What is a predator?

A predator is an organism that captures and eats another (the prey). This act is called predation.

In general, predators share the following features:

• They are usually larger than their prey, or overwhelm their prey by attacking in large numbers like ants.
• Most do not have specific prey and feed on a wide range of animals which, in some cases, they consume in large numbers. Lady beetles for example, can devour several hundred aphids in a day.
• Some are specific, targeting a particular prey group. For example. feather-legged assassin bugs are known to feed only on ants.
• Death to the victim is usually immediately after capture.
• Adults or young may be predatory. In a number of cases the young are predatory but the adults are not. Adults of alderflies or dobsonflies do not eat but their aquatic larvae are fierce predators.

Which invertebrates are predators?

Predation in insects is common. The adults and young of groups such as mantids, dragonflies and damselflies, lacewings, scorpionflies and alderflies are entirely predacious. Even some moths, a group dominated by plant-feeding species, will bear offspring that are voracious predators.

There are also many non-insect invertebrates that are predators. The main group being the spiders, which are specialist predators. Spiders exploit an immense diversity of habitats and have developed some of the most sophisticated trapping and hunting techniques of any animal group. Other predatory invertebrates include scorpions, centipedes, predatory mites, predatory snails and slugs, nematodes and planarian worms.

What do invertebrate predators feed on?

Invertebrate predators usually feed on other invertebrates, however some feed on fish, frogs, small mammals and birds, in the case of certain large spiders and centipedes. Generally, predators kill to feed themselves but in some cases they hunt for their offspring. Wasps and ants primarily feed on plant liquids as adults but their offspring require solid foods. The adults capture prey and deliver it to their young.

Invertebrate predators usually eat their prey while it is still alive. They do this either with biting and chewing mouthparts or by piercing the body and sucking out the victim's internal fluids. The latter may also involve injecting a cocktail of salivary secretions that act to paralyse the prey and liquefy its tissue.

How do invertebrates capture their prey?

The methods by which invertebrate predators catch prey are incredibly diverse and in some cases very complex.

Invertebrate predators are either passive or active:

• Passive predators tend to sit and wait for prey to come close. Mantids wait poised for long periods of time for prey to come within the grasp of their powerful forelegs.
• Active predators are those that search or hunt for their prey. Dragonflies and Robber flies use speed and agility to pluck prey from the air, while some spiders construct casting nets that are thrown over prey as they fly past.

Some active predators specialise in capturing and eating other predators. The Fringed Jumping Spider specialises in eating other spiders. It will vibrate the web of the intended prey in an attempt to imitate a victim caught in it. The web-building spider comes to investigate what they believe is food, to find they themselves are on the menu.