Boreal bluets (Enallagma boreale) are a species of damselfly native to the Nearctic region. They are common in northern North America, ranging from coast to coast in Canada and the United States. In Canada, they are widespread in the subarctic, from Nova Scotia to British Columbia, and north into the Yukon and the western mountains. In the United States, they can be found from New England to California, and range as far south as Virginia in the east, and Arizona and New Mexico in the west. (Duffy and Liston, 1985; Westfall Jr. and May, 1996)
Their larvae are aquatic, and can be found in lentic habitats, typically slow streams, ponds, small lakes, and semi-permanent ponds. Boreal bluets are a freshwater species, though they can tolerate both saline and alkaline conditions. Adults are terrestrial, and typically can be found near the bodies of water from which they emerged. These bodies of water are located in woodlands, peatland bogs, marshes, and in the mountains. (Beirinckx, et al., 2006; Duffy and Liston, 1985; Glotzhober and McShaffrey, 2002; Paulson, 2011; Rivard, et al., 1975; Scultz, 2009; Westfall Jr. and May, 1996)
Adult boreal bluets are 28 to 36.6 mm in length, with a hind wingspan of 17 to 22 mm. Due to their ovaries, females tend to weigh more, at about 46.0 mg, while males weigh about 32.6 mg. Their coloration is primarily blue and black. Males have a blue face, while the back of their head is pale blue or yellowish. Their pronotum is black, and their thorax is blue and fades to cream. Their legs are blue or tan with black stripes. The dorsal side of their abdomen is bright blue, with pale blue or yellow on their lateral sides, and black markings and stripes. There are 3 short dark bands, followed by 2 long dark bands on their abdomen. Their cerci are black and apically rounded in profile. Females can be distinguished by the lack of pits on their pronotum. They are also polymorphic, with two morphs. One female morph shares a close resemblance to males in coloration and markings, while the other is tan, yellowish-green, or pale blue. Their head and thorax are similar to males, though their femora have fewer black markings. Their abdomen is mostly dark, with significant light areas on segments 8, 9 and 10. During the teneral stage, their wings have a rainbow sheen, and their body is soft and grey or brown in color. Sexually mature adults have brightly colored, firm bodies and clear wings. Larvae are aquatic, and have a long, thin body with gills on the posterior end. They are usually greenish or brown. Larvae have a large labium that can extend to catch prey. The labium is long and hinged, so it rests beneath the head and covers the mouthparts at rest. Final instar larvae can be distinguished by their prominent wing pads. Their gills are usually pale, and much longer than they are broad. Their eyes are rather large, and their abdomen is covered in setae. It can be difficult to identify individual Enallagma species, as many bluets must be distinguished microscopically. Boreal bluets are especially similar to northern bluets (Enallagma cyathigerum) though they are not found in the same area. Males of Enallagma species have unique terminal appendages, while females have unique mesostigmal plates, located behind and underneath the prothorax. (Acorn, 2004; Anholt, et al., 1991; Forbes, 1991; Glotzhober and McShaffrey, 2002; Hecker, et al., 2002; Walker, 1944; Westfall Jr. and May, 1996)
Boreal bluets are hemimetabolous. Adults typically emerge in the summer, when they mate and oviposit eggs in bodies of water, then die shortly after. Egg hatching time is water temperature dependent, taking as few as 11 days at 27.5° C to 61 days at 17.5° C. Typically, eggs laid in June hatch in July. There are 5 or 6 larval instars, larvae reach the later instars by October. As temperatures drop and winter approaches, the larvae overwinter. Larvae are able to withstand water temperatures as low as -4° C. They resume activity in mid-April, and molt and emerge from the water as a teneral, a sexually-immature adult. This stage lasts 4 days to several weeks, during which, tenerals fly and feeds constantly. Female tenerals take longer to develop since they have more mass to support in the developing ovaries. Typically one generation is produced each year, but some populations are semivoltine, and larvae overwinter twice. This is likely in colder regions, where larvae resume activity later in the season due to cold water temperatures and cannot complete development in time. (Acorn, 2004; Baker and Clifford, 1982; Beirinckx, et al., 2006; Duffy and Liston, 1985; McPeek and Peckarsky, 1998; Rivard, et al., 1975; Scultz, 2009)
For boreal bluets, mating occurs during the summer, typically June to July, though in warmer regions it can begin as early as May and end as late as September. Males spend much of their time near the breeding site, at the margin of lakes or ponds, while females forage farther away while they mature batches of oocytes. When females are receptive, they return to the breeding site. Males grasp the females by the mesostigmal plate with their terminal appendages, and fly in tandem. The terminal appendages and mesostigmal plate of each species has unique characteristics, which prevents crossbreeding, as they would not be able to connect and fly in tandem. In males, the genital opening and copulatory organs are separated in the abdomen. The male must transfer his sperm from the end of the abdomen to the seminal vesicle under the second abdominal segment. The female's abdomen must swing forward, with the end making contact with the second segment, where sperm transfer takes place. This is called the "wheel" position. Copulation lasts 23 minutes on average; males usually perch on vegetation and grasp the females. Boreal bluets are polygynandrous, both males and females mate multiple times with different mates, though they likely mate no more than once a day. There has much discussion about the role of female coloration in mating. Pale tan or green females are easily identified, while blue females have been referred to as male mimics. One theory suggests by mimicking males, they avoid harassment from potential male mates. However, this would likely be detrimental to their reproductive success, as males would not select them as mates. This does not seem to be the case, though, as males do mate with them, so they probably should not be considered mimics at all. It is uncertain what purpose the male-similar coloration serves. (Beirinckx, et al., 2006; Forbes, 1991; Glotzhober and McShaffrey, 2002; Miller and Fincke, 1999; Paulson, 2011; Rivard, et al., 1975)
Oviposition usually occurs while the male and female are still flying in tandem, though sometimes females oviposit alone. After mating, the pair spends several minutes searching for an oviposition site, and then up to an hour laying eggs on the surface or underwater, eggs are typically laid on leaves or plant stems. Each female has clutches of almost 400 eggs. Females lay multiple batches, requiring time between each mating to mature their oocytes. While doing so, females leave the breeding site and go to areas farther from water where males are less abundant. (Anholt, 1994; Glotzhober and McShaffrey, 2002; Rivard, et al., 1975)
Boreal bluets provide provisioning in the eggs, and lay them in a suitable aquatic habitat. Otherwise, adults provide no parental care. (Rivard, et al., 1975)
Development from egg to adulthood can take several months to almost two years in some populations. Adults live 4 days on average, though they can live as long as 17 days. (Paulson, 2011)
Adult flight and foraging activities tend to be severely impacted by strong winds and rain. With large wings and small bodies, these weather conditions can cause difficulties. If bad weather is approaching, boreal bluets abandon their pond or lake and take cover in vegetation. They can likely detect the drop in temperature and the decrease in light intensity, though this may just mimic nightfall, so they return to their night roosts. They are diurnal, spending the night in vegetation. Males and females forage differently. Females spend more time away from the body of water where they emerged, to avoid unwanted male attention while they mature a new batch of oocytes. They need more energy to develop oocytes, so they spend more time foraging. Males spend less time foraging, as they require less energy, and stay closer to the water. Males are non-territorial, and adults are solitary except when mating. Larvae are sit and wait predators, and are largely solitary. In some species, larvae can be very territorial, but this does not appear to be true for boreal bluets. When necessary, they can use their gills to swim. (Anholt, et al., 1991; Coughlan, et al., 1985; Westfall Jr. and May, 1996)
Adults stay near the ponds and lakes where they emerge, though females are more likely to disperse farther than males. (Beirinckx, et al., 2006)
Vision is important for damselflies. The intensity of sunlight can be used as a behavioral cue; if sunlight decreases, nightfall or a storm may be approaching, signaling to adult damselflies that they should take cover in vegetation. They also use their sight to hunt prey, and likely have very good depth perception, as their eyes are spaced widely apart. Color markings and patterns are used as visual cues to identify potential mates. Tactile cues are also used during mating, as the male grasps the female with his terminal appendages to fly together. If their parts do not fit together, if perhaps a male tries to mate with a similar looking yet different bluet species, then the pair will not be able to mate. Adults have mechanoreceptors at the base of the wings, used during flight. Larvae primarily use their antennae to find prey by feeling it as it moves nearby. Later instars also use sight to hunt. (Paulson, 2011; Westfall Jr. and May, 1996)
Adults are insect predators. Much of their prey are airborne, such as small flies, mayflies, and smaller dragonflies and damselflies. They can also pluck insects such as aphids off of plants. Larvae are also predatory, and sit and wait for prey to swim by, before shooting out their lower lip and snatching the prey. They feed on zooplankton (Daphnia), as well as other aquatic insects and organisms, including other Odonata larvae. (Coughlan, et al., 1985; Duffy and Liston, 1985; Paulson, 2011)
On the rare occasion that boreal bluets are found in fish-inhabited waters, the larvae are heavily preyed upon by freshwater fish of family Centrarchidae. However, boreal bluets are almost always found in fish-less habitats. Not only does this eliminate the threat to the larvae, but it also eliminates the threat of fish preying on adults ovipositing in the water. In fish-less riparian habitats, dragonflies are typically the top predator, and both adults and larvae prey on both life stages of boreal bluets. Adult boreal bluets are also preyed upon by birds, spiders, robber flies, and even other damselflies. To defend themselves, adults often perch on plant stems, aligning their bodies with the stem. By staying on the opposite side of the stem, they hide fairly well from predators. Larvae are preyed upon by frogs and aquatic insects. Their green or brown coloration serves as camouflage. Cannibalism is also a threat, as larger larvae prey on smaller larvae and eggs. (McGuffin, et al., 2006; McPeek and Peckarsky, 1998; Paulson, 2011; Westfall Jr. and May, 1996; Wisenden, et al., 1997)
Boreal bluets prey on many insects, and also serve as prey to other insect species, as well as vertebrates like birds and frogs. Boreal bluets are second intermediate hosts for frog lung flukes (Haematoloechus longiplexus) and can also host parasitic gregarines (Apicomplexa: Eugregarinidae), which can live in their midgut, though their effects on the host seem minimal. Boreal bluets have overlapping ranges with many other bluet species. Interestingly, boreal bluets are never found in the same area as northern bluets despite being virtually identical in appearance, and having very similar ecology. No one knows why they separate when they are so similar. (Acorn, 2004; Hecker, et al., 2002; Novak and Goater, 2013; Paulson, 2011)
There are no known positive effects of boreal bluets on humans.
There are no known adverse effects of boreal bluets on humans.
Boreal bluets have no special conservation status.
Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
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.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
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
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
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.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
An animal that eats mainly insects or spiders.
fertilization takes place within the female's body
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.
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.
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
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
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.
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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