that these beings are even worse than mosquitoes, because they are not even in the food chain: no other insect will touch them.

There has always been a mistaken, and yet powerful, association between insect-free cleanliness and respectability. Now you are being judged by the insects. Are you rich enough for them to grace your house?Maneka Sanjay Gandhi