Few other insects can match the aerial prowess of asilids, which perform with two wings (and a pair of stabilising halteres) manœuvres beyond the means of many other four-winged orders. Only the odonates come close in their mastery of invertebrate airspace and a degree of convergence could be posited in the flies' elongated abdomens, widely spaced eyes that recall those of damselflies and hunting patterns not unlike the habits of perching libellulids. Their legs are also adapted for grasping and like dragonflies, asilids prefer to wing it than walk even a couple of steps to reach a fresh position.
There are species that forage from the ground, grassy thickets or the treetops, but in local woods, individuals can usually be spotted on the sunlit end of a dangling twig or the skeletal tips of dry brushwood by forest trails. Surveying their surroundings for moving targets, the asilids launch unannounced sortees of unreasonable speed that typically end with a return to the same spot, prey in hand, or rather, at the end of a sturdy beak. Larger prey are secured with the aid of spiny forelegs, and even robust bees and dragonflies soon succumb to a cocktail of toxins that first paralyses then pulverises the victim from the inside out.
Robberflies are reputed to possess a 'bite' that causes much pain to humans. But their visual acuity also minimises chances to test this claim. For some reason, robberflies half-an-inch or less in length quite readily endure the antics of digital papparazzi, as long as movements are slow and their seat is unshaken; at Lentang Forest in Selangor, Malaysia, a sleek ommatiine with the plumose antennae that distinguish the subfamily barely budged as it fed on a tiny beetle snared midflight and stabbed in the back.
But a game of hide-and-seek awaits those who attempt to stalk the larger species, which display severely low tolerance for invasions of their personal space. Compounding this frustration are the unruly habitats favoured by some of the biggest robberflies I have seen: mangroves or river banks where the insects easily dash out of sight or at least out of reach even when spotted at an unfair distance. It was thus a pleasant surprise to find at Pulau Semakau a 'giant' which put up with repeated hounding around a scattering of driftwood and slippery rocks that served as its hunting ground. Strongly built with flattened antenna tips and a blue-green shine in oblique light, this asilid favoured flattish surfaces and is possibly a member of the wasp-mimicking genus Pogonosoma. Perhaps assured by the relative immunity it enjoys from avian and other insectivorous predators, the fly chose not to flee to the canopy, making instead short hops from log to log. Our bland attire of greens and greys may have also helped lull the laphrine into a state of complacency and regard us as mere gnats not worth the trouble of temporary evacuation or domesticated pests who cannot survive prolonged exposure on a shore of wild proportions.