Common name: Crawling water beetles
Number of species: 19
Size Range: 2-5mm
Tarsi: 5-5-5.
Description:
A family of 19 small (3-5mm) yellowish water beetles of slow-moving or static lowland waterbodies. Adults are roughly elliptical, partly carnivorous, and swim clumsily by using the legs on each side alternately. When not swimming, they can be distinguished from other water beetles by their large, flat hind coxal plates, which are used as air reservoirs. Larvae feed on algae and duckweeds, and consequently have specialised mouthparts which distinguish them from the carnivorous larvae of other groups.
Habitat
aquatic, prefer standing water such as large ponds that have no shade and plentiful algae
Season
adults year-round, larvae: spring
Food
larvae feed entirely on algae, either the filamentous forms such as Spirogyra, or macroalgae such as Chara
adults feed on oligochaet worms, small crustaceans, hydrozoans, the eggs of midges, and algae
Life Cycle
overwinter as adults in permanent standing water
Remarks
adults periodically come to the surface for air, which is stored in bubbles under the wings, at the tail, and under the coxal plates – allowing the beetle to breathe underwater for long periods; adults swim slowly and clumsily by moving their legs alternately (rather than in unison like predaceous diving beetles do)
Haliplidae Aubé, 1836 (Crawling Water Beetles)
Haliplids inhabit a large variety of freshwater habitats including a few species that are found in brackish water. Haliplidae are strictly aquatic in the larval and adult stage, and most species live in stagnant or slow-running water. Some species (e.g., Brychius) require clean and oxygen-rich running water. Most species prefer waters with filamentous algae or characeans. Haliplidae are distributed in all major zoogeographic regions (except Antarctica, New Zealand, Oceania) with five recent genera currently formally recognized: Haliplus (worldwide), Brychius (Holarctic), Peltodytes (worldwide except Neotropics and Australia) (Figure 39.17), Algophilus (South Africa), and Apteraliplus (North America). The generic status of Apteraliplus and Algophilus is doubtful, and they are probably closely related with a subgroup of the largest genus Haliplus (Beutel and Ruhnau, 1990; Beutel et al., 2006); however, they are still recognized in the latest world catalog (Nilsson and Van Vondel, 2005). Approximately 238 species are described; interestingly, the species richness is low in tropical zones where they are seldom collected (Van Vondel and Dettner, 1997; Van Vondel, 2005; Fenglong and Van Vondel, 2011).
Ecology
Haliplidae, or the Crawling Water beetle, gets its name from its poor swimming abilities. Rather than swim, the beetle clings to submerged vegetation and crawls along the bottom of the stream or pond that it inhabits. This slow movement supports the idea that they are herbivores in all life stages, although it has been thought that the adults were partially carnivorous. Haliplidae diet preferences are varied based on species. For example, diets can range from a mixture of chironomid eggs, oligochaet worms and small crustaceans, to hydrozoans, algae, characeans and seed-baring plants (3).
Found most commonly in temperate regions (1).They can be seen in calm waters, the adults, larvae, and pupae are found within the same habitat. When threatened at all, they immediately dive straight down, and cling and burrow on the water bottom. Most Haliplidae prefer standing water such as large ponds or slow moving freshwater streams with no shade and high algal growth (1).The Crawling Water beetle can be used to control water plants that have become pests. Agasicles hygrophila, an alticine Chrysomelidae, was introduced into the USA from South America to control Alligatorweed (Altexrnanthera) (4).
The adults range in size from 2.5-4.5mm, and have beautiful spotted shells with uniform rows of black punctures. Their colors range from brown/orange, to yellow/green. Their backs are boat shaped, coming to a point at the rear, and are extremely convex. An easily identifiable feature of this beetle is its ventral view. All Crawling Water beetles possess the characteristic of a flattened sternal ridge, running from the prosternum down to the abdomen. And, they have the fairly uncommon feature of metacoxal plates that cover their basal segments, and the first 2 segments of their legs. The abdomen is comepletely shielded by these features. These plates assist adults in storeing oxygen obtained at the surface in three places; under the wings, at the tail, and under the large coxal plates. This allows the beetle to breathe underwater for extended periods of time (2). They also have protruding eyes and filiform antennae with 11 segments, and their basal antennae are unusually short. Unlike most water beetles, the haliplids are able to remain active through the winter. They congregate in deep water among aquatic plants and where air bubbles collect under the ice (1).
The larvae of this beetle vary widely in appearance, with some species having many spine-tipped filaments radiating from the body, giving it the appearance of a small water porcupine. Other species have no filaments at all. All larvae have some form of forks or teeth on their legs or basal abdominal segment.
