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Factors regulating larval growth and determinants of adult body size are described for several holometabolous insects, but less is known about brain size scaling through development. Here we use the isotropic fractionation ("brain soup") method to estimate the number of brain cells and cell density for the whitelined sphinx moth (Lepidoptera: Hyles lineata) from the first instar through the adult stage. We measure mass and brain cell number and find that, during the larval stages, body mass shows an exponential relationship with head width, while the total number of brain cells increases asymptotically. Larval brain cell number increases by a factor of ten from nearly 8000 in the first instar to over 80,000 in the fifth instar. Brain cell number increases by another factor of 10 during metamorphosis, with the adult brain containing more than 900,000 cells. This is similar to increases during development in the vinegar fly (Drosophila melanogaster) and the black soldier fly (Hermetia illucens). The adult brain falls slightly below the brain-to-body allometry for wasps and bees but is comparable in the number of cells per unit brain mass, indicating a general conservation of brain cell density across these divergent lineages. 

Abstract Automeris moths are a morphologically diverse group with 135 described species that have a geographic range that spans from the New World temperate zone to the Neotropics. Many Automeris have elaborate hindwing eyespots that are thought to deter or disrupt the attack of potential predators, allowing the moth time to escape. The Io moth (Automeris io), known for its striking eyespots, is a well-studied species within the genus and is an emerging model system to study the evolution of deimatism. Existing research on the eyespot pattern development will be augmented by genomic resources that allow experimental manipulation of this emerging model. Here, we present a high-quality, PacBio HiFi genome assembly for Io moth to aid existing research on the molecular development of eyespots and future research on other deimatic traits. This 490 Mb assembly is highly contiguous (N50 = 15.78 mbs) and complete (benchmarking universal single-copy orthologs = 98.4%). Additionally, we were able to recover orthologs of genes previously identified as being involved in wing pattern formation and movement. 

Temporal ecological niche partitioning is an underappreciated driver of speciation. While insects have long been models for circadian biology, the genes and circuits that allow adaptive changes in diel-niches remain poorly understood. We compared gene expression in closely related day- and night-active non-model wild silk moths, with otherwise similar ecologies. Using an ortholog-based pipeline to compare RNA-Seq patterns across two moth species, we find over 25 pairs of gene orthologs showing differential expression. Notably, the genedisco,involved in circadian control, optic lobe and clock neuron development inDrosophila, shows robust adult circadian mRNA cycling in moth heads.Discois highly conserved in moths and has additional zinc-finger domains with specific nocturnal and diurnal mutations. We proposediscoas a candidate gene for the diversification of temporal diel-niche in moths. 

Abstract The sphinx moth genus Hyles comprises 29 described species inhabiting all continents except Antarctica. The genus diverged relatively recently (40–25 MYA), arising in the Americas and rapidly establishing a cosmopolitan distribution. The whitelined sphinx moth, Hyles lineata, represents the oldest extant lineage of this group and is one of the most widespread and abundant sphinx moths in North America. Hyles lineata exhibits the large body size and adept flight control characteristic of the sphinx moth family (Sphingidae), but it is unique in displaying extreme larval color variation and broad host plant use. These traits, in combination with its broad distribution and high relative abundance within its range, have made H. lineata a model organism for studying phenotypic plasticity, plant–herbivore interactions, physiological ecology, and flight control. Despite being one of the most well-studied sphinx moths, little data exist on genetic variation or regulation of gene expression. Here, we report a high-quality genome showing high contiguity (N50 of 14.2 Mb) and completeness (98.2% of Lepidoptera BUSCO genes), an important first characterization to facilitate such studies. We also annotate the core melanin synthesis pathway genes and confirm that they have high sequence conservation with other moths and are most similar to those of another, well-characterized sphinx moth, the tobacco hornworm (Manduca sexta).