Lights Ahead: Morphology and Life Stages of the Spotted Tortoise Firefly, Aspisoma sticticum Gemminger, 1870 – Fireflies with a Unique Extra Pair of Lanterns on the Larval Pronotum (Coleoptera: Lampyridae)

Abstract

Fireflies (Coleoptera: Lampyridae) spend most of their lives as larvae. Nevertheless, immature stages of over 99% of species remain unknown, which gives an incomplete picture of the species' biology. Moreover, fireflies are most diverse in Central and South America, where most species remain known from the centuries-old taxonomic descriptions based on male morphology. Here, we redescribe the spotted tortoise firefly, Aspisoma stictucum Gemminger, 1870 based on immature and adult stages, provide illustration of diagnostic features and an updated distribution map. A definitive diagnosis of adult A. sticticum among congeneric species remains elusive due to lack of comparative studies, but the following combination of traits allow for discrimination of co-occurring species: size large (2–4 cm); pronotum and elytron testaceous with variable developed black spots, pronotum subtriangular; elytron widest at basal third. A. sticticum larvae is unique among fireflies in having paired pronotal lantern spots, in addition to the typical abdominal lantern spots. In fact, these sets of larval lanterns have independent control, as observed in the field and in the lab. Noteworthy, the pronotal lanterns cannot be seen in dead specimens, which stresses the need for field studies towards a deeper and more comprehensive understanding of fireflies.