Dytiscus ("little diver" based on Greek δυτικός, "able to dive" and the diminutive suffix -ίσκος) is a Holarctic genus of predaceous diving beetles that usually live in wetlands and ponds. There are 26 species in this genus distributed in Europe, Asia, North Africa and North and Central America. They are predators that can reduce mosquito larvae.
Dytiscus are large water beetles with a robust, rounded shape and they measure long depending on the exact species involved. The largest, D. latissimus, is among the largest species in the family and its size is only matched by certain Megadytes. The tarsi of the males are modified into suckers which are used to grip the female in mating. Females are usually larger than the males and come in two forms, with grooved (sulcate) or smooth elytra. Males only ever have smooth elytra. The adults of most species can fly.
Life history Adult beetles and their larvae are aquatic but the pupae spend their life in the ground. Females lay eggs inside the tissue of aquatic plants such as reeds. The eggs hatch in about three weeks.
The larvae (known as "water tigers") are elongate with a round and flat head and strong mandibles. They are predatory and their mandible have grooves on their inner edge through which they are able to suck the body fluids of their prey. The larvae take air from the surface of the water using hairs at the end of their abdomen. These lead to spiracles into which the air is taken.
Once the larvae grow to some size, they move to soil at the edge of water and burrow into a cell and pupate.
The adults breathe by going to the surface and upending. They collect air under their elytra and are able to breathe this collected air using spiracles hidden under the elytra.
In Dytiscus marginalis and other species the tarsus of the forelegs is modified in males to form a circular sucker. A reduced sucker is also seen in the midleg of the male.Miall, L. C. (1912) The natural history of Aquatic Insects. Macmillan and Co. Ltd.
Parasitoids Eggs of Dytiscus are sometimes parasitized by wasps of the families Eulophidae, Mymaridae and other Chalcidoidea.Jackson D.J. (1958) A further note on a Chrysocharis (Hymenoptera, Eulophidae) parasitizing the eggs of Dytiscus marginalis L., and a comparison of its larva with that of Caraphractus cinctus Walk. (Hym., Mymaridae) J.Soc.Brit.Entomol. 6:15-22.Jackson D.J. (1961) Observations on the biology of Caraphractus cinctus Walker (Hymenoptera, Mymaridae), a parasitoid of the eggs of Dytiscidae. II. Immature stages and seasonal history with a review of mymarid larvae.. Parasitology. 51:269-294.
Species Dysticus contains the following species:Dytiscidae Species List at Joel Hallan's Biology Catalog. Texas A&M University. Retrieved on 7 May 2012.
Dytiscus alaskanus J.Balfour-Browne, 1944 Dytiscus avunculus C.Heyden, 1862 Dytiscus caraboides Linnaeus, 1758 Dytiscus carolinus Aubé, 1838 Dytiscus circumcinctus (Ahrens, 1811) Dytiscus circumflexus Fabricius, 1801 Dytiscus cordieri Aubé, 1838 Dytiscus dauricus Gebler, 1832 Dytiscus delictus (Zaitzev, 1906) Dytiscus dimidiatus Bergsträsser, 1778 Dytiscus distantus Feng, 1936 Dytiscus fasciventris Say, 1824 Dytiscus habilis Say, 1830 Dytiscus harrisii Kirby, 1837 Dytiscus hatchi Wallis, 1950 Dytiscus hybridus Aubé, 1838 Dytiscus krausei H.J.Kolbe, 1931 Dytiscus lapponicus Gyllenhal, 1808 Dytiscus latahensis Wickham, 1931 Dytiscus latissimus Linnaeus, 1758 Dytiscus latro Sharp, 1882 Dytiscus lavateri Heer, 1847 Dytiscus marginalis Linnaeus, 1758 Dytiscus marginicollis LeConte, 1845 Dytiscus miocenicus Lewis & Gundersen, 1987 Dytiscus mutinensis Branden, 1885 Dytiscus persicus Wehncke, 1876 Dytiscus pisanus Laporte, 1835 Dytiscus semisulcatus (O.F.Müller, 1776) Dytiscus sharpi Wehncke, 1875 Dytiscus sinensis Feng, 1935 Dytiscus thianschanicus (Gschwendtner, 1923) Dytiscus verticalis Say, 1823 Dytiscus zersii Sordelli, 1882
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