Predatory Insects in the Garden

 We are all familiar with the house fly, which feeds on decaying organic matter (among other disgusting things), and is pretty much harmless to other insects. However, there are around 120,000 species of flies in the world (many are yet to be discovered) and some of them are accomplished predators. Robber flies are among these; they have extremely sharp eyesight and can fly at high speed, catching other insects in mid air. They have stabbing mouthparts (proboscis) which inject a powerful neurotoxic venom and digestive juices

into the victim, liquifying its innards, which the fly sucks afterwards.

Due to this formidable weapon and the robber fly’s devastating attack speed, not even wasps, bees or spiders in their webs are safe from these aerial killers. Robber fly venom is usually harmless to humans, but if captured they can give an extremely painful bite.

4. Water scorpion

Despite their fearsome appearance and alarming name, water scorpions are actually insects, belonging to the true bug (Hemiptera) group, and completely harmless to humans. However, they are the scourge of small aquatic animals, which they capture with their strong, modified forelegs. Water scorpions are sort of the insect equivalent of a crocodile; they are slow moving ambush predators that snatch any small animal that comes close; mostly, they feed on other aquatic insects such as mosquito larvae and diving beetles, but they have been known to dine on small fish and frogs once in a while.

Although they have wings, their flight muscles are poorly developed and they fly rarely, usually when the ponds or lakes where they live start to dry up and they must find a new residence. As for the long, tail-like projection at the end of their abdomen, it is actually a breathing tube; the water scorpion uses it to collect oxygen from the surface, and can subsequently remain underwater for up to half an hour before it has to breathe again.

3. Arachnocampa luminosa

Arachnocampa is a kind of gnat from New Zealand; as an adult, its only goal in life is to mate, and it doesn’t feed at all. However, its larvae are accomplished predators with a most unusual hunting method, which gives the animal its name (Arachnocampa means “spider worm”). They usually live in the ceiling of dark, secluded caves, away from wind currents and sunlight. The larvae spin a nest of silk (produced by themselves) and hang several silk threads from the cave ceiling, around the nest.

Each one of these threads is covered on sticky droplets of mucus, sometimes loaded with venom. The Arachnocampa larva can glow like a firefly, which attracts flying insects such as moths to the sticky threads and to a horrible end. Once the unfortunate insect is caught, the larva tones down its glow, pulls the silk thread up and starts feeding voraciously on the entangled prey, whether it is alive or dead.

2. Tiger Beetle

Everyone knows that the fastest land predator is the cheetah, which can reach speeds of 115 kms (71 mph) per hour. Compared to this, a Tiger Beetle is a slowpoke; it can only run at a speed of 8 kms (5 mph) per hour. But if we take its size into account, it is actually the fastest animal in the world! If we could run as fast as the tiger beetle, proportionally to our size, we could reach speeds of almost 500 kms (311 mph) per hour! This speed is so extreme that a running Tiger Beetle must stop constantly to locate prey, since its eyes are unable to process visual information at such high speed.

Tiger Beetles feed on whatever small animal they can subdue; they hunt mostly on land, but are also skilled flyers and have been known to catch other insects in the air too. Their sharp mandibles can easily sever the limbs and body parts of other insects, sometimes bigger than the Tiger Beetle itself. There are many species of Tiger Beetle and they are among the most abundant insect predators, being extremely useful to humans as they help control pests. The larvae of these beetles are also fearsome predators, but instead of chasing their prey, they prefer to wait in ambush, hidden underground, and capture any passing insect with their enormous jaws.

1. Antlion

Adult antlions look rather like damselflies, and although some species hunt smaller flying insects, most of them prefer to feed on pollen and nectar. Antlion larvae, on the other hand, are deadly insect predators, and just like Arachnocampa, they have developed a most amazing trick to capture prey. They live in sandy places, where they dig a funnel-shaped pit, cleverly designed so that no insect can climb its steep walls. The antlion then buries itself in the bottom of the pit. Whenever an unfortunate insect (usually an ant) steps on the edge of the pit, the sand collapses and the victim falls to the bottom, and into the antlion larva’s deadly jaws.

Sometimes, an ant will escape the larva and attempt to climb the walls of the pit; in this case, the antlion has another trick up its sleeve; it throws jets of sand to the ant, so that it slips back into the pit’s bottom. Once the antlion larva has secured its prey, it sucks its body fluid with the tooth-like projections of its jaws, and then throws the dry carcass out of the pit.