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<gyrinid.htm> [For educational
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COLEOPTERA, Gyrinidae -- <Images> & <Juveniles> Please refer also
to the following links for details on this group: Gyrinidae = Link
2 Description
Gyrinidae are distributed worldwide with about 262 species known as
of 2000. They are all aquatic.
Diagnostic characters of these "whirligig beetles" include
the middle and posterior legs being modified for swimming; the eyes are
divided into separate upper and lower parts; the metasternum does not have an
antecoxal piece, and first ventral abdominal segment is divided by the hind
coxal cavities. The larvae and adults of all species are predaceous on other
insects and animals. They inhabit
both quiet and slowly flowing water.
Adults are usually, but not always, active during daytime, being quite
gregarious, with masses of gyrating beetles very noticeable late in the
season. They are conspicuous by the
way they swim in tight circles on the water surface. The adults are capable of extended flight
as well as of diving and swimming.
Their structure is modified to produce firmness and a distinct smooth
effect. The last two pairs of legs
are short and flattened, bearing an outer fringe of flattened hairs, which
considerably increases the area and thus gives greater swimming
efficiency. During swimming and
diving, the beetles carry a supply of air in a space underneath the
elytra. Although valuable as natural
control of mosquitoes, they have not been actively used in biological
control. The dults prey mostly on animal food although they are usually
regarded as scavengers rather than predators, by feeding on various insects
that fall into water. However, the
larvae are exclusively predaceous, feeding on the body fluids of almost any
form of animal life available in the aquatic environment that is of
appropriate size. The eggs are laid in heaps and sometimes arranged in rows on the
surface of submerged foliage.
Incubation is about 1.5 weeks. Most species exit the water habitat to pupate. The pupal case that is constructed from a
wide variety of resources, is made by the mature larva either on the ground
or on plant stems or leaves above the surface of the water. There is usually only one generation
annually in temperate climates, with overwintering being as adults. Some gyrinids retreat to mud during
winter, while some remain on the water or fasten to submerged vegetation. = = = = = = = = = = = = = = = References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Arnett, R. H. Jr. & M. C. Thomas. 2001. American
Beetles. CRC Press. Balduf, W.
V. 1935.
Bionomics of Entomophagous Coleoptera. J. S. Swift Co., NY.
220 p. Balfour-Browne, F. 1945.
Ann. Mag. Nat. Hist. 21:
103-111. Regimbart,
M. 1902. Genera Insectorum, Fasc. 1. 12 p. Romey, W. L.
1995. "Position preferences within groups: do whirligigs select
positions which balance feeding opportunities with predator avoidance?".
Behavioral Ecology and Sociobiology 37: 195–200. Romey, W. L. & E. Galbraith. 2008. "Optimal group positioning
after a predator attack: the influence of speed, sex, and satiation within
mobile whirligig swarms". Behavioral Ecology 19: 338–343. Romey, W. L. & D. S. Rossman. 1995. "Temperature and hunger alter
grouping trade-offs in whirligig beetles". The American Midland
Naturalist 134 (1): 51–62. Romey, W. L. & A. C. Wallace. 2007. "Sex and
the selfish herd: sexual segregation within nonmating whirligig groups".
Behavioral Ecology 18: 910–915. |