Insects are very close to the bottom of the food cycle, and many end up in the stomachs of birds and other animals. However, many millions also manage to survive to sexual maturity. Let’s look at some of the strategies they use.
Insects employ various strategies to ensure that they survive to sexual maturity and don’t become food for predators. Many species camouflage themselves to look like their environments, such as stick insects and treehoppers. Keeping out of sight is one of the best ways to avoid detection. Wasps and bees sting, while ants have a nasty bite. A toxic, sticky, or foul-smelling compound is also used as a deterrent by many species of insects.
Insects have some of the best ways to avoid detection. Let’s look at a few of these now.
Natural selection plays a huge part in the survival of insects. Charles Darwin observed the peppered moth. These are usually white with black streaks, allowing them to remain hidden while resting on tree bark. However, during the industrial revolution, the plants decayed, exposing sooty tree bark, which was darker in colour.
While darker moths were at one point much rarer, they soon became more frequent. Animals can adapt very quickly to the changing environment, and this happened so that birds couldn’t make an easy meal of the moths.
Natural selection has led to insects of all shapes, sizes, and colours. Many insects have become less noticeable, blending into their environment. Stick insects look remarkably like twigs, while some species of treehoppers and thorn bugs look like the thorns of bramble bushes. Looper moth larvae look like dried twigs, allowing them to blend in while defenceless.
Insects sometimes perfect the colour and shape of the background to which they are attached, and there are many examples in tropical countries. Leaf insects, bush crickets, and some butterflies appear similar to green or dried leaves. The similarities are not limited to their look either but also their behaviour.
Some stay immobile for long periods, but they sway like twigs in the breeze when they do move. Colour and shape also help preying insects to find their food easier without them being seen while also remaining hidden from those hunting them.
Camouflage plays an essential part in survival from ending up as a meal for another animal. While some insects look and act like twigs and branches, others mask themselves with objects from their environment. The assassin bug nymph covers itself with refuse or sand to blend in, while larvae of some beetles cover themselves in their old moults or waste.
Several insects use chemical protection to protect themselves. They produce a toxic, sticky, foul-smelling compound that predators do not like. Some shield bugs and thorn bugs have spines on their bodies which can lacerate the throat of an unsuspecting bird when swallowed. Ants also have a well-developed chemical defence system, giving a nasty bite and sting.
Some insects even have real weapons that they can use when attacked. Wasps and bees have a nasty sting, while bombardier beetles spray out a hot cyanide compound which explodes when it hits the air. True bugs protect themselves using scent glands or by biting.
While some produce chemicals themselves, others will eat poisonous plants so that the poison stays in their bodies to protect them. While being poisonous is helpful, unless the bird knows that the insect is poisonous before they eat it, it will be of little use to the insect in the stomach.
Birds need to learn which insects are poisonous and non-poisonous, and this only happens after they have eaten different insects and learned the hard way which ones are poisonous.
Poisonous insects are often easily recognised by their bright colours. Red or yellow insects are often poisonous, so a bird remembers the colour and associates it with something they shouldn’t eat. For this to work, the insects must be numerous. Every predator or bird has to gain this knowledge through experience and learn to avoid brightly coloured poisonous insects.
If the insect was uncommon, the species might become decimated during the learning period of young birds. Non-poisonous insects, and many other animals, evolve similar colourations and behaviours as poisonous species. Once a predator has had a bad experience with another with the same colour, they will think twice about attacking them.
Many insects mimic poisonous insects with their colours and behaviour, allowing them to avoid being food for a larger animal. Wasps have a dangerous sting for many animals, and their yellow and black colour is copied by many beetles, moths, bugs, true flies, and sawflies.
Many butterflies have long outgrowths on their hindwings and eye-shaped spots at their roots. If a bird mistakes these for antennae and eyes, they may peck at them. The butterfly will then fly off in the opposite direction, surprising the bird. If the bird does succeed in biting the tail on the hind wing, the damage will not be too bad.
The eyes hawkmoth usually rests on tree bark during the day. They fold their forewings over their hind wings, concealing them with a colour similar to the tree bark. If a bird notices them, it may open its forewings to show the large false eyes on its hind wings.
Many butterflies have concealing colours on the undersides of their wings, but the uppersides often have bright colours with false eyes. Many true bugs have red on their undersides, the colour of poison for an experienced predator.
Sawfly caterpillars and prominent moths live in large groups on the plants they feed. If they face danger, they rear up, with their heads or abdomens facing forward. The increased size often scares away predators, but some also have a second defence of bad-tasting plant substances in their bodies.
While many insects use camouflage, chemical protection, and other strategies to keep them safe, most insects will become food for other animals. These strategies need to be genetically linked to give their species the best shot at survival. Insects that are hidden are much more successful than those that do not employ a similar strategy.