Antennomere numbers in fireflies (Coleoptera: Lampyridae): unique patterns and tentative explanations

Why the Long "Horns"? Fine-Scale Morphology Suggests Tactile Demands Contributed to the Exaggeration of Male Longhorned Beetle Antennae (Coleoptera: Cerambycidae)

Insect antennae are covered in hairlike sensilla that detect diverse environmental cues. Selection on these functions has produced a bewildering variety of antennal forms, including many examples of sexual dimorphism (SD). Antenna length SD is particularly common, but poorly understood, in longhorned beetles (Coleoptera: Cerambycidae). Extremely elongate male antennae may extend the reach of individuals searching for mates, enabling rapid recognition via antennal contact. Alternatively, they may increase sensitivity to airborne pheromones by bearing more olfactory sensilla. We tested these hypotheses by modeling sensillum distributions and abundances across species and sexes of Anoplistes, a cerambycid genus with extensive variation in antenna length and SD. We found limited evidence that olfactory sensillum abundance scales with antenna segment length; instead, mechano- and contact chemosensory sensilla cluster near the antenna tip, consistent with contact-mediated mate recognition. If the tip segment serves an important tactile role, that may explain why it is exceptionally elongated in males of several species with long, sexually dimorphic antennae. In other Anoplistes species with strong antennal SD, however, all segments exhibit similar levels of dimorphism. Collectively, our results suggest that alternative pathways to antenna SD evolved rapidly in Anoplistes, perhaps due to different patterns of selection on tactile sensation.

Comparative morphology and key to Amydetinae genera, with description of three new firefly species (Coleoptera, Lampyridae)

Amydetinae is an exclusively Neotropical subfamily of fireflies, distributed among three genera: Amydetes Illiger, 1807, Magnoculus McDermott, 1964, and Memoan Silveira & Mermudes, 2013. Here, we describe three new species of Amydetinae: two belonging to Amydetes (A.alexi sp. nov. and A.marolae sp. nov.) and one to the previously monotypic Memoan (Me.conani sp. nov.). All three species are known only from the Atlantic Forest in southeastern Brazil. Endoskeletal structures of Memoan and Magnoculus species are described and compared with those of Amydetes for the first time. After studying the type material, Photinusfruhstorferi Pic, 1942 is transferred to Memoan, generating Memoanfruhstorferi comb. nov., and Me.ciceroi Silveira & Mermudes, 2013 syn. nov. is placed as a junior synonym. We also redescribe Magnoculusobscurus Olivier, 1885 and compare it to other species of genus and to other amydetine taxa to identify potential new diagnostic traits for the Amydetinae and its constituting genera. We provide an updated diagnosis for Memoan, illustrations for all four species, and a distribution map for the three new species, as well as a key to adult males of the three amydetine genera, and an updated key to Amydetes species based on males.

Characterization of the First Complete Mitochondrial Genome of Cyphonocerinae (Coleoptera: Lampyridae) with Implications for Phylogeny and Evolution of Fireflies

Complete mitochondrial genomes are valuable resources for phylogenetics in insects. The Cyphonoceridae represents an important lineage of fireflies. However, no complete mitogenome is available until now. Here, the first complete mitochondrial genome from this subfamily was reported, with Cyphonocerus sanguineus klapperichi as a representative. The mitogenome of C. sanguineus klapperichi was conserved in the structure and comparable to that of others in size and A+T content. Nucleotide composition was A+T-biased, and all genes exhibited a positive AT-skew and negative GC-skew. Two types of tandem repeat sequence units were present in the control region (136 bp × 2; 171 bp × 2 + 9 bp). For reconstruction of Lampyridae's phylogeny, three different datasets were analyzed by both maximum likelihood (ML) and Bayesian inference (BI) methods. As a result, the same topology was produced by both ML analysis of 13 protein-coding genes and 2rRNA and BI analysis of 37 genes. The results indicated that Lampyridae, Lampyrinae, Luciolinae (excluding Emeia) were monophyletic, but Ototretinae was paraphyletic, of which Stenocladius was recovered as the sister taxon to all others, while Drilaster was more closely related to Cyphonocerinae; Phturinae + Emeia were included in a monophyletic clade, which comprised sister groups with Lampyridae. Vesta was deeply rooted in the Luciolinae.

Cretophengodidae, a new Cretaceous beetle family, sheds light on the evolution of bioluminescence

Bioluminescent beetles of the superfamily Elateroidea (fireflies, fire beetles, glow-worms) are the most speciose group of terrestrial light-producing animals. The evolution of bioluminescence in elateroids is associated with unusual morphological modifications, such as soft-bodiedness and neoteny, but the fragmentary nature of the fossil record discloses little about the origin of these adaptations. We report the discovery of a new bioluminescent elateroid beetle family from the mid-Cretaceous of northern Myanmar (ca 99 Ma), Cretophengodidae fam. nov. Cretophengodes azari gen. et sp. nov. belongs to the bioluminescent lampyroid clade, and would appear to represent a transitional fossil linking the soft-bodied Phengodidae + Rhagophthalmidae clade and hard-bodied elateroids. The fossil male possesses a light organ on the abdomen which presumably served a defensive function, documenting a Cretaceous radiation of bioluminescent beetles coinciding with the diversification of major insectivore groups such as frogs and stem-group birds. The discovery adds a key branch to the elateroid tree of life and sheds light on the evolution of soft-bodiedness and the historical biogeography of elateroid beetles.