Modern forms

Within Coleoptera there are four suborders:

These suborders diverged from one another in the Permian and early Triassic. This has provided ample time for diversification, leaving the suborders substantially different from one another.


Adephaga

Adephaga is the second largest suborder within Coleoptera, with over 40,000 known species. Among its species are wrinkled bark beetles (Rhysodidae), tiger beetles (Cicindelinae), whirlygigs (Gyrinidae), predacious diving beetles (Dytiscidae), and ground beetles (Carabidae). The phylogeny (evolutionary history) of the group is controversial and various arrangements of the 8 families have been proposed.

The two living families with terrestrial members, Carabidae and Trachypachidae, are sometimes called the Geadephaga; the remaining, aquatic families are the Hydradephaga. The majority of species in the suborder belong to the family Carabidae.

Adephagans are diverse in diet and structure. Most are general predators (the Greek word "adephagos" means "gluttonous"), although algal feeders, seed feeders, and fungal feeders occur. Many lineages have gone down, into caves, while others have gone up, into the rain forest canopy or alpine habitats. The body forms of some have become highly modified structurally. Whirlygig beetles (which get their common name from their habit of swimming rapidly in circles when alarmed), live at the air-water interface, and have divided eyes which can see both above and below water. Several types of ground beetles, in particular the bombardier beetles, are notable for being able to squirt a jet of hot foul-smelling liquid from their abdomens, in order to discourage predators.

Golden ground beetle, Carabus auratus
with prey (an earthworm)
.

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Archostemata

Archostemata contains four small families of mainly wood-eating beetles, including reticulated beetles (Cupedidae) and telephone-pole beetles (Micromalthidae). The larvae are typically wood borers that feed on moist and decaying logs. Members of this suborder are similar to some of the earliest, Palaeozoic beetle fossils.

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Myxophaga

Myxophaga is the smallest suborder of Coleoptera, and contains about 100 described species in four families. The beetles are mostly very small (just a few millimetres long at most), and examples include skiff beetles (Hydroscaphidae) and minute bog beetles (Sphaeriusidae). The members of this suborder are aquatic and are associated with riparian habitats, drift material, or interstitial habitats among sand grains. They feed on algae and have been reported from every continent except Antarctica.

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Polyphaga

Polyphaga is by far the largest and most diverse suborder, containing over 300,000 described species, or approximately 85% of the beetle species so far discovered. The polyphagans display an enormous variety of specialisation and adaptation.

The beetles included in Polyphaga can be identified by the cervical sclerites (hardened parts of the head used as points of attachment for muscles) absent in the other suborders. Aquatic lineages have evolved several times within Polyphaga, with the largest aquatic groups being found within Hydrophilidea and Byrrhoidea.

Polyphaga is subdivided into five series:

Bostrichiformia - 6 families, including Anobiidae (death watch beetles), Dermestidae (skin beetles), and Derodontidae (tooth-necked fungus beetles).

Right: Anthrenus verbasci, a skin beetle.

 

Cucujiformia - 82 families, including Chrysomelidae (leaf beetles), Coccinellidae (ladybirds), and Meloidae (blister beetles). Cucujiformia includes the vast majority of phytophagous (plant-eating) beetles.

Right: Harmonia axyridis, an Asian multicolored lady beetle.

 

Elateriformia - 33 families, including Elateridae (click beetles), Cantharidae (soldier beetles), and Buprestidae (metallic wood-boring beetles).

Right: Alaus oculatus, a click beetle.

 

Scarabaeiformia - 14 families, including Lucanidae (stag beetles), Scarabidae (scarab beetles, and Geotrupidae (earth-boring dung beetles).

Right: male Lucanus cervus, a stag beetle.

 

Staphyliniformia - 11 families, including Staphylinidae (rove beetles), Hydrophilidae (water scavenger beetles), and Histeridae (clown beetles).

Right: Devils coach horse beetle - Staphylinus olens, a rove beetle.

 

 

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Author: Phil Jardine
Last updated: 21st November 2005
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Websites produced by students on the MSc Palaeobiology programme in the Department of Earth Sciences at the University of Bristol for academic year 2005-6