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Coleoptera
BEETLES; WEEVILS; FIREFLIES; LIGHTNINGBUGS; GLOW-WORMS; JUNE BUGS; BORERS; LADYBIRDS; LADYBUGS
Life   Insecta

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Platyphora haroldi
© Don Windsor, 2005-2008 · 1
Platyphora haroldi
Dynastes tityus, Eastern Hercules beetle, female
© John Pickering, 2004-2023 · 2
Dynastes tityus, Eastern Hercules beetle, female
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Overview Beetles are an incredibly diverse group of organisms. More species of beetles have been found than for any other group.

With a conservative estimate of three million species, Coleoptera is the largest order of insects on the planet. This makes up at least half of the living species on Earth. Coleoptera also has the highest diversity including some of the largest insects like the living Hercules beetle,Dynastes hercules. The name Coleoptera means "sheathed wing," referring to the hardened and thickened fore wings which are used as a sheath to cover the more delicate membranous hind wings. Because of the hardened wings, beetles have a much better fossil record than most other insects. The first fossil record of beetles dates back to the Permian.-- (Berkeley Musuem of Paleontology).

Identification


Beetles have many distinct features, but the most prevalent is the hardened fore wings from which their name is derived (koleos - sheath, pteron - wing). These hardened wings, or elytra, are used to protect the delicate hind wings as well as the abdomen. This protective layer may help them exploit narrow passageways in their habitat (for example, in leaf litter and under bark). Many Coleoptera use their hind wings for flight by opening their elytra just enough to extend the hind wings which are folded under the elytra in a complex manner. Other derived characteristics include uncommon body segmentation. Unlike the common head / thorax / abdomen segmentation, Coleoptera's hind two thoracic segments are joined with the abdomen. The abdomen also houses the retracted genetalia. Coleoptera usually have biting mouthparts and a gula present on the undersurface of the head. Antennae usually have eleven articles.--(David R. Madison, University of Arizona).


Coleopterous larvae contain a head, three thoracic segments, and usually eight to ten abdominal segments. Younger larvae may even possess three pairs of small thoracic legs. Pupation usually occurs in a cavity in the earth or near the feeding place. Some species however form cocoons made from fragments of earth or wood slightly cemented together. The pupal stage lasts about one to three weeks. The insect, once emerged, is at first soft and almost colorless. After a few days it begins to gain its color and its elytra begins to harden (Sharp 1922).


The Adephaga "may be most easily recognized by the development of the hind coxae which separate the first visible abdominal sternum. In the other suborder (Polyphaga), the hind coxae do not completely separate the first visible abdominal sternum. In addition to this feature, Adephaga usually have the hind trochanters particularly well developed and projecting free from the femur. In Polyphaga the hind trochanters are usually less conspicuous. The presence a well developed notopleural suture, while more difficult to appreciate, will identify this suborder. This suture is absent in Polyphaga."-- Eddie Dunbar, Berkeley (2)