Please refer also to the following link for details on this group:
Haliplidae = Link 1
Description & Statistics
This family of water beetles swim with an alternating leg motion, but usually move by crawling. There were ca. 205 species in 5 genera identified by 2011. They occur in freshwater habitats. They are also called crawling water beetles.
Adults are usually oval in shape, with a convex upperside. The size ranges from 1.4–5.2 mm long. The color is yellowish or light brown, often with light and dark dots. There are usually 10 rows of punctures on the elytra. The species have large immobile coxal plates on the hindlegs, which are used for storing air and to add to the air carried under the elytra. There are protruding compound eyes and a rather small head, which 11-segmented antennae with a short scapus. The legs bear long swimming hairs on tibiae and tarsi, but are not flattened. The hindwings are not folded under the elytra, but rolled together apically. The larvae have a long and thin body with a tough integument. They also have specialized mouthparts that are carried on a small head. The maxillae and labium are adapted for feeding on algae, while the mandibles contain a channel through which fluids are sucked. The larval legs are short and have a single claw each, but the forelegs are adapted to climbing on aquatic plants. There are gills for respiration. The final instar has functional spiracles on the mesothorax and the first to seventh abdominal segments. The principal habitat is in aquatic vegetation around small ponds, lakes, and still streams. Adults are omnivorous, eating insect eggs, small crustaceans, hydrozoan polyps, and algae, but the larvae eat only algae. There are three larval instars, and pupation is on land in a cavity constructed by the larva.
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Rolf, G. B. February 25, 2008. "Haliplidae. Crawling water beetles". Tree of Life Web Project
Roughley, R. E. 2001. "Haliplidae". In: Ross H. Arnett, Jr. & Michael C. Thomas. American Beetles, Volume 1. CRC Press.
Van Vondel, B. J. 2005. "Haliplidae". In: A. N. Nilsson. Volume 7. Amphizoidae, Aspidytidae, Haliplidae, Noteridae and Paelobiidae (Coleoptera, Adephaga). World Catalogue of Insects. Stenstrup: Apollo Books.