Scarabs are beetles in the insect Order Coleoptera. Scarabs belong to the Superfamily Scarabaeoidea named by Latreille in 1802. Worldwide there are around 30,000 species of scarab. Most are in the tropical or sub-tropical regions. There are 99 species on the 2018 Checklist of Beetles of the British Isles by Duff and these are separated into four Families – Geotrupidae (Dor Beetles and Burrow Beetles), Trogidae (Hide Beetles), Lucanidae (Stag Beetles) and Scarabaeidae (Dung Beetles, Sand Scarabs and Chafers). They range in size from 2 or 3 mm to over 70mm.
Like all beetles, scarabs undergo complete metamorphosis and the lifecycle consists of four stages: egg, larvae, pupa and adult. The white larvae or grubs are C shaped with a distinctive brown head capsule and three pairs of legs on the thorax. The length of time it takes to complete the lifecycle varies widely among species. Many have an annual lifecycle but for the Stag Beetle Lucanus cervus it takes several years.
Adult scarab beetles have asymmetrical clubbed antennae that are made up of antennal plates and open up a bit like pages in a book. This is a defining characteristic of all scarabs.
All British scarab adults are capable of flight, although some species do not fly readily. The membraneous wings are folded up underneath the hard wing cases or elytra. This protects the fragile wings from damage when not in use. Some species fly during the day, some at dusk and others at night.
The majority of adult species feed on decomposing matter such as dung, carrion or fungi. Others visit plants to eat petals, leaves and pollen. Often the larvae will have a different feeding niche than the adults. For example, as an adult the Long-lined Decimator Melinopterus sphacelatus, feeds on dung whereas the larvae eat roots in the soil. Due to this wide range of feeding behaviour scarab beetles can be found in many habitats. A few are classed as agricultural pests due to the root feeding behaviour of the larvae but the majority are viewed as beneficial as they help to decompose and recycle organic matter.