The Salty Surfer

Kelly’s Field Notes

Common Name: Water Striders, Water Skimmers, Water Skaters, Water Skippers, Pond Skaters, Puddle Flies, Water Bugs

Order: Hemiptera

Family: Gerridae

Genus: There are currently 67 described genera.

Species: There are over 1,700 species of water strider (Gerrids)!

Notable species:

• North American Common Water strider (Aquarius remigis) - found throughout North America, coast to coast! 

• River Skater (Aquarius najas) - commonly found throughout western and eastern Europe, into the Mediterranean.

• Water striders of genus Halobates are called sea skaters or ocean striders. Halobates are found in the Indian, Atlantic, and Pacific oceans. Sometimes along the coast but also in open water. This genus is the only insect found in the open ocean! We have a fossil example of a species (H. ruffoi) from Verona, Italy. This little critter lived 45 million years ago. 

Description: 

Water striders have elongated dark brown or black bodies, typically from 2 to 20 mm in length  (0.08-0.8 in). They use their long, hydrophobic legs to distribute their weight evenly across the water's surface, keeping their bodies out of the water. Water strider legs are covered with microscopic hydrophobic hairs (setae), which trap air and repel water. This allows them to remain buoyant and avoid breaking the water’s surface tension. The largest species, Gigantometra gigas, has a body length of 35 mm (1.4 in) with an overall leg span of 300 mm (1 ft)!

The mesothoracic (middle) legs are used for propulsion, while the prothoracic (front) legs are shorter and used for capturing prey. The metathoracic (hind) legs aid in steering and stability. They are like small boats on the water with legs working as oars, rudders, and fishing poles.

Some species exhibit wing polymorphism (different wing sizes within the same species). Water striders living on gentle ponds have longer wings, capable of soft lift and flight. However, water striders living in fast moving water have smaller wings, which take less damage in rough conditions. Some forego wings altogether! All species under all circumstances of our marine dwelling friends, Halobates, are wingless. Halobates also have squattier broader bodies than their freshwater cousins, this adds stability on the rolling open ocean.

Life Cycle: 

Female water striders can physically block males from mating with them by keeping their genital opening closed. To get around this, males will climb on top of the female and slap the water to potentially attract predators. The female, now under water and in danger, has to decide if it’s worth the risk to continue not being receptive. 

When it’s time to lay eggs (between 1 and 20 per laying event), she will attach them to submerged rocks, vegetation, or floating debris. It only takes a week or two for the eggs to hatch. When we welcome them into the world, the tiny water striders look like miniature versions of their parents. As a true bug, there is no pupal step, they go from egg, to nymph, to adult. It typically takes 5 molts to get to adulthood and plenty of eating. Both nymphs and adults feed on small invertebrates, both living and dead.

The marine water striders (Halobates spp.) eat zooplankton, insects that have fallen into the water, dead bits off of larger animals —such as jellyfish—, and fish larvae and eggs. 

Water strider adults live for a few months, until it gets too cold for survival and they die off. Young that hatch late in the summer or early in the Fall overwinter along the shoreline until the weather warms up again.

Other Striders:

Please note, these are not the only “bugs” boating around on the water’s surface! A few other examples are the shortlegged striders (Family Vellidae), waterboatment (Family Corixidae), and water treaders (Family Mesovelidae). Beetles have also taken to water sports in the form of whirlygigs (Coleoptera: Gryinidae).

Super Powers:

• Water striding - whether it’s freshwater or saltwater, these guys can skate across the water by not breaking surface tension.

• Super Speed Skimming - water skimmers have one of the fastest speeds on water relative to their body size. Capable of moving 1.5 m/s! That would be equivalent to a human running 100 m/s.

• Sensing Vibration - water striders are very sensitive to picking up vibration on the water’s surface. This alerts them to both predators and prey.

• Leaping - to escape predators, water striders can leap into the air! Check out this video from the New York Times - https://www.youtube.com/watch?v=MsD8wahyRq8

• Flight - water striders can fly and occasionally do, to escape predators.

References:

Cheng, Lanna. "Biology of halobates (heteroptera: Gerridae)." Ann. Rev. Entomol, 1985.

“Family Gerridae.” Australian Department of Climate Change, Energy, the Environment and Water, biodiversity.org.au/afd/taxa/GERRIDAE.

“Gerridae.” Wikipedia, Wikimedia Foundation, 20 Sept. 2019, en.wikipedia.org/wiki/Gerridae.

“Gyrinidae.” Center for Freshwater Biology, University of New Hampshire, cfb.unh.edu/StreamKey/html/organisms/OColeoptera/FAco_adult/FAGyrinidae/Gyrinidae.html.

“Halobates.” Wikipedia, Wikimedia Foundation, 14 Dec. 2023, en.wikipedia.org/wiki/Halobates.

“Species Spotlight - Water Striders.” U.S. National Park Service, 2015, www.nps.gov/articles/pecies-spotlight-water-strider.htm.

“Water Striders.” Field Guide to Common Texas Insects, Texas A&M , texasinsects.tamu.edu/water-striders/.