The Order Coleoptera (commonly known as beetles) may be subdivided into a numerous number of families. Four of these families include Anthicidae, Dytiscidae (also known as Predaceous Diving Beetles), Haliplidae and Hydraenidae.
The Haliplidae are a family of crawling beetles which consists of approximately 200 species making up 6 genera. They are normally 2-4.5 mm in length and have a width of 1.45-2.5 mm. The beetles are oval ion shape and are yellowish in color. They have a slight head inclination with eyes that are not very protuberant. They have short antennae which have 11 divisions each. Their mandibular prosthecae are very well developed to be able to feed on algae. The mandibles have a channel which is used to suck bodily fluids from the larvae. The haliplidae are found in fresh-water bodies such as slow-moving rivers and streams. They move on the surface of water through ambulatory leg motion which comprises of alternating leg movements.
The Dytiscidae family is one of the most commonly seen and largest groups of water beetles, with some attaining up to 35 mm in length. The family consists of 226 species which make up 42 genera. The Dytiscids have a hard and smooth oval body which does not have a ventral spine. Their hind legs are flattened and have some hairs to aid in movement in water. This is done by paddling. They are found mainly in Australia and are all aquatic. Adults can fly to isolated habitats, allowing them to spread to far-flung regions. They prefer stagnant or slow moving water for their habitat. These include lakes, billabongs, pools, ponds and dams. These beetles require atmospheric air and they have to keep rising to the surface to fetch a bubble of air which they carry in a space beneath their wing covers. They are carnivorous and feed on insects as well as small fish.
The interesting fact about the Haliplidae family of water beetles is that some of its members are critically endangered. For example, the Brychius hungerfordi, also known as Hungerford's water beetle remains precariously on the verge of extinction. According to a publication in 2004, only about 1000 individuals existed in the wild. Although a similar report discovered that their number had not changed much by 2010, 1000 individuals is a very small number for insects, which are some of the most common organisms on earth. Another interesting fact about Hungerford’s water beetle is that, unlike other similar species, it lives in one location (currently along Maple River). Unknown populations may also exist outside the United States but these are not expected to be substantial. The Hungerford’s beetle thrives in 15-25 °C environments especially along alkaline streams.
One major interesting fact about the Dytiscidae family is their adaptation to being carnivorous. Their larvae are referred to as water tigers because they have a gargantuan appetite. The larvae are especially adapted to enable their wild feeding characteristics. Some of the adaptations include their long slender sickle-like jaws whose strength is suited to feeding on other insects and small fish. In addition, these jaws have canals through which digestive juices are channeled from the larvae into its prey. Once the animal tissues of the prey are digested, they are then siphoned to the larvae.