Scarabaeidae
The family Scarabaeidae, as currently defined, consists of over 35,000 species of beetles worldwide. This massive group has undergone significant change in how scientists classify it. Several groups formerly treated as subfamilies have been elevated to family rank. Examples include Bolboceratidae, Geotrupidae, Glaresidae, Glaphyridae, Hybosoridae, Ochodaeidae, and Pleocomidae. Some other groups were reduced to lower ranks during these revisions. The Catalog of Life published its list of subfamilies for this article in 2023. These changes reflect a deeper understanding of the evolutionary relationships within the beetle order.
Scarabs are stout-bodied beetles that measure between specific lengths depending on the species. Most are brown or black in colour, but many diurnally active species display bright metallic colours. The antennae of most species superficially seem to be knobbed. The several segments comprising the head of the antenna are, as a rule, lamellate. They extend laterally into plates called lamellae that they usually keep compressed into a ball. When following a scent, such a beetle fans the lamellae out like leaves to sense odours. Many species are fossorial with legs adapted for digging. In some groups, males and sometimes females have prominent horns on the head and pronotum to fight over mates or resources. The largest fossil scarabaeid was Oryctoantiquus borealis with a length of 15 centimeters.
The C-shaped larvae, called grubs, are pale yellow or white. Most adult beetles are nocturnal, although flower chafers and many leaf chafers are active during the day. The grubs mostly live underground or under debris so they are not exposed to sunlight. Many scarabs are scavengers that recycle dung, carrion, or decaying plant material. Others, such as the Japanese beetle, are plant-eaters wreaking havoc on various crops and vegetation. Some well-known beetles from this family include June beetles, rose chafers, rhinoceros beetles, Hercules beetles, and Goliath beetles. These diverse dietary strategies allow them to thrive in temperate and tropical environments.
Several members of this family have structurally coloured shells which act as left-handed circular polarizers. This was the first-discovered example of circular polarization in nature. The structural coloration creates optical effects visible to certain predators and potential mates. Scientists study these shells to understand how biological materials manipulate light waves. The phenomenon occurs without pigments but through physical structure alone. Research into these shells continues to reveal new insights about natural optics and material science applications.
In Ancient Egypt, the dung beetle now known as Scarabaeus sacer was revered as sacred. Egyptian amulets representing the sacred scarab beetles were traded throughout the Mediterranean world. A cartouche of Thutmosis III from Karnak temple of Amun-Ra depicts a sacred scarab. This religious significance elevated the insect beyond mere biology into spiritual symbolism. Artisans crafted detailed representations for burial rites and daily protection. The beetle's role in rolling dung balls inspired myths about creation and the movement of celestial bodies across the sky.
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Common questions
How many species are in the family Scarabaeidae?
The family Scarabaeidae consists of over 35,000 species of beetles worldwide. This massive group has undergone significant change in how scientists classify it.
What is the largest fossil scarabaeid beetle named Oryctoantiquus borealis?
The largest fossil scarabaeid was Oryctoantiquus borealis with a length of 15 centimeters. This specimen represents the maximum size recorded for this extinct species within the family.
When did the Catalog of Life publish its list of subfamilies for Scarabaeidae?
The Catalog of Life published its list of subfamilies for this article in 2023. These changes reflect a deeper understanding of the evolutionary relationships within the beetle order.
Why do some Scarabaeidae beetles have structurally coloured shells that act as left-handed circular polarizers?
Several members of this family have structurally coloured shells which act as left-handed circular polarizers without using pigments. The structural coloration creates optical effects visible to certain predators and potential mates through physical structure alone.
Which ancient Egyptian dung beetle known as Scarabaeus sacer was revered as sacred?
In Ancient Egypt, the dung beetle now known as Scarabaeus sacer was revered as sacred. Egyptian amulets representing the sacred scarab beetles were traded throughout the Mediterranean world.