Bioluminescence and Biological Aspects of Brazilian Railroad-Worms (Coleoptera: Phengodidae)

Abstract

Seventeen Brazilian railroad-worm species in 8 genera (Phrixothrix, Stenophrixothrix, Mastinocerus, Mastinomorphus, Taximastinocerus, Brasilocerus, Euryopa, Pseudophengodes) collected in southeastern and west central Brazil, near the Parque Nacional das Emas, were studied. The studied species generally inhabit pluvial tropical forests, but Mastinomorphus sp., was found in open marshy areas of west central cerrados. The life history of Brazilian phengodids resembles in many aspects that of the North American Zarhipis integripennis (LeConte). We detail here the life cycle of Mastinomorphus sp.1 In larvae and in larviform females of the species studied, the bioluminescence ranges from yellow-green to red (λmax = 562-638 nm) for the head and from green to orange (λmax = 535-592 nm) for the lateral lanterns. In adult males, the emission color varies from green to yellow (λmax = 549-580 nm), except Euryopa spp., who emit orange light (λmax = 592-598 nm). Luminescence was observed among all life stages of the species studied, in contrast to the North American Phengodini, whose adult males do not glow. Bioluminescence from the larval and female head lanterns may serve for illumination of the nearby environment, whereas the lateral lanterns of larvae and adult males and females seem to be important for self defense.