Encounter: Robber Fly, raptor of the insect world

With the mean looks and businesslike patience of an assassin, the Robber Fly captures its prey on the wing


Robber Fly. The first time I heard that, I thought, "Why does it have such a name?" I learned that they stay on a perch waiting for any unlucky victim to pass by and quickly catch them on the wing, just as highway robbers waylay and attack passing vehicles.


I saw my first Robber Fly quite recently. While birding, something caught my eye. A large insect flew low, carrying something equally big in its legs. As I watched, it landed on a log. I looked through my camera and zoomed for a good look without spooking the insect. The fly-like predator was holding onto a cicada. I wrote it off immediately as a scavenger feeding on dead insects. Only later did I learn the true identity of this mean-looking fly.

Robber fly with its dinner, a Cicada

Robber flies are also known as Assassin Flies -- makes them sound more vicious, doesn't it? Vicious or not, they are voracious eaters, willing to eat almost any insect or small vertebrate that they can overpower, including other Robber Flies! Their hunting strategy is to wait on a perch from where they can scan the surroundings. When some unfortunate insect flies past, the Robber Fly intercepts and attacks it. The victim is then carried off to be consumed at leisure.


Robber Flies, which include around 7,000 species distributed worldwide, are grouped under the family Asilidae in the order Diptera, comprising 'two-winged' flies. They have strong spiny legs which help them grab their prey. Their huge compound eyes help them detect movements quickly. These eyes are protected from the thrashing wings or legs of their prey by outwardly projecting hairs located between their eyes. After pinning down the prey, Robber Flies use their strong and sharp proboscis to inject neurotoxic venom and digestive juices, which immobilize the prey and start liquefying its body from the inside. This slurry is then sucked up by the fly using its proboscis.


Beej adds: Robber Flies deliver painful bites. While trekking in Brahmagiri, Coorg, I made the mistake of using deodorant and then wearing a sleeveless vest while walking the forest trail. For some reason this attracted Robber Flies. I deduced later that the deodorant had attracted a number of flies and other winged insects and the Robber Flies were in hot pursuit of easy targets. Occasionally, the Robber Flies bit me when I tried to fend them away with my hand. The bites turned into fluid-filled vesicles that hardened into bubble-shaped cysts on the skin between my knuckles and refused to go away for many weeks.


Text and photo by Arun Menon

Sundarbans Diary - The Enormous Estuarine Crocodile

Cruising through the backwaters of the Sundarbans in India, Jennifer Nandi marvels at the estuarine crocodile, even as her thoughts turn to the conflict between these fascinating reptiles and the ecosystem's human inhabitants

Estuarine crocodile sunbathing in the squelchy ooze

The plan for today begins with breakfast on board. Once again, to ensure a fairly decent meal, I do what it takes. It is rather surprising that the guide, the camp crew and boat crew have little idea of what standard quality of a meal implies. Nevertheless, all are co-operative and aim to please, which is a wonderful attitude to work with, and so my suggestions of difficult alterations to the breakfast menu are charmingly accepted.

Researchers teach birds: 'Be afraid, be very afraid'

Do all birds possess an instinct to flee predators? Or is this behaviour a result of conditioning? Research on some island birds has shown their inability to recognise mammalian predators. This may offer an explanation into how native species in island ecosystems that have evolved in the absence of mammalian predators may have hastened their extinction. Case in point: the Dodo on Mauritius. Although the bird was large and ungainly with few escape tricks, it may have also been unfamiliar with danger and this may have made it, figuratively speaking, a sitting duck for the rats and dogs and cats that arrived with the first sailors. The presence of this trait in island birds could adversely impact reintroduction programmes of threatened native bird species. Returning these birds into their predator-infested habitats is fraught with peril at the outset. 'Be afraid, be very afraid' is the survival mantra that researchers are now teaching birds. And how? By attempting to mix birds from predator-free areas with birds who know how to recognise predators in an enclosure. Researchers hope that the fearless birds would learn the fear response from their conditioned friends. PhysOrg has more Technorati Tags: conditioning, bird behaviour, research, fear, predator

When a tiger couldn't bear it

The tiger and the sloth bear are two major predators of the Indian jungles. Between them, it's clear who's boss. Some people know that tigers hunt and eat bears. Others don't. And then, there are people who can't bear to think about either possibility. The acclaimed wildlife filmmaker Shekar Dattatri has captured an intriguing and amusing interaction between a tiger and a sloth bear in Nagarahole, Karnataka. Looking into a patch of forest from a watchtower, the filmmaker and his companions (one of whom was wildlife biologist and tiger expert Dr. Ullas Karanth) saw a large male tiger pursued by a sloth bear. Knowing well the equation between the two animals, they expected a bloody confrontation resulting in the end of the bear as we knew it. Instead, what followed was comedy. The tiger lay down, yawned and regarded the bear's threat displays with apparent amusement. Once finished, the bear went away. And the tiger returned to his nap. Grand stuff. And lucky are those who witnessed it and caught it on film. The insight: Tigers, we are led to believe, are not interested in their prey when they are not hungry. That's a good lesson for little children: Eat at mealtimes and never in between. Text and pictures here