Lampyris noctilucacommon glow-worm

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Geographic Range

In Great Britain, Lampyris noctiluca favors chalky or limestone areas. It has been found in valleys in Wales and Scotland. (Scagell 1994) The species occurs elsewhere in Europe, for example in Belgium and Finland.

Habitat

They need an open area where the females can display to attract a male in June, July, and August. They retire into the ground during the day. They prefer open grass or hedges to woodland, but rarely are they to be found on land which has been improved for agriculture. (Anonymous 1995)

Physical Description

The glow worm, Lampyris noctiluca, is actually a beetle in the insect family Lampyridae meaning "shining ones" in Greek. This family also includes other glowing species. Although Lampyris noctiluca is often referred to as a glow worm, it isn't worm-like at all. Other names that you may have heard for the Lampyridae family in general are fireflies and lightning bugs. Lampyris noctiluca is usually brownish to blackish in color. The adult female is 12-20 mm long, while the males are much smaller. The larvae are often only a few milimeters long. (Borror & White 1970; Scagell 1994; Tweit 1999)

The males possess two pairs of wings, but use only the second pair for flying. The first pair of wings, the elytra, form a cover over the second pair. The females do not fly. (World Book 1998)

They are soft-bodied and elongated. Their head is concealed from above by a pronotum, and their antennae are threadlike. Only the last few abdominal segments are luminous. (Borror & White 1970)

The adult female is the one responsible for the most active glowing although the larva, which is very similar to the female in respects, also glows. The male may glow slightly but is very different from the female who uses her glowing organs to attract and stimulate the male. Larvae glow much more faintly, and only intermittently, for a few seconds at a time. They are also not worm-like but have segmented bodies and six legs at the head end, quite similar to adults. However, when they help themselves along with their tails, they do appear a bit like caterpillars. (Alliston 1998; Scagell 1994)

Reproduction

To attract the males who are flying at about a meter high, the female finds a plant stalk to climb. When she is clear of most of the vegetation on the ground she bends her abdomen upwards displaying her glowing organs in hope of attracting a passing male. (Alliston 1998)

Each individual female has an adult glowing life of a few weeks until she mates, since she dies soon after laying her eggs. After a few weeks the eggs hatch into larvae, and they remain as larvae for one or two summers, feeding on small snails which they apparently paralyse before sucking them empty. The two or even three-year gap between a mating and the subsequent appearance of an adult helps to explain the characteristic "boom or bust" cycles of glow-worm populations. It's possible to find plenty on a site one year, yet few or none at all the next. (Scagell 1994)

Lampyris noctiluca is the only known example of hormonal influence on sex determination in insects. Sexual differentiation of male and female gonads begins during the fourth larval instar. The differences are subtle at this stage. Male cells in the apical tissue begin to divide during this time, whereas in females it is cells in the basal tissue of the gonads that would divide. When testes were transplanted into females earlier than the fifth instar larvae, they induced a transformation, or a masculinization, in the female recipients. Testes could not produce such effects in female-determinted larvae after late in the fifth instar. Converse experiments did not produce feminization in young males. Hence, ovaries of this species can not feminize males, but testes can transform ovaries of pre-fifth instar females into testes. (Stanley 1997)

Behavior

Lampyris noctiluca adults are active at night and spend their days in moist places under debris. The larvae are also nocturnal and are rarely seen, however, whenever conditions are right for snails, usually between the months of April and October, they can be spotted. The adult stage, while short, is the easiest to spot. They glow for a few hours at a time, and usually stop glowing soon after mating. The best time to see the insect is between 10 pm and midnight on dry summer nights (rain tends to make the females shelter lower to the ground and in thicker vegetation). (Glow Worm Lampyris noctiluca 1993; Scagell 1994)

Food Habits

Adults rarely feed. Despite their diminutive size, the larvae are the fierce predators. They roam leaf litter in search of tiny snails and slugs, which they bite and inject with a neurotoxin that both immobilizes and liquefies its meal. They then suck their prey empty. (Tweit 1999)

Economic Importance for Humans: Positive

Dr. Robert Ledley developed a test that can determine within minutes the best treatment for a TB patient. This new test was developed by using the same substance that makes fireflies glow. TB bacteria are injected with a gene that produces luciferase, the same enzyme that helps to illumine fireflies. As long as the bacterium is alive it keeps lighting up, but when it dies the luciferase gene becomes inactive and the light goes out. Therefore, it can be distinguished within minutes which antibiotics douse the TB bacteria's lights and thus will work best against that strain of TB. Previously it took as much as 10 weeks to figure out which strain had infected a patient. (Riordan 1999)

Conservation Status

Outdoor lighting may threaten the species survival. Artificial night lighting-from street lights to headlights-may distract fireflies cruising for mates, drowning the insects' signals in excess light. Lamp-free reserves such as sheltered hollows shielded from lighting has been suggested to save Lampyris noctiluca. (Frank 1996; Tweit 1999)

The survival of fireflies depends on the existence of the natural areas in which they breed and live. Populations are declining because of destruction of habitat, especially wetlands. Researchers also speculate that commercial firefly collection for luciferase is also a factor in the decline. (Anonymous 1995; Tweit 1999)

Other Comments

The light of a firefly is actually cold light, producing very little wasted heat. Unlike an ordinary incandescent lightbulb, for instace, which transforms only about 3 percent of electrical energy into light (losing the other 97 percent as heat), firefly light is 90 to 98 percent efficient. Their light is produced through a chemical reaction that involves three compounds: a small organic molecule called luciferin (named for the fallen archangel, Lucifer, the bearer of light); adenosine triphosphate (ATP), a molecule that drives the synthesis of protein; and the catalyst luciferase. When luciferase is added to luciferin and ATP in the presence of oxygen, the energy of ATP causes the luciferin to glow. (Tweit 1999)

The bioluminescent advertisement seems counterproductive, destined to draw predators such as frogs and birds. New research, however, shows that most fireflies in every life stage contain potent steroids. So powerful are these poisons that when thrushes are fed insects painted with an inconspicuos firefly extract, they promptly vomit up their meals. The glow is indeed an advertisement, but like the orange color of a monarch butterfly, the light says "I'm poisonous!" rather than "Eat me!" (Tweit 1999)

Dr. Douglas W. Tallamy, an entomologist at the University of Delaware, offered mice fireflies and mealworms. All the mice rejected the foul-tasting fireflies in favor of the mealworms. In addition, the researchers showed that mice had the ability to associate light with bad tasting tidbits. Dr. Tallamy and his colleagues concluded that predators equate the firefly larvae's luminescence with its bitter taste. This study is believed to have been the first laboratory-based evidence of an insect using bioluminescence to advertise to predators that it is an untasty meal. (Hsu 1997)

Contributors

Melissa Gayton (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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.

ectothermic

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

native range

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

References

1998. The 1998 World Book Encyclopedia, International Edition. World Book, Inc..

1993. "Glow Worm Lampyris noctiluca" (On-line). Accessed February 19, 2000 at http://www.bracknell-forest.gov.uk/council/departments/leisure/countryside/bap/glow_worm.htm.

Alliston, Mark, July 22, 1998. "Glow Worm Lampyris noctiluca" (On-line). Accessed February 19, 2000 at http://www.the-timeless-dimension.com/in008.htm.

Anonymous, Mar 1995. Fireflies/Lightining Bugs(Lampyridae). Organic Gardening, 42(3): 24.

Borror, Donald J., W. 1970. Peterson Field Guides: Insects. Boston: Houghton Mifflin Company.

Frank, Kenneth D., July 1996. "Impact of Outdoor Lighting on Moths" (On-line). Accessed February 19, 2000 at http://www.darksky.org/ida/ida_2/info109.html.

Hsu, Karen, July 8, 1997. Survival of Baby Fireflies. New York Times: C5.

Riordan, Teresa, Aug 30, 1999. Researchers marshal more effective weapons in the battle to contain a tuberculosis resurgence. New York Times: C9.

Scagell, Robin, 2004. "Glow Worm - Lampyris noctiluca" (On-line). Accessed October 11, 2004 at http://www.deepblue.uk.net/uknature/pages/glowworm.html.

Stanley, David, 1997. "Entomology 401/801-- Insect Physiology: Home Page" (On-line). Accessed February 19, 2000 at http://ianrwww.unl.edu/ianr/entomol/ent801/repro.html.

Tweit, Susan J., July/Aug 1999. Dance of the Fireflies. Audubon, 101(4): 26-31.