Some insects inflict a painful bite or sting, or make you intensely itchy despite their small size. Normally the discomfort is temporary and relatively minor, but in rare circumstances, the consequences can be serious. Some people experience severe, life threatening allergic reactions to insect stings and bites, while mosquitoes can transmit debilitating diseases such as Dengue and Ross River Fever.
Biting insects use their mouthparts to inflict the damage. Some, such as assassin bugs, are predators that attack only when 'provoked' (e.g. when they become entangled in clothing). Most other biters are blood-suckers that seek us out. When our bodies react to their saliva, we break out in itchy welts.
Stinging insects inflict damage with the other end of their bodies. In effect, they have a hypodermic needle at the tip of their abdomen and they use this to stab and inject venom. Many wasps and bees sting, but they are not aggressive and, like assassin bugs, stings are accidental. Other stinging insects that live in colonies (such as paper wasps, honeybees and many ants), will vigorously defend their nests.
Other insects to watch out for in the garden are hairy caterpillars - children don't call them 'itchy grubs' for nothing. Their long hairs are brittle and barbed and are designed to pierce skin and not come out. The hairs are coated with proteins that cause an irritating, allergic response. Any hairy or furry caterpillars are probably best avoided as many different species can cause itchy reactions on contact. There are even a few caterpillars, such as those of cupmoths, that have brittle spines that can pierce the skin and inject venom. Contact with these caterpillars causes a stinging sensation rather than an itch.
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