Headlight Beetles

Elateridae, Pyrophorini, Pyrophorus. Spanish: Cocujos (General), carbunclos (Costa Rica), cucubanos (Puerto Rico). Portuguese: Pirilampos (Brazil). Flying candles, fire beetles, peeny wallys.

Headlight beetles are large click beetles, notable in their unique ability among click beetles to produce light. An intense glow emanates from two round luminescent organs on the prothorax (the "headlights") and a broad area on the underside of the first abdominal segment. In flight, both sexes produce a brilliant blue-green streak of light that dazzles the onlooker.

The original genus has been broken up so that the hundred or so species originally placed in Pyrophorus are now distributed among 17 genera; only 26 species remain in the genus Pyrophorus (Costa 1976). They all occur in forests from southern Mexico to southeastern Brazil (40° S) and the West Indies.

The brightness and constancy of their light is legendary (Perkins 1869). Peter Martyr's History of the West Indies (1516) notes a number of uses to which these beetles were put in the sixteenth century: the Islanders ... go with their good will by night with 2 Cucuji tyed to the great toes of their feete: for the travailer goeth better by direction of the light of the Cucuji, then if he brought so many candles with him." Humboldt noted that a dozen of these beetles placed in a perforated gourd sufficed as a reading lamp (Allen and Wooton 1963). In 1535, Oviedo noted, "The Indians in fun stained their hands and faces with a paste made from those 'cocuyos' to scare others not familiar with the ruse." It is said that Sir Thomas Cavendish on his celebrated voyage to the West Indies in 1634, desisted on his first landing, seeing the light of Pyrophorus on shore and thinking they were Spanish soldiers. Guenther (1931: 228) adds further anecdotes: "Wasmann facetiously suggested that it might one day be possible to prepare pills of 'cucujin,' which scholars might swallow in order to be able to work by the light of their own bodies. I have been told that burglars have sometimes rubbed their faces with the green luminous substance, in order to frighten the inmates of the house they were entering."

Martyr started the widespread myth that these beetles catch mosquitoes and were useful in keeping houses free of these pests. In reality, the adults are phytophagous, feeding on rotting fruit and plant exudates.

Adults are attracted to artificial light, a flashlight, or a glowing cigarette. In the early days of Hispaniola, the natives collected them by going out at night with a burning coal (Martyr 1516).

Headlight beetles are fairly large (BL 2— 4 cm), typically elaterid in form, that is, elongate, the prothorax with toothed rear angles (fig. 9.4f). All are uniformly dark brown, except for the two prothoracic spots, and have serrate antennae.

Mature larvae and pupae also luminesce. The former display bright round spots laterally and transverse zones on the dorsal and ventral plates of all segments except the prothorax, which glows on the margins of its dorsal plate. The larvae (Casari-Chen 1986) are predaceaous soil dwellers, feeding on scarab and other beetle larvae (Costa 1970).

References

Allen, I. M., and A. Wootton. 1963. Man's use of fire-flies for light. Entomol. Mon. Mag. 99: 27-30.

Casari-Chen, S. A. 1986. Larvas de Coleóptera da regiäo Neotropical. XV. Revisäo de Pyrophorini (Elateridae, Pyrophorinae). Rev. Brasil. Entomol. 30: 323-357.

Costa, C. 1970. Genus Pyrophorus. 3. Life history, larva and pupa of Pyrophorus puncta-tissimus, Blanchard (Col., Elateridae). Mus. Zool., Univ. Säo Paulo, Pap. Avul. Zool. 23: 69-76.

Costa, C. 1976. Speciation and geographical patterns in Pyrophorus Billberg, 1820 (Coleóptera, Elateridae, Pyrophorini). Mus. Zool., Univ. Säo Paulo, Pap. Avul. Zool. 29: 141-154.

Guenther, K. 1931. A naturalist in Brazil. Allen & Unwin, London.

Martyr, P. 1516. [1912], Decades (Alcala de Henares). Trans, by F. A. MacNutt as De Orbe novo: The eight decades of Peter Martyr d'Anghera. 2: 310-313. Putnam's Sons, New York.

Perkins, G. A. 1869. The cucuyo; or, West Indian fire beetle. Amer. Nat. 2: 422-433.

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