Ecological and Biological Studies on the West African Firefly Luciola discicollis (Coleoptera: Lampyridae)

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Abstract
Luciola discicollis Castelnau is normally found in moist grasslands near or away from bodies of water. Light intensity, height and density of vegetation, and soil conditions are important factors in determining its habitat. The optimum temperature for larval flashing activity is between 19°–26°C, with the relative humidity 90% or higher; the duration of a flash depends upon the temperature and relative humidity at the ground surface. In comparison with adults, the larvae are less affected by light intensity or weather conditions as their activity is restricted to the ground surface with grass coverage. Imaginal populations consist of approximately equal numbers of both sexes, although males are easier to find than females. Adult females were found to migrate for several hundred meters, flying 2.5–12.0 m above the ground at a speed of 2–5 km per hour, and landing in different areas where the males of the same species signal by flaring. The function of migration evidently is distribution of eggs into wider areas, since most of the females migrated either before or during oviposition. In this connection, the females were shown to possess relatively longer wings than the males. Up to 50 eggs per female are laid on the moist soil; the incubation period averages 9 days. Development of the larvae takes approximately 5 months, during which the animals grow from 1.5 to 12.0 mm long. The larvae, which undergo approximately 5 molts, are luminous in all stages. The last-instar larvae construct earthern pupal cells in which prepupal, pupal, and preimaginal periods are spent, covering an average period of 8 days. The larval light organs function throughout the prepupal and pupal periods, at the end of which adult light organs become recognizable. The preimago is characterized by both larval and imaginal light organs functioning simultaneously ; the former disappear upon emergence of the adult from the pupal cell. Adults mate immediately and live about a week. The mating flight of males occurs from immediately after sundown until about 8 PM. No definite exchange of flashings between sexes was observed in this species, but there is no doubt that the adult light organs function in bringing the sexes together. Several low, short-distance flights by females are essential for oviposition. Adults normally take no solid food. Testes become enveloped in a common fat sac at the end of the pupal period; this sac, however, disintegrates toward senility. In females, eggs begin to develop during the preimaginal period and the first oviposition takes place 3–4 days after emergence, with the second following normally 3 days after the first. Oviposition occurs throughout the year. Females die soon after the second egg laying.

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