Notonecta Backswimmer
( Notonecta sp. )


2012-1023-38CP1309-HET00607-Notonecta_sp[1330h00s,L,A,nrlateralfwd]{EStrand}-G.jpg

PHOTO COMMENT

IDENTIFICATION
Identification:Notonecta sp.
(Linnaeus ,1758 )
Common Name:Notonecta Backswimmer
Life Stage:(A) adult

PHYLOGENY

Phylum:Arthropoda
Class:Insecta
Superorder:Paraneoptera
Order:Hemiptera
Suborder:Heteroptera
Family:Notonectidae
Genus:Notonecta
Taxon Code:HET00607
ITIS/TSN:103558

LOCATION DETAILS
Location Name
Golden Gate Park, Golden Gate Park, San Francisco
County:San Francisco County
ECI Site#:CA38CP0000

RECOGNITION
Description
Genus: Rather large, common backswimmers; eyes more widely separated than in other genera; middle femur with a pointed spine before distal end. Family: Legs: Front legs are raptorial. Front and middle legs are shortened and possess claws. Hind legs are oar-like, with hairs adapting it for swimming, but much longer, and lacking claws. Eyes: Eyes comprise most of the head; ocelli are absent. Antennae: Present but inconspicuous. Mouthparts: piercing/sucking.
Body Length
8-16 mm.
Diversity
17 Species in 4 subgenera in North America.
Similar Taxa
Water Boatmen (family Corixidae). Backswimmers are similar to the Corixidae in overall form. They may be distinguished by their strongly convex dorsal surface which lacks the thin transverse dark stripes and by the form of the foretarsi which are not scoop-like.

BIOLOGY
Backswimmers are aquatic bugs that swim upside-down. When resting at the water surface, the body is typically tilted with the head downward. Setae on the body ventrum form an air gill that traps air and the insect can stay submerged a long time. Backswimmers are predators of small aquatic animals. Prey is seized with the forelegs, the rostrum is inserted and tissue is liquefied and consumed.
Food
Backswimmers feed on mosquito larvae, but also on other insects, aquatic amphibians including frogs and tadpoles, crustaceans and small fish. Setae on legs detect water movement. Prey is seized by forelegs and the insect's rostrum is inserted, injecting enzymes that immobilize the prey while liquefying its internal organs prior to consumption.
Habitat
Ponds, other freshwater pools and slow flowing streams. However, adults fly well and may disperse to new aquatic areas in swarms at night, invading swimming pools by mistake.
Importance
Backswimmers are important as predators in aquatic ecosystems and have some importance as control for mosquitoes, feeding on the larvae; but they also prey on beneficial species. Like many aquatic insects they employ an air gill to breathe underwater. The air gill is located where three longitudinal rows of setae on the insect's ventral abdominal surface trap air at the water surface. Carbon dioxide in the bubble diffuses out while oxygen diffuses in. When the bubble is depleted the insect resurfaces to acquire more.
Range
Throughout North America.
Diversity
17 Species in 4 subgenera in North America.
Importance
Backswimmers are important as predators in aquatic ecosystems and have some importance as control for mosquitoes, feeding on the larvae; but they also prey on beneficial species. Like many aquatic insects they employ an air gill to breathe underwater. The air gill is located where three longitudinal rows of setae on the insect's ventral abdominal surface trap air at the water surface. Carbon dioxide in the bubble diffuses out while oxygen diffuses in. When the bubble is depleted the insect resurfaces to acquire more.
Development
Males have a stridulatory apparatus which may be used to attract females and communicate during courtship. Eggs are elongate and cemented to underwater plant stems. Eggs hatch a few weeks after being laid. The first generation of adults appear in July. There may be two generations per year.

CREDITS
Photographer
Erica Strand

References
Genus Notonecta. (http://bugguide.net/node/view/17932). Accessed April 1, 2016. .
ITIS.
Powell & Hogue, California Insects. University of California Press.
Powell & Hogue, California Insects. University of California Press.


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