A wanderer pauses

Half the morning had been spent traveling. I spent the rest sitting outside my hotel room in Tadoba watching butterflies. A common wanderer (Pareronia hippia) paused briefly on a flower, and I snatched it up in my camera. I liked the transparency of the wings: you can see the periwinkle through its wings. I have a soft spot for it, since it was among the first butterflies that I photographed. But it seems to be a completely unremarkable butterfly. That is, until you find that it belongs to the family Pieridae, otherwise known as the yellows and whites. What is this decidedly blue butterfly doing in this group?

Mimicry is the answer. Across India three butterflies often occur in the same habitat: the blue tiger (Tirumala limniace), the glassy tiger (Parantica aglea), and the common wanderer. The first two are the poisonous milkweed butterflies. They have evolved to resemble each other in marking so that predators who have once had a bad experience with one do not attack the other. They are known as Müllerian mimics. The tasty morsel, the wanderer, tries to cash in on this experience by evolving to mimic the distasteful ones. In the gallery above, the photo on the left is of a blue tiger, and I’ve placed the photo of the wanderer next to it for comparison. This deceptive patterning is called Batesian mimicry.

The fact that the wanderer is a Pierid is clear when you see it with closed wings. The underwing colouration is white with light brown markings. Interestingly, the underwing pattern has evolved under sexual selection, and the upper surface under predation. Ecology shapes biology in such strange ways.

The magnetic tree

Nirgundi, Indrani, Sambhaloo, and a large number of other names in many Indian languages refer to Vitex negundo. So the English name chaste tree seems quite superfluous. It is also inappropriate, considering the number of different pollinators which visit it. Chest tree might be a better name, because of its clinically proven efficacy against colds, flu, asthma, and pharyngitis.

I must have seen this plant many times, because it is supposed to be very common across Asia and eastern Africa, and invasive as far away as the USA. But when I carry a good camera I’m much more attentive. So this was the first time I had paid much attention to this cross between a tree and a shrub. Most were about two meters tall, although I’m told it can grow as high as seven meters. The numerous flowers on the hairy branches were tiny: a few millimeters long. I thought they were appropriate subjects for my fancy new macro lens. Some of these macros showed spider silk threaded through the plant. I took this as a sign that it was visited by such a large number of insects that their arachnid predators found it a good place to hide out in.

The number of butterflies I saw on the first shrub I stopped at was astounding. Many individuals from a variety of species fluttered around. It seems to be even more of a butterfly magnet than the Lantana. My macro lens is not very good for photographing active butterflies. Still, I managed to capture a glassy tiger (Parantica aglea), a somewhat battered grey pansy (Junonia atlites), one of a spectacular flock of the yellow-orange peacock pansies (Junonia almana), a common gull (Cepora nerissa), and a skipper which I can’t identify. There were also several species of wasps and bees, and at least two different kinds of blow flies.

I tried to find the geographical and temporal origins of this plant. Instead found myself looking at the fascinating literature on its invasive qualities. I suppose that the large variety of its pollinators is an essential quality for invasive plants. It makes it easier to find new pollinators in any new geography. I saw it growing on verges around roads in a high plateau in the Sahyadris. The rocky ground, with meager topsoil where it grew meant that it was hardy. It is also fast growing, another essential quality for an invader. It certainly out-competed Lantana camara in this landscape. The few bushes of Lantana I saw were stunted dwarves barely surviving between thickets of Vitex. Since Lantana is viciously competitive, and has taken over landscapes elsewhere, that’s quite an achievement.