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Tramea lacerata

By Ginger Dixon

Geographic Range

Tramea lacerata is found throughout much of Mexico and the United States as far north as Maine, northernmost Vermont, and Montana. Also called black saddlebags, this species ranges south to Baja California and Quintana Roo, Mexico, and is also found on the Hawai'ian islands, the Florida Keys, Bermuda, and Cuba. Tramea lacerata is also found in the Canadian provinces of Quebec, Ontario, and British Columbia. (Dunkle, 2000; Paulson, June 1, 1984)

Habitat

Tramea lacerata prefers stagnant or slow moving bodies of water, like those found in ditches, ponds, and small lakes. They flourish in bodies of water that lack predatory fishes. Still waters allow females to lay their eggs in characteristic "dipping" manner, without the eggs being swept away. Adults are often seen gliding in wetlands and grasslands near water. (Dunkle, 2000; Paulson, June 1, 1984)

  • Aquatic Biomes
  • lakes and ponds
  • temporary pools

Physical Description

Tramea lacerata, although fairly common, are striking insects. The hind wings are quite long and wide, with irridescent black bands on the medial parts of the wings, giving them their characteristic "saddlebags" appearance. The rest of the wing is clear. Tramea lacerata is a medium to large species of Odonata, about 5.33 cm. The body has a streamlined, teardrop shape. Males are predominately black, with deeper coloring than females. Females are larger, and have a whitish-yellow spotted pattern on the dorsal side of their abdomen. Recently emerged males appear similar to females. Females and newly emerged individuals also have lighter faces, almost yellow in color, that distinguishes them from males. Tramea lacerata has black legs in both genders. (Dunkle, 2000; Paulson, June 1, 1984)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Average length
    5.33 cm
    2.10 in

Development

Larvae are aquatic. Their gills are folded inside the abdomen to avoid harm. They take in water through their anus and pass it over their gills to breath. After internal metamorphosis occurs, with the adult body forming under the skin, an adult black saddlebags will emerge from the water and grasp a branch where it will complete the rest of its transformation. The cuticle begins to split apart due to the pressure exerted through a series of air intakes. The newly emerged adult, which is quite delicate until the new cuticle hardens, will then crawl out of its old skin (exuviae), allow the wings to open and harden, and then fly away. (Dunkle, 2000)

Reproduction

Tramea lacerata has been called "dancing glider" because of its rhythmic mating style. They mate on the branches of trees that are near water. The male will hover over the female until it is within range to grasp her head and thorax. Next, he will attach his hind quarters to the back of her head, assuming the position known as "tandem." During this phase, the male is collecting sperm from his primary copulatory apparatus, located on his ninth abdominal segment. The two will then adjust their bodies to allow the joining of their genital openings. They form a ring, which is called the "wheel position," in which fertilization occurs. Most of the 8 to 15 minutes that are spent mating is take up by the male removing the female's preexisting sperm deposit. The penis is modified for this purpose, being long enough to penetrate the females' oviduct and to remove the existing sperm. Upon completion of their first breeding, females will have enough sperm to last them a lifetime and mating is not a frequently observed event. After fertilization, the male will release the female and she will gracefully dip to the water to lay her eggs. He will continue to hover over her as she does so, and the two appear to be "dancing." When she is finished, he will grasp her again, and the process will continue. (Dunkle, 2000)

Females lay their eggs in stagnant or very slow moving waters. They will dip down to the water (exophytic reproduction) and drop the eggs into the water. Some of them migrate to the north in the spring, where they will breed. (Dunkle, 2000)

  • Breeding season
    Breeding occurs during warm weather.

Once the female lays the eggs there is no more parental involvement in the young.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

No information was found on the lifespan of black saddlebags.

Behavior

Larvae are aquatic and are aggressive carnivores. Adults may either mate in the area where they emerged or will begin to migrate. Tramea lacerata individuals migrate from August through September, but it is not certain where they go. Very little is known about migration routes and life cycles during migration. Male black saddlebags seem to be somewhat social, in that they are often observed in large feeding swarms. (Dunkle, 2000)

Communication and Perception

Dragonflies have exceptionally good vision and use it to communicate with other dragonflies, to catch their prey, and to avoid being eaten. They may also communicate with touch when mating.

Food Habits

Tramea lacerata is a member of the Libellulidae family, also known as common skippers. They use a gliding feeding style, using their long, broad hind wings to glide as they pick insect prey from the air. Tramea lacerata individuals are rarely seen perching, but occasionally will rest on the tips of branches between feeding glides. When food is ample in a particular area, feeding swarms may form. These are often made up of only males but can be mixed sex swarms as well. No feeding swarms of only females have been observed. (Dunkle, 2000)

  • Animal Foods
  • insects

Predation

Dragonflies are preyed on by aquatic predators, such as fish, when they are larvae. As adults, they may be eaten by birds such as American kestrels and common nighthawks. Their maneuverability and their exceptional sense of vision keeps them safe from most predators when they are flying adults. Larvae are usually aggressive and well-armed predators as well. They can rapidly eject water from their abdomen to shoot out of the way of predators underwater.

Ecosystem Roles

Dragonflies are important predators of insects in the ecosystems in which they live. Larvae and adults also provide food for predatory fish and for birds.

Economic Importance for Humans: Positive

Tramea lacerata is an important agent of bio-control and an indicator of ecosystem health. In both life stages of its life, black saddlebags consume a large quantity of various pest insects, such as mosquitoes. In reference to the impact the Odonata in general have on our environment, Dunkle states, "...They are one of the most visible indicators of wetland diversity and health, and their population changes allow monitoring of environmental changes" (Dunkle 2000). (Dunkle, 2000)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no negative impacts of black saddlebags for humans.

Conservation Status

Tramea lacerata is abundant and widespread. They are not currently considered species of concern in any area they live.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Ginger Dixon (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

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.

World Map

bilateral symmetry

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.

bog

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.

carnivore

an animal that mainly eats meat

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

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.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

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.

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

temperate

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).

terrestrial

Living on the ground.

tropical savanna and grassland

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.

savanna

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.

temperate grassland

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.

visual

uses sight to communicate

References

Dunkle, S. 2000. Dragonflies Through Binoculars. New York City, NY, USA: Oxford University Press.

May, M. "Dragonfly Migration" (On-line). Accessed March 12, 2001 at http://www.hsrl.rutgers.edu/BOB/migrant/may_txt.html.

Paulson, D. June 1, 1984. Odonata from the Yucatan Peninsula, Mexico. Notulae Odonatologicae, Vol.2 No.3: pp. 33-52.

Trial, L. "Pond Dragons" (On-line). Accessed March 12, 2001 at http://www.conservation.state.mo.us/conmag/2000/07/1.htm.

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