Hunting the Hunter and Looking into our minds

A beetle larva that waves its antennae to attract amphibians before grabbing them, drinking their body juices and reducing them to a dessicated husk has been discovered by scientists in Israel.

Small beetles and larvae make an ideal toad and frog-sized meal, and these amphibians are well-adapted to stealthily creeping up on them and using a lightning-fast flick of the tongue to turn them into lunch.

But in a rare example of role-reversal, predator has become prey. Writing in PLoS One, Tel-Aviv University researchers Gil Wizen and Avital Gasith have discovered that two species of Epomis ground beetle larvae found in the Middle East, E. circumscriptus and E. dejeani, exploit the very same movements that attract frogs and toads in the first place - by waving their antennae around - only to dodge the predators' attempts to eat them and then grab on to the amphibian themselves. The larvae are equipped with razor-sharp mouthparts, which they use to pierce the amphibian's skin and then drink the body fluids. In some cases they even consume the unfortunate victim's flesh.

The researchers began to study the Epomis beetles in 2007 after finding specimens of the larvae attached to amphibians in the wild. But how this status quo was reached - with what should be the hunter being consumed by the hunted - was not known.

To find out, in hundreds of experiments the research duo placed one or more of the larvae into a tank together with a suitable amphibian study subject and videoed the results. The footage shows the larvae increasing the intensity of their antenna-waving activities as the potential victim approaches. When the amphibian makes a grab, the larva dodges the lunge before parrying with an attack of its own, in some cases grabbing the mouthparts and on other occasions latching on behind the head. With an hour or so the amphibian is dead.

The success rate of the strategy is staggering. Out of about 400 face-offs, the amphibians got the larvae into their mouths only 7 times. But even then only transiently: they quickly spat them out, at which point the larvae promptly turned around and made a succesful attack of their own. In one even more surprising experiment, a toad did swallow one of the larvae, which continued to writhe around in the animal's stomach for a further two hours before it was regurgitated. At this point, apparently unharmed, the larva then make a meal of the toad that had previously consumed it.

This kind of role-reversal is extremely rare. In only about 10 percent of predator-prey relationships in the animal kingdom does a smaller animal eat a bigger one, but these are all active attacks rather than a small creature luring its prey. Wizen and Gasith thing that it could have evolved as a means of anti-predator defence, which has subsequently become the creature's exclusive lifestyle. The amphibians may not have evolved to combat the threat since, compared with the majority of the their food, for which their hunting strategy is highly successful, these beetle larvae are relatively rare...

Inspired by the insect-eating pitcher plant, scientists have created a material capable of repelling almost any liquid, including blood and even crude oil.

Dubbed "slippery liquid infused porous surfaces", or SLIPS for short, the new materials are inspired by a natural phenomenon. Carnivorous pitcher plants catch flies and other insects by crafting a specialised surface that traps a layer of water against itself. This repels the oil on the feet of visiting insects, causing them to slide helplessly into the plant's pitcher of digestive juices.

Harvard scientist Joanna Aizenberg and her colleagues have copied this design, creating a microporous surface made of Teflon to which a fluorine-rich organic inert liquid called Fluorinert FC-70 is added. The liquid spreads out across the surface, coating the Teflon, by capillary action and locks into place within the pores. But as it doesn't mix with oil or water-based substances, any liquids - and even ice - that land on the surface form droplets and slide off. And because liquids are incompressible, the new SLIPS-endowed surfaces remain functional even under very high pressures. The team successfully tested them to 767 atmospheres, which was the highest pressure they could generate in their laboratory.

Critically, previous attempts to build liquid-repelling, high-slip surfaces have been modelled on a different plant: the lotus leaf. This uses a system of tiny pillars to trap a layer of air against the leaf surface, causing it to shed water and dirt. But the system is easily compromised by physical damage and liquids with low surface tension simply displace the air rendering the surface useless.

The pitcher-inspired SLIPS, on the other hand, being based on a trapped liquid rahter than air, do not suffer this drawback and are also far more resilient. In fact, when the surface is damaged it effectively "self-heals" when the liquid flows back into the abraded area.

Consequently, Aizenberg and her colleagues, who have described the work this week in the journal Nature, are optimistic that the surfaces will remain super-slippery and liquid repellent even under extreme conditions. Possible applications include uses in deep-sea drilling rigs, safer fuel transportation, anti-icing coatings and even anti-graffiti measures...