Syntelia

The whirligig beetles are water beetles, comprising the family Gyrinidae that usually swim on the surface of the water if undisturbed, though they swim underwater when threatened. They get their common name from their habit of swimming rapidly in circles when alarmed, and are also notable for their divided eyes which are believed to enable them to see both above and below water. The family includes some 700 extant species worldwide, in 15 genera, plus a few fossil species. Most species are very similar in general appearance, though they vary in size from perhaps 3 mm to 18 mm in length. They tend to be flattened and rounded in cross section, in plain view as seen from above, and in longitudinal section. In fact their shape is a good first approximation to an ellipsoid, with legs and other appendages fitting closely into a streamlined surface. Whirligig beetles belong to the beetle suborder Adephaga, which also includes ground beetles and diving beetles.

The telephone-pole beetle is a beetle native to the eastern United States, and the only living representative of the otherwise extinct family Micromalthidae. They have an unusual lifecycle involving asexually reproducing (parthenogenetic) female larvae, as well as non-functional "ghost adults".

Passalidae is a family of beetles known variously as "bessbugs", "bess beetles", "betsy beetles" or "horned passalus beetles". Nearly all of the 500-odd species are tropical; species found in North America are notable for their size, ranging from 20–43 mm, for having a single "horn" on the head, and for a form of social behavior unusual among beetles.

The Lymexylidae, also known as ship-timber beetles, are a family of wood-boring beetles. Lymexylidae belong to the suborder Polyphaga and are the sole member of the superfamily Lymexyloidea.

Prostomidae is a family of beetles with no vernacular common name, though recent authors have coined the name jugular-horned beetles. They are often found in dead wood. The family consist of two extant genera with about 20 species. Prostomis americanus is known from North America. Other species of Prostomis are found in Europe, Africa, the Pacific region and East Asia. Species of Dryocora are known from New Zealand, Australia and Tasmania.

The family Oedemeridae is a cosmopolitan group of beetles commonly known as false blister beetles, though some recent authors have coined the name pollen-feeding beetles. There are some 100 genera and 1,500 species in the family, mostly associated with rotting wood as larvae, though adults are quite common on flowers. The family was erected by Pierre André Latreille in 1810.

Ripiphoridae is a cosmopolitan family of some 450 described species of beetles sometimes called "wedge-shaped beetles". Ripiphoridae are unusual among beetle families in that many species are hypermetamorphic parasitoids, an attribute that they share with the Meloidae. Members of the family differ in their choice of hosts, but most attack various species of bees or wasps, while some others attack cockroaches or beetles. Many species of Ripiphoridae have abbreviated elytra, and flabellate or pectinate antennae.

The Stephanidae, sometimes called crown wasps, are a family of parasitoid wasps. They are the only living members of the superfamily Stephanoidea. Stephanidae has at least 345 living species in 11 genera. The family is considered cosmopolitan in distribution, with the highest species concentrations in subtropical and moderate climate zones. Stephanidae also contain four extinct genera described from both compression fossils and inclusions in amber.

The Bostrichidae are a family of beetles with more than 700 described species. They are commonly called auger beetles, false powderpost beetles, or horned powderpost beetles. The head of most auger beetles cannot be seen from above, as it is downwardly directed and hidden by the thorax. Exceptions are the powderpost beetles, and members of the subfamily Psoinae.

Histeroidea is a superfamily of beetles in the infraorder Staphyliniformia.

Lepicerus is a genus of myxophagan beetles containing three described species in the family Lepiceridae; it is the only extant genus in the family, with another genus, Lepiceratus only known from fossils. Extant species occur in the Neotropics, from Mexico south to Venezuela and Ecuador. Fossils referrable to the genus are known from the early Late Cretaceous of Southeast Asia.

Helotidae is a family of beetles, in the suborder Polyphaga. The family includes about five extant genera, Helota MacLeay, Neohelota Ohta, Afrohelotina Kirejtshuk, Metahelotella Kirejtshuk, and Strophohelota Kirejtshuk. Helotidae are found mainly in the Old World tropics and are absent from Australia and Madagascar. The antennae are clubbed on the final three segments and is retractable within grooves under the head. The wings have reduced venation with just 4 anal veins. Helotids are known to be associated with sap, fruit and flowers, and the larvae of some species are known to bore into wood in order to pupate.

Smicripidae is a family of beetles, in the superfamily Cucujoidea. The common name for this family is palmetto beetles. The family only has one extant genus, Smicrips, with six extant species native to tropical and subtropical regions of the Americas and extinct species from the Eocene of Europe and one extinct genus, Mesosmicrips, known from the mid Cretaceous aged Burmese amber. Smicrips larvae are usually found amongst decaying vegetation, while adults are typically found on infloresences, especially those of Arecaceae (palms), althought associations with flowers of Fabaceae (legumes), Passifloraceae, Bombacaceae and Cactaceae (cactus) have also been recorded. Their diet is unknown.

The Brachypsectridae are a family of beetles commonly known as the Texas beetles. There are only two extant genera, Brachypsectra and Asiopsectra. Brachypsectra has a cosmopolitan distribution, mostly in arid regions, while Asiopsectra is found in Central Asia and the Middle East.

Passandridae, the "parasitic flat bark beetles," are a family of beetles notable for being one of the very few beetle families with larvae that are, as far as known, exclusively ectoparasitic on the immature stages of other beetles and Hymenoptera.

Artematopodidae is a family of soft-bodied plant beetles in the superfamily Elateroidea. They are mostly found in understory forest foliage. The life history of the group is obscure, larvae of the genera Eurypogon and Macropogon likely feed on moss, while the larvae of Artematopus have been fed insect remains.The oldest fossils of the family date to the Middle Jurassic.

Throscidae is a family of elateroid beetles found worldwide with around 150 species in 5 extant genera. The larvae are soil-dwelling, siphoning fluid from mycorrhizae attached to trees. The adults are short-lived, with the adult males being noted for a complex mating dance. Like some other elateroids, they are capable of clicking.

Cyclaxyridae are a family of beetles in the superfamily Cucujoidea. The only living genus is Cyclaxyra, with two species endemic to New Zealand. Other species have been named from fossils. They are also known as sooty mould beetles due to the association of Cyclaxyra with sooty mould. The extant species are mycophagous, feeding on spores, conidia, and hyphae.

Thanerocleridae is a family of beetles belonging to the superfamily Cleroidea. It was formerly considered a subfamily of Cleridae, but was recently elevated to the rank of family. The family has 36 living species in 10 genera, which are found globally, mostly in low-latitude tropical regions, though the genus Zenodosus is found in temperate North America. Thaneroclerid species are likely all predatory both in adult and larval stages. They target small fungus and wood associated beetles, and are generally found in places where such beetles are likely to be found, typically tree associated habitats such as under bark, though some species occur in other locations such as termite nests.