Fireflies

Lampyridae. Spanish: Luciérnagas, ciegos (General). Portuguese: Vagalumes, cagalumes, cagafogos, mamoás (Brazil). Quechua: Ayañahui (adult), pichin kuro (larva) (Peru).

For romanticists, fantasists, poets, and mythmakers, fireflies have always provided inspiration (Lenko and Papavero 1979). These unique insects are invariably afforded a beneficient position for their service in punctuating the dreaded darkness with happy light, like the stars to which they are allegorically attached:

The Pleiads, rising thro' the mellow shade,

Glitter like a swarm of fireflies tangled in a silver braid.

Tennyson, "Locksley Hall"

The Aztecs called their sonnets fireflies, tiny lights in the great darkness, little truths within the ignorance surrounding them (Nicholson 1959). In some cultures, however, they are held in suspicion or considered bad omens, for example, among the Quechua-speaking people of the Andes, who refer to them as "ghost eyes" (ananahui).

In reality, fireflies are soft-bodied, elongate beetles with well-developed luminous organs in the terminal abdominal segments (fifth segment in female, fifth and sixth in male). The white or pale green light given off is produced by a chemical change of a special type of luciferin ("firefly luciferin," a carboxylic acid) in the cells of these organs (Buck 1948). The tissues of the light organs are penetrated by numerous fine tracheae, giving them ready access to the air and allowing the insect to regulate light emission by controlling the oxygen supply (Ghiradella 1983). In the presence of air and an enzyme called luciferase, the luciferin is oxidized, and a cold light is produced (Herring 1978).

Latin American species have been little studied, but much can be extrapolated from extensive knowledge available from work in North America. The basic function of sequenced light flashed from males and females is known in some fireflies to be a reciprocal courtship signal, bringing together the sexes of the same species (Lloyd 1983). The widespread genus Photinus (fig. 9.5a) has been studied in the most detail (Lloyd 1965, Soucek and Carlson 1975). The males fly in the evening, emitting short bursts of light for precise durations and intervals. Females, perched on vegetation, perceive this display and respond with their own lights. On seeing this answer, the male turns toward the female. The pattern is repeated until the male lands near the female, finally contacting and mating with her. So irresistible is the power of these light dances that beetles may be attracted

Figure 9.5 BEETLES, (a) Firefly (Photinus sp., Lampyridae), male, (b) Railroad worm (Phrixothrix sp„ Phengodidae), larva, (c) Predatory firefly (Photuris sp., Lampyridae). (d) Firefly (Lucidota sp., Lampyridae). (e) Passalus beetle (Passalus sp., Passalidae), larva, (f) Passalus beetle, adult, (g) Chilean stag beetle (Chiasognathus granti, Lucanidae), female, (h) Chilean stag beetle, male.

Figure 9.5 BEETLES, (a) Firefly (Photinus sp., Lampyridae), male, (b) Railroad worm (Phrixothrix sp„ Phengodidae), larva, (c) Predatory firefly (Photuris sp., Lampyridae). (d) Firefly (Lucidota sp., Lampyridae). (e) Passalus beetle (Passalus sp., Passalidae), larva, (f) Passalus beetle, adult, (g) Chilean stag beetle (Chiasognathus granti, Lucanidae), female, (h) Chilean stag beetle, male.

by anyone imitating the paradigm with a flashlight.

Other kinds of the hundreds of firefly species practice similar systems. Some female Photuris (fig. 9.5c) are carnivorous, catching other species in flight (Lloyd and Wong 1983) or even going so far as to mimic the signals of Photinus females to falsely attract their males, which they capture and summarily devour (Lloyd 1965, 1984). Photuris males may even mimic these hapless Photinus males to increase their chances of finding a mate (Lloyd 1981). Additional functions for the light displays (Lloyd 1969), such as prey attraction (Lloyd 1984), and advertisement of unpalatability and illumination (Lloyd 1968), have been proposed.

Other characteristics of the adults are a broadly expanded disk-shaped prothoracic shield that totally hides the head, curved mandibles perforated by a tubular canal, and large eyes. They also possess a pungent odor and acrid-tasting body fluids, which may afford them some protection from vertebrate predators, and at least one genus, Cratomorphus, apparently is a Bates-lan mimicry model (see cockroaches, chap. 6). For Photinus, compounds called lucibu-fagins (related to the toxic steroids of certain toads) have been identified (Eisner et al. 1978). Lampyrids are host to a number of parasites and miscellaneous predators (Lloyd 1973).

The larvae are elongate, tapered, and strongly segmented, most of the segments with a flat, platelike, laterally expanded dorsum. They are predaceous like the adults and likewise luminescent. Sexually mature females of some species retain the larval body form even after maturing, still producing a bright light (larviform glowworms) to attract males.

The world fauna is composed of about 2,000 species, of which a possible 800 to 1,000 (many presently undescribed) occur in the Neotropics. Jamaica alone is home to at least 50 species (Lloyd 1969). They are principally inhabitants of moist woodlands. Dominant genera are Photuris, Photinus, and Lucidota (fig. 9.5d).

The well-known "railroad worms" of the moist forests of Paraguay, Argentina, and southeastern Brazil, so called because of their double row of yellow lights, a pair on each segment of the wingless body with a red head light, are the adult larviform females of Phrixothrix (fig. 9.5b), members of the family Phengodidae, which is related to the lampyrids (Tiemann 1970). Behavioral evidence suggests that the light organs are neurally controlled like those of fireflies (Halverson et al. 1973). They are activated when the animal is disturbed and when it is engaged in active prey capture.

References

Buck, J. B. 1948. The anatomy and physiology of the light organ in fireflies. New York Acad.

Eisner, T., D. F. Wiemer, L. W. Haynes, and J. Meinwald. 1978. Lucibufagins: Defensive steroids from the fireflies Pholinus ignitus and P. marginellus (Coleoptera: Lampyridae). Natl. Acad. Sci. Proc. 75: 905-908.

Ghiradella, H. 1983. Permeable sites in the firefly lantern tracheal system: Use of osmium tetroxide vapor as a tracer. J. Morph. 177:145-156.

Halverson, R. C., J. F. Case, J. Buck, and D. Tiemann. 1973. Control of luminescence in phengodid beetles. J. Ins. Physiol. 19: 1327-1339.

Herring, P. J., ed. 1978. Bioluminescence in action. Academic, New York.

Lenko, K., and N. Papavero. 1979. Vagalu-mes—Poeira das estrelas. In K. Lenko and N. Papavero, Insetos no folclore. Cons. Est. Artes Cien. Hum., Sâo Paulo. Pp. 379-406.

Lloyd, J. E. 1965. Aggressive mimicry in Pholuris: Firefly femmes fatales. Science 149 (3684): 653-654.

Lloyd, J. E. 1968. I llumination, another function of firefly flashes? Entomol. News. 79: 265-268.

Lloyd, J. E. 1969. Signals and systematics of Jamaican fireflies: Notes on behavior and on undescribed species (Coleoptera: Lampyridae). Entomol. News 80: 169-176.

Lloyd, J. E. 1973. Firefly parasites and predators. Coleop. Bull. 27: 91-106.

Lloyd, J. E. 1981. Mimicry in the sexual signals of fireflies. Sci. Amer. 245(1): 139-145.

Lloyd, J. E. 1983. Light in the summer darkness. In 1984 Yearbook Sci. Future, Encyclopaedia Brit., Chicago. Pp. 188-201.

Lloyd, J. E. 1984. Occurrence of aggressive mimicry in fireflies. Fla. Entomol. 67: 368— 376.

Lloyd, J. E., and S. R. Wong. 1983. Nocturnal aerial prédation of fireflies by light-seeking fireflies. Science 22: 634-635.

Nicholson, I. 1959. Firefly in the night: A study of ancient Mexican poetry and symbolism. Faber and Faber, London.

Soucek, B., and A. D. Carlson. 1975. Flash pattern recognition in fireflies. J. Theor. Biol. 55: 339-352.

Tiemann, D. L. 1970. Nature's toy train, the railroad worm. Natl. Geogr. 138: 56-67.

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