What are arachnids?

Arachnids are arthropods including spiders, scorpions, ticks and mites.

How they differ from insects

Most adult arachnids have four pairs of legs, whereas adult insects have three. They lack antennae and differ in body organisation and mouthparts. Some spiders spin capture webs; others actively pursue prey. Scorpions, ticks and mites have very different lifestyles. It is wrong to assume every spider is dangerous to people: species, location and contact matter. Avoiding contact with unknown animals and seeking expert identification is sensible.

Ecological roles

Many spiders hunt insects as part of food webs. Ticks are associated with hosts, while some mites have distinct roles in soil or on plants. Identification uses body form, behaviour and habitat as well as legs. Pesticides and habitat change can alter relationships between predators and prey. A broad group name does not establish whether an individual species is harmful or beneficial.