Dytiscus marginalis

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Geographic Range

Habitat

Dytiscus marginalis do not exist below certain elevations and are found in mountain lakes or ponds or in collections of melted snow. Adults hibernate under stones to avoid being frozen in the water during colder seasons. (Evans and Bellamy 1996) These beetles are active anywhere by the ice, where they exploite the oxygen bubbles that usually occur under ice along with dissolved oxygen.(Crowson 1981)

  • Aquatic Biomes
  • lakes and ponds

Physical Description

These aquatic diving beetles have bodies that are compressed top to bottom and keeled laterally and ventrally. They have hydrodynamic bodies and average 27mm in length. (Crowson, 1981; van Nostrand, 1972)

  • Range mass
    30 (high) g
    1.06 (high) oz

Reproduction

Mating occurs in or near water by the Dytiscids. Beetles of this species undergo a complete metamorphosis. Eggs are laid underwater and are usually placed in special cavities cut in the stems of emergent plants (Crowson 1981). Eggs hatch within a few weeks (McCafferty 1998).

Behavior

Their body structure allows them to dive quickly so that they may search in cooler surroundings at times. A digestive structure, the ampullla, contains an unpleasant smelling liquid that the beetle ejects through the anus if it is being seized. The main toxins that this species uses in defense are benzoic acid and various derivatives. (Evans and Bellamy 1996, Crowson 1981)

Food Habits

Beetles of this family eat on several aquatic animals, including fish! Adults and larva are very carnivorous and search for their prey by diving and swimming actively through zones in the water where light reaches. (Borror and White 1970, Gullan and Cranstan 1994)

Conservation Status

European scientists are trying to extend protection to the Dytiscus marginalis beetles and other water beetles by going further than just restricting collection. The Water Beetle Specialist Group and the Saproxylic Invertebrate Project are two organizations that have been hard at work fostering the education, biodiversity, and conservation of the water beetle.

(Evans and Bellamy 1996)

Contributors

Alma Cooper (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

References

Borror, D., R. White. 1970. A Field Guide to Insects: America North of Mexico.. Boston: Houghton Mifflin Co..

Crowson, R. 1981. The Biology of the Coleoptera. New York: Academic Press.

Evans, A., C. Bellamy. 1996. An Inordinate Fondness for Beetles. New York: Nevraumont Publishing Company.

Gullan, P., P. Cranston. 1994. The Insects: An Outline of Entomology. London: Chapman and Hall.

McCafferty, A. 1998. Aquatic Entomology. Boston: Jones and Bartlett Publishers.

van Nostrand, B. 1972. Grzimeck's Animal Life Encyclopedia: Insecta. New York: Reinnold Company.