The discovery of groups of beetles capable of exterminating thousands of tadpoles has been made almost by chance. The discovery was made by ecologist Jose Valdez who, together with his team, attempted to repopulate a frog conservation site in Newcastle, Australia. The researchers had thought to fence the area to keep out the predator snakes but had not calculated the possible arrival of perhaps even more deadly but at the same time much smaller predators: the Hydaticus parallelus, “underwater” beetles which attack in groups.
They use tactics of encirclement and attack so refined that out of 10,000 tadpoles introduced in the site, three years later only a handful of frogs remained. The case of predators that are much smaller than their prey is quite rare in the wild, just as it is unusual to see insects like beetles hunting in packs.
On nighttime stakeouts, Valdez and colleagues have noticed the tactics these insects use to surround a tadpole and tear it apart in the shortest possible time, tactics so refined that Valdez himself claims to have been shocked. In addition to attacking the tadpoles, these “diving” beetles lay their eggs inside the Lechriodus fletcheri frog eggs. The insects’ eggs usually hatch within 24 hours of hatching the frog’s eggs.
This way when the insects’ eggs hatch they can then easily attack the tadpoles as soon as they are born. Researchers have noticed that only beetle larvae were capable of killing up to three tadpoles every hour, often leaving their prey only half-eaten by another neighbor.