Damselflies (Zygoptera) belong to the order Odonata. Odonata means "toothed,” and refers to the chewing mandibles of these carnivorous insects. There are two suborders within Odonata: Anisoptera (dragonflies) and Zygoptera (damselflies). Suborder Zygoptera accounts for about one-third of the species in Odonata and comprises 12 recognized families and approximately 95 genera worldwide. ("Odonata (Dragonflies and Damselflies)", 2003; Corbet, 1999; McGavin, 2001; U.S. Department of Agriculture, 2002)
Damselflies are carnivorous insects that live and breed near a wide variety of freshwater habitats. They lay their eggs in water, and the immature damselflies spend the first several months or years as aquatic predators. These immature damselflies, called nymphs, have external gills that allow them to extract oxygen from the water. After undergoing metamorphosis, new adult damselflies fly away from the water for a brief period of several days to several weeks, after which they return to breed. Both adult and immature damselflies are predators whose diet consists primarily of insects. (Corbet, 1999; Silsby, 2001)
Damselflies are native to all regions of the world, with the exception of Antarctica. Tropical regions host the highest diversity of damselfly species. ("Odonata (Dragonflies and Damselflies)", 2003; Silsby, 2001; Westfall and May, 1996)
Because damselflies depend on freshwater for oviposition (egg-laying), their primary habitat requirement is the presence of freshwater. Beyond freshwater, it is not clear what factors influence habitat selection, though the structure of emergent vegetation for oviposition appears to be important. Other factors that might be important include the rate of water flow, water quality (oxygen content, pH, nutrient load), refuge from predators and variability in water level. Each species of damselfly has distinct habitat preferences for each of these variables. For example, damselflies can be found in freshwater habitats from temporary pools to waterfalls, but individual species occupy only habitats within a certain range of water speeds. (Silsby, 2001; Westfall and May, 1996)
Damselflies are long, slender-bodied insects with two pairs of membranous wings. They have broad heads with large, widely separated eyes and inconspicuous bristle-like antennae. The thorax is three-segmented, and skewed in a manner that gives the three spiny pairs of legs the appearance of being thrust forward. The legs form a basket that can be used for scooping prey out of the air. The abdomens of damselflies are very slender, ten-segmented and often brightly colored or distinctly patterned. The color of some species can change with environmental variables, fading from bright blue to dull purple in response to cool temperatures or darkness. Males of most damselfly species are more brightly colored than females. In some species females occur in more than one color phase. Frequently, in these species, one of the female color phases is similar to the coloration of the male. (Borror, et al., 1989; Silsby, 2001; Westfall and May, 1996)
Immature damselflies, called larvae or nymphs are slender-bodied with a wide head and are cryptically colored in browns and greens. One distinctive feature of damselfly larvae is the modified lower lip (labium), which is called a "mask" because it covers the underside of the head. The mask is long and hinged and armed with a set of grasping, claw-like lobes. When larvae sense prey nearby, they can thrust the mask rapidly forward and grasp prey between the lobes. Damselfly larvae also have three leaf-like gills (also known as caudal lamellae) at the tip of their abdomen, which they used to extract oxygen from the water. These gills are often strikingly patterned and can be useful for identifying nymphs. ("Odonata (Dragonflies and Damselflies)", 2003; McGavin, 2001; Silsby, 2001)
Though at first glance, damselflies appear to be very similar to dragonflies, there are several characters that distinguish the two groups. Damselflies have two pairs of wings that are similar in shape and are held closed when at rest. The rear wings of dragonflies have a much broader base than the front wings, and both pairs are held horizontally at rest. Damselflies have a broad head with eyes that are separated by more than the width of an eye, as opposed to a round head with closely placed eyes. Males have four rather than three caudal appendages at the tip of the abdomen and all females have a functional ovipositor. Damselfly larvae are slender, with three external caudal gills at the tip of the abdomen. This distinguishes them from dragonfly larvae, which have internal gills and tend to be broad-bodied. (Silsby, 2001; Westfall and May, 1996)
The smallest known damselfly is the southeast Asian species, Agriocnemis femina. This petite damselfly has a wingspan of only 20mm. The largest known species of damselfly, in the genus Mecistogaster, has a wingspan of 200 mm. ("Odonata (Dragonflies and Damselflies)", 2003; Silsby, 2001)
There are three stages in the damselfly lifecycle: egg, larva and adult. Eggs are laid in water and usually hatch after one to three weeks. The length of this period varies between and within species. Some eggs that are laid late in the summer may even overwinter before hatching. After hatching from the egg, the larval damselfly, also called a nymph, lives in water as an aquatic predator. Damselflies live for two months to three years as nymphs, undergoing 5 to 15 molts as they grow. The length of the nymphal stage varies between species and within species, and depends on temperature, food supply and photoperiodic regime. During the last larval instars, the nymph begins to develop some of the features that will prepare it for life as an adult, such as expanded eyes, flight muscles and wings. ("Odonata (Dragonflies and Damselflies)", 2003; Westfall and May, 1996)
When a damselfly nymph is nearly adult size, it crawls out of the water onto a plant stem or other substrate, and the new adult emerges from the nymphal exoskeleton. The new adult then flies away from the water, and remains away for two or more weeks. During this time, the damselfly eats voraciously (they emerge from the water with very little stored energy) while the exoskeleton hardens and develops the characteristic color and pattern of the adult and the gonads of the young insect mature. Once the adult is fully mature, it returns to an area near water to breed. In many species, this is the likely to be the same habitat where the nymph emerged from the water. Other species range more widely, and young adults may disperse to new breeding sites. (Borror, et al., 1989; Corbet, 1999; Silsby, 2001; Westfall and May, 1996)
Some species of damselflies are territorial. In these species, males defend a territory that includes high-quality oviposition sites. These males attract females and deter other males by performing aerial flight displays, which flaunt their most colorful body parts as well as their agility in flight. In non-territorial species of damselflies, males simply wait near egg oviposition sites for females to arrive. Rather than courting females, these males simply ambush them when they come within range. It is not clear why some species of damselflies are territorial and others are not. However, the differences in behavior seem to be correlated with sexual dimorphism. Species in which males are brightly colored or distinctly patterned tend to be territorial and to engage in mate guarding more so than plainly colored males. (Silsby, 2001; Westfall and May, 1996)
Sperm competition plays an important role in the mating systems of damselflies. Most of a female’s eggs are fertilized by the sperm of the last male to mate with her before she oviposits. Males, therefore, employ a few strategies to ensure their paternity. The male penis has a specialized form, and is used to displace the sperm from previous matings from the spermatheca (the sperm storage organ of the female) before releasing new sperm. Males further attempt to ensure their paternity by engaging in “mate guarding.” By guarding the female after copulation, a male can protect her from other males that may try to copulate with her remove the original male’s sperm. Males guard the female as she lays her eggs, either by flying very close to her (“non-contact guarding”) or by physically holding on to her until she has completed egg laying (“contact guarding”). (McGavin, 2001; Silsby, 2001; Westfall and May, 1996)
Some species of damselflies mate only once. Males of these species do not have a specialized penis for removing sperm. Instead, pairs copulate for periods up to several hours. This effectively excludes rival males from accessing the female until the eggs have been fertilized by the first male’s sperm. (McGavin, 2001)
Damselflies are sexually mature a few days to weeks after emergence as adults. Once sexually mature, they seek out freshwater habitat with appropriate oviposition sites. This may be the same habitat from which they emerged as nymphs, or a new location. In territorial species, males establish a territory that contains good oviposition sites and defend it from other males. In non-territorial species, males simply find habitat with good oviposition sites and wait for females to arrive. (Westfall and May, 1996)
The copulation behavior of damselflies and dragonflies is unique in the Animal Kingdom. Male damselflies have two sets of genitalia. Sperm are produced in the primary genitalia, which is located at the tip of the abdomen. The secondary genitalia, which is used for copulation, is located on the underside of the abdomen, near the thorax. Before copulation, the male damselfly must transfer sperm from the primary to the secondary genitalia by curling his abdomen into a circle. To copulate, the male damselfly uses his caudal appendages to grasp the female by the prothorax (behind the head). In this position, the male and female are said to be “in tandem.” If the female is receptive to the male, she curls her abdomen forward to join the tip of her abdomen with the male’s secondary genitalia. Sperm are then transferred from the male’s penis to the female’s spermatheca, a sac-like structure where sperm are stored until the female lays eggs. This position, in which the bodies of the male and female damselflies form a circle, is called “the wheel position.” After copulation, the female oviposits the eggs into an appropriate substrate, often while guarded by the male. ("Odonata (Dragonflies and Damselflies)", 2003; Silsby, 2001; Westfall and May, 1996)
Female damselflies have a functional ovipositor consisting of three serrated valves at the tip of their abdomen. The females use the ovipositor to make slits in plant tissue and insert one to several eggs into each slit. Unlike many species of dragonflies, all damselflies insert their eggs into a solid substrate, which can be plant material, floating wood or moss or slime. Eggs are usually inserted just below the surface of the water, but can be laid above the water in some species. In a few species, the female submerges herself by crawling down the plant stem and lays her eggs up to a foot below the water surface. After a female has laid a batch of eggs, she must wait between one and five days before mating again. During this time, the next batch of eggs matures. Male dragonflies have a constant supply of viable sperm, and therefore do not have to wait for any length of time between copulations. (Borror, et al., 1989; Silsby, 2001; Westfall and May, 1996)
There is no known parental care among damselflies. Females take care to select an oviposition site that will foster development of eggs and nymphs. However, once the eggs are laid, damselflies are not able to influence the success of their offspring.
The lifespans of damselflies vary by species. The average damselfly probably lives for three to four weeks as an adult. However, there is quite a bit of variability between and within species. Once in the adult stage, some species survive for a few weeks and some for several months. The amount of time that damselfly nymphs spend in the aquatic stage can range from weeks to years, depending on the species, temperature, food availability and photoperiodic regime. In general, tropical species spend less time in the aquatic stage and more time in the adult stage than temperate species. (Borror, et al., 1989; Silsby, 2001; Westfall and May, 1996)
Most species of damselflies (and dragonflies) require a minimum temperature in order to fly. Despite being ectothermic, they can control their body temperature to some extent by stretching out in the sun to warm up and by adjusting their orientation to the sun (tipping abdomen up) to control the amount of solar radiation they absorb. Because of this temperature limitation, most species of damselflies are diurnal. Damselflies are very agile fliers. Like the other Odonates, damselflies can control the frequency, amplitude and angle of their two sets of wings independently. Though the two pairs of wings typically beat out of phase with one another, damselflies can control them independently, and can even move all four wings at different frequencies. Despite this, damselflies do not fly with the speed and agility of their close relatives, the dragonflies. Damselflies can fly on average, about 10 km/h, whereas some species of dragonflies can fly at speeds greater than 70 km/h. (McGavin, 2001; Silsby, 2001; Westfall and May, 1996)
Damselflies are solitary creatures. Social behaviors such as swarm feeding are rare in damselflies. (Silsby, 2001)
Damselflies primarily use sight to interact with their environment and with one another. Their large eyes afford them excellent vision compared to most insects. Therefore, visual cues play an important role in communication and perception. For example, males display vivid patterns and colors on their wings, face, abdomen or legs to signal their prowess to both rival males and potential mates. Damselflies hunt visually, sighting prey from a perch before flying after them. There is evidence that damselflies can see ultraviolet light, which may provide additional visual cues that can't be seen by humans. However, the vision of damselflies is not as acute as that of dragonflies, which may account for their slower flight speed. (Silsby, 2001; Westfall and May, 1996)
Damselflies also use mechanical and chemical cues to sense and their environment. Antennal mechanoreceptors allow them to gauge flight speed and mechanoreceptors at the base of the wings gauge and control wing twisting. Also, chemical and mechanical cues are probably used in communication between mating pairs and in selection of oviposition sites. Early instars of damselfly nymphs use primarily tactile cues to detect prey and predators. As their eyes develop in later instars, vision become more important for hunting and sensing predators. (Corbet, 1999; McGavin, 2001; Westfall and May, 1996)
Damselflies are solitary, opportunistic predators. They are primarily insectivores, but will eat nearly anything that they can successfully catch and ingest. This means that they eat primarily aerial prey. Damselflies have three pairs of legs with spiny bristles that interlock to form a basket. The legs are tilted forward, so that the basket can be used to scoop prey out of the air while in flight. The short front pair of legs allow the insect to feed while flying. In general, damselflies are not active hunters. They typically hunt from a perch and ambush prey as they come into view. This strategy conserves energy and may make the dragonflies less vulnerable to predation. (McGavin, 2000; Silsby, 2001)
Adults primarily eat flying insects, such as flies, mosquitoes and moths and butterflies. They also eat beetles and caterpillars. A few species of damselflies have more specialized diets. For example, one South American species plucks spiders and/or their prey out of spiderwebs. (Silsby, 2001; Westfall and May, 1996)
Damselfly nymphs are also predators that employ a “sit and wait” strategy. They rest, hidden in vegetation, and wait for prey to come within striking distance. However, if the supply of prey is not sufficient, nymphs will take a more active approach, either moving to a new hiding place or actively swimming in search of prey. Some damselfly larvae are territorial, and defend temporary feeding sites. These larvae use their gills to perform aggressive displays to defend their territory. Damselfly nymphs will eat most moving organisms that they can catch, including fry fish, tadpoles, water beetles, and even smaller Odonate nymphs. (Gullan and Cranston, 2000; McGavin, 2001; Silsby, 2001; Westfall and May, 1996)
Damselfly nymphs are vulnerable to predation by a number of aquatic predators, including fish, water bugs, beetles and larger damselfly and dragonfly larvae. When threatened, damselfly nymphs either conceal themselves among vegetation, or swim by undulating their bodies and using their gills like a tail fin. (McGavin, 2001)
Predators of adult damselflies include fish, birds such as swallows and martins, frogs, rodents, small mammals, lizards, spiders, small bees and wasps, larger species of dragonflies and damselflies and insect eating plants such as sundew. Damselflies are agile fliers, and primarily use flight to escape predation. (Silsby, 2001; Westfall and May, 1996)
Damselflies prey on a wide variety of species. However, their effect on prey populations is thought to be small. They also serve as food for many aquatic and terrestrial predators. (McGavin, 2001; Westfall and May, 1996)
Damselfly nymphs and adults can be hosts to several species of trematodes and larval water mites. The small, reddish mite larvae attach themselves to the aquatic nymph, and then to the adult damselfly when it emerges. They feed on the damselfly’s blood for two or three weeks, and eventually leave it to return to the water where they develop into adult mites. The mites do not appear to cause significant harm to their host, though especially heavy infestations can lower the number of eggs a female is able to lay and/or eventually kill an adult. (Borror, et al., 1989; Corbet, 1999)
Damselflies are valuable indicators of environmental quality. Because they are found in a wide variety of aquatic habitats and many species have specific tolerances to environmental disturbance, population levels may be a useful measure of ecosystem health. ("Odonata (Dragonflies and Damselflies)", 2003; McGavin, 2001; Westfall and May, 1996)
There are few known adverse affects of damselflies on humans. Contrary to popular belief, adult damselflies do not bite or sting. (Corbet, 1999)
The destruction and alteration of freshwater habitats is the greatest threat to damselfly species worldwide. Without clean water and appropriate oviposition sites, damselflies are unable to breed. Causes of pollution and/or destruction of freshwater habitats include human development for agriculture, industry and housing, agricultural and industrial pollution, alteration of streamflow for irrigation, and destruction of streambanks and shoreline by livestock. Alteration of habitat through global warming may also pose a threat to damselfly populations in the future. (Silsby, 2001; Westfall and May, 1996)
Odonates (dragonflies and damselflies) are widely considered among the most ancient of insect species. Fossil evidence suggests that the order Protodonata, the forbearers of extant Odonates, appeared as early as 325 million years ago. ("Odonata (Dragonflies and Damselflies)", 2003)
Kari Kirschbaum (author), Animal Diversity Web.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
living in landscapes dominated by human agriculture.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
an animal that mainly eats meat
either directly causes, or indirectly transmits, a disease to a domestic animal
uses smells or other chemicals to communicate
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
An animal that eats mainly insects or spiders.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
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Corbet, P. 1999. Dragonflies: Behavior and Ecology of Odonata. Ithaca, New York: Cornell University Press.
Corbet, P. 1980. Biology of Odonata. Annual Review of Entomology, 25: 189-217.
Gullan, P., P. Cranston. 2000. The Insects: An Outline of Entomology, Second Edition. Malden, MA: Blackwell Science, Inc.
McGavin, G. 2001. Essential Entomology: An Order-by-Order Introduction. Oxford: Oxford University Press.
McGavin, G. 2000. Insects, spiders and other terrestrial arthropods. London: Dorling Kindersley, Inc.
Needleham, J., M. Westfall, M. May. 2000. Dragonflies of North America. Gainseville: Scientific Publishers, Inc.
O'Brien, M. 2001. "Michigan Odonata Survey Homepage" (On-line). Accessed February 05, 2004 at http://insects.ummz.lsa.umich.edu/MICHODO/mos.html.
Silsby, J. 2001. Dragonflies of the World. Washington, D.C.: Smithsonian Institution Press.
U.S. Department of Agriculture, 2002. Integrated Taxanomic Information System. Accessed February 18, 2004 at http://www.itis.usda.gov/index.html.
Westfall, M., M. May. 1996. Damselflies of North America. Gainseville, FL: Scientific Publishers, Inc.