''Gerris lacustris'', commonly known as the common pond skater or common water strider, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

water strider The Gerridae are a family of insects in the order Hemiptera, commonly known as water striders, water skeeters, water scooters, water bugs, pond skaters, water skippers, water gliders, water skimmers or puddle flies. They are true bugs of the ...

, found across

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Description

Water striders vary in length ranging between and in size. Their body shape is very slender and elongated. They have six

legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element cap ...

; the first pair is short and stubby while the other two pairs are thin and elongated which are used for moving over the water surface which we call "walking on water". The first pair of legs is used for holding its prey, the middle pair propels the bug along the surface of the water with either a

rowing Rowing is the act of propelling a human-powered watercraft using the sweeping motions of oars to displace water and generate reactional propulsion. Rowing is functionally similar to paddling, but rowing requires oars to be mechanically a ...

or jumping motion, and the hind pair of legs is used as

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...

s. The entire body of ''G. lacustris'' including its legs is covered with many tiny hairs that have a wax-like coating. ''G. lacustris'' are dark brown in colour. Water striders have very strong sucking mouthparts known as a

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

or beak.

Reproduction

''G. lacustris'' females are usually significantly larger than the males and the

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

production rate is limited by the amount of food resources that are available to the female; the more food there is the more eggs the female lays. The adult water striders emerge around April and May. It is around this time that females lay eggs where the eggs undergo a process that takes about 12 to 14 days to develop before they are able to hatch. Hatching doesn't necessarily follow the eggs when their development is complete; hatching heavily depends on the

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

that the egg is exposed to in its environment. After hatching, ''G. lacustris'' go through another separate development process known as

incomplete metamorphosis Hemimetabolism or hemimetaboly, also called partial metamorphosis and paurometabolism,McGavin, George C. ''Essential Entomology: An Order-by-Order Introduction''. Oxford: Oxford University Press, 2001. pp. 20. is the mode of development of certain ...

. In this process, the

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e or

nymphs A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

progress through a series of moults which basically are stages known as

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

s. There are five instars in the developmental process, with each one progressively longer than the last. The incomplete metamorphosis process usually lasts about 24 to 30 days for larvae to become an adult. ''G. lacutris'' males prolong their mating in the presence of other males because they are guarding their female against harassment from the other males. It was found that males influence the duration of

copulation Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...

while the females influence the copulation frequency.

Food and nutrients

''G. lacustris'' is a

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

y insect. The species hunts on or below water surface for insects and other small invertebrates using their strong forelegs which end with claws. They also have piercing and sucking mouthparts in order to consume other small insects that fall into the water surface and to feed on live and dead insects such as

culiseta annulata ''Culiseta annulata'' is a species of mosquito in the family Culicidae. It is found in the Palearctic. Ecology ''Culiseta annulata'' overwinters in its adult stage. In Northern Europe, females of this species are found in caves from autumn to e ...

, non-biting midge, and other water invertebrates. With their front pair of legs they’re able to detect ripples and sense vibrations in the surface film from struggling insects and handle or grasp their prey. ''G. lacustris'' eat other small invertebrates and digest them internally.

Adaptations

Water striders have the ability to move quickly on the water surface and have

hydrophobic In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thu ...

legs. On average, a water strider can move 1.5

metre per second The metre per second is the unit of both speed (a scalar (physics), scalar quantity) and velocity (a Vector (mathematics and physics), vector quantity, which has direction and magnitude) in the International System of Units (SI), equal to the sp ...

by paddling forward with the middle pair of legs while the forelegs and hind legs act as a rudder. Waters striders also have the ability to stand effortlessly on water due to their non-wetting legs. Because they have tiny hairs with nanogrooves that cover their bodies, they have a water resistance effect. Water striders rely on

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension (physics), tension is what allows objects with a higher density than water such as razor blades and insects (e.g. Ge ...

to walk on top of water. Through evolution, water striders have developed a unique arrangement of legs which gives them the gliding ability with greatly elongated med-legs. The

Hox gene Hox genes, a subset of homeobox, homeobox genes, are a gene cluster, group of related genes that Evolutionary developmental biology, specify regions of the body plan of an embryo along the craniocaudal axis, head-tail axis of animals. Hox protein ...

ultrabithorax Ultrabithorax (Ubx) is a homeobox gene found in insects, and is used in the regulation of patterning in morphogenesis. There are many possible products of this gene, which function as transcription factor, transcription factors. Ubx is used in t ...

" lengthens legs in insects. If its pool should dry out during a

drought A drought is a period of drier-than-normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, ...

, a water strider will travel overland to find wetter pastures to settle in. The front pair of legs of a water strider do not act as a rudder - they are very short and are held up in the air, ready to grab prey. They also do not feel the vibrations in the water of prey—the middle and hind pair of legs do this.

References

{{Taxonbar, from=Q20863 Gerrini Hemiptera of Europe Insects described in 1758 Taxa named by Carl Linnaeus