Phosphaenus hemipterus (Geoffroy, 1762)
The larva feeds on earthworms. The species occurs in many countries: Portugal, Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Italy, Latvia, Lichtenstein, Lithuania, Luxembourg, Netherlands, Poland, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, and Switzerland. It exists also on North America and Canada. It has also been spotted regularly in the Parque Biológico de Gaia.
Behaviour and where to observe
The larvae can be found under rocks, logs and leaf litter. The adult males are exceptional. First of all they are diurnal and are thus especially active during the day. On warm and sultry days, they can be seen wandering along roads, stone pavements, walls and other passageways. This is the only species where also males are flightless: they are brachypterous – with shortened wings and elytra.
Adult female: Likes to hide under leaf litter, logs or rocks. They resemble mini Lampyris females. The light it emits consists of two spots of green light. Like the males, she only glows when disturbed.
Adult male: Completely black (sometimes dorsally pale spots on penultimate segment where light organs are situated), has two long antennae and two light spots on its back, inherited from the larval stage, which he turns on when feeling threatened. Being shortwinged he cannot fly and can be found crawling on the ground. It is the only species where the males’ wings and elytra are undevelopped and where males, just like the females, cannot fly.
Size
Larva: 3 to 13 mm. Adult male: ca. 7 to 10 mm. Adult female: ca. 10 to 12 mm.
Trivia
Because the main goal of the adult firefly, as an individual, is to reproduce, an encounter between both sexes in this diurnal species happens through chemical communication, by the use of olfactory signals (pheromones), contrary to the light signals and visual communication used in the nocturnal species. This explains why the males have such large antennae: in insects the antennae function like noses.
Text and photos - «Fireflies and Glow-worms of Portugal», 2015, ISBN n.º 978-989-98330-9-8.
