If you should take a walk along one of the quieter roads of Besant Nagar, the ones with vegetation-covered grounds and houses with gardens look closely at the ground as you walk. You may find a charming insect, almost round in shape and about the size of a five-rupee coin. It is black, with white spots on it, and if you stop and look around, you are likely to find more of these animated, circular dice about. The creature you have chanced to meet is popularly known as the Seven-spotted Cockroach. It is called so because the number of white spots on the wings of this insect is always seven – four on the left wing and three on the right. It is also found in other parts of Madras, such as Guindy National Park and Tambaram.

It is most readily observed in the months that follow summer, particularly in August. If it has rained in the night and the ground is wet, you have the ideal conditions under which to go Seven-spotted Cockroach hunting. Under such conditions, small groups of these spotted delights come out into the open from leaf litter. They are fairly sedentary, but should you wish to photograph them, you will find them rather tiresome, fidgety subjects – they have a habit of wandering off just when you have everything focussed and are ready to shoot. On the whole, they are one of those creatures that appear to lead quite aimless lives.

To find out more about the Seven-spotted Cockroach, I looked up the trusty Indian Insect Life by H. Maxwell-Lefroy and F.M. Howlett. This solid book of 800 pages was published in 1909 and covers our insects as well as a single book can. Apart from its impressive scope, ‘Lefroy’ is remarkable for its beautiful illustrations, many of them in colour. Surprisingly, this book did not mention the Seven-spotted Cockroach. There was a reference, however, to an insect by its scientific name alone, which I believed was the one of my interest. “Corydia petiveriana (Linn.),” said Lefroy, “is a beautiful cockroach of South India, the tegmina having large white spots” – nothing more. This was intriguing. Was Corydia petiveriana the scientific name of the insect known to us as the Seven-spotted Cockroach? I suspected so, but, vexingly, there was no illustration to clinch the issue.

When I found a flattened but readily identifiable Seven-spotted Cockroach on the road, I collected it and put it in an envelope, after wrapping it in protective layers of leaf. I showed it to various people and asked them whether they knew its scientific name, but no one was sure. In the end, the matter was resolved in Bombay at the Bombay Natural History Society. There, Naresh Chaturvedi, who was then the Curator, took a look at my specimen and then brought out a case containing cockroach specimens. Several Seven-spotted Cockroach specimens were pinned there, labelled Corydia petiveriana. So the two names referred to the same insect! Chaturvedi pointed out to me the variations found in the shape and size of the white spots of this cockroach.

Though the term “cockroach” brings you the image of the common household species, it is used to refer to any member of the family Blattidae. Many of these, like the Seven-spotted Cockroach, are free-living and are not found in houses: they may be found among fallen leaves, on the surface of the soil, under stones, in grass and on trees and plants. Cockroaches are all scavengers in the sense that they feed on dead animal and vegetable matter. None of them consumes living plant tissue or attacks other insects for food.

The Seven-spotted Cockroach is an exceptional insect in having a “common” or “English” name. Most insects other than butterflies are familiar only to entomologists, so they have a scientific name alone. This is not surprising, as only the largest and the most prominent of all living things have common names: birds, large mammals, venomous reptiles, fish of commercial importance and so on.

Indeed, the Seven-spotted Cockroach is twice blessed, because it seems to have enjoyed a second common name. In the copy of Indian Insect Life, neatly pencilled at the side of the page was the name “Madras Domino Cockroach.” I imagine that a reader, perhaps several decades ago, put together scientific and common names as I did, and wrote these words. So Corydia petiveriana was once known as the Madras Domino Cockroach. This is so much more imaginative than plain “Seven-spotted Cockroach”!

Take your friends out for a walk and show them Corydia petiveriana. When they have admired it, teach them its common name – the one that tells you the name of a city where you can find it!

Postscript: The scientific name of the Madras Domino Cockroach is now Therea petiveriana.