By Alma Cooper
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
(1.06 oz)
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)
Some key physical features:
ectothermic 
; bilateral symmetry .
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
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special 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)
For More Information
Find Dytiscus marginalis information at
Contributors
Alma Cooper (author), Southwestern University.
Stephanie Fabritius (editor), Southwestern University.
