Systematic Entomology

The ichneumonid subfamily Eucerotinae has been thought to be almost absent from the tropics, with the only known Afrotropical species found in Madagascar. We report the subfamily to be present in the mainland Afrotropics, and describe a new species, Euceros species 1 from Uganda and Cameroon (name not yet shown in preprint). The subfamily had likely not been observed in the mainland Afrotropics before due to low abundances and insufficient sampling. More Eucerotinae likely remain to be discovered in tropical Africa and Asia, although tropical America may genuinely have few eucerotine species. Much more extensive sampling will be needed before it is possible to make confident estimates of how eucerotine diversity is distributed globally.

Understanding how global biodiversity patterns arise is a central theme of biogeography, with contemporary theory recognising the roles of both dispersal and vicariance. Genera that are broadly distributed can provide important systems for disentangling the relative influence of these processes across evolutionary timescales. However, many lesser-studied groups, particularly those in the tropics, lack a densely sampled phylogeny which hinders robust inference of their evolutionary and biogeographic history. This study investigates the global diversification and systematics of the putative pantropical moth genus Parasa Moore (Lepidoptera: Limacodidae), with the aim of assessing the relative importance of dispersal and vicariance in shaping its distribution. Medium-coverage whole genome sequencing of specimens predominantly from museum collections were used to generate a globally sampled time-calibrated phylogeny of Parasa and associated genera (the Parasa-complex). Ancestral range estimation analyses were employed to infer geographical origins and possible dispersal times between bioregions. The Parasa-complex originated in Africa in the late Oligocene ([~]24 Ma) and, through a series of long-distance dispersal events during the early-mid Miocene, expanded into Asia ([~]23 Ma) and the Americas ([~]21 Ma). Across all regions, dispersal was the dominant process shaping present-day distributions, with a limited role of vicariance in some subregions. Phylogenetic analyses further demonstrated that Parasa is not monophyletic, with multiple independent lineages contributing to its apparent pantropical distribution. These findings highlight a central role of long-distance dispersal in generating certain global distributions. The results support a dynamic model of range evolution involving rapid Miocene dispersal and subsequent regional diversification. In addition, the non-monophyly of Parasa requires substantial taxonomic revision, underscoring the importance of robust phylogenetic frameworks for interpreting global biodiversity patterns.

Our study provides the first comprehensive karyotype evolution analysis of the insect order Zoraptera. We present karyotypic descriptions of seven species across two families: Zorotypidae (Usazoros hubbardi and two Zorotypus spp.) and Spiralizoridae (Centrozoros gurneyi, Spiralizoros magnicaudelli, and two Spiralizorose spp.). These results facilitate a critical evaluation of existing cytogenetic knowledge in Zoraptera and the evolution of karyotypic traits across Polyneoptera. Most notably, we refute the presence of holocentric chromosomes in Zoraptera. Also, we show that the XY sex chromosome system is prevalent and likely ancestral within the order. Furthermore, by integrating the chromosome numbers of the studied species with a dated molecular phylogeny of Zoraptera, we provide the first estimation of the mode of chromosome number evolution for this group. Finally, standard karyotypic features (2n, chromosome morphology, and size) and the distribution of 18S rDNA and (TTAGG) telomeric motif clusters--detected by fluorescence in situ hybridization--reveal highly differentiated karyotypes and genomic structures. This genetic diversity contrasts sharply with the recognized morphological uniformity of Zoraptera.

1The measurement of visual fields in arachnology has a long-standing history. Given the wide variety of eye positions, orientation and structure, the topic is fundamental for studies of taxonomy, evolution, ecology and behavior. The existing methods for measuring visual fields deploy ophthalmoscopic measurements, which require custom microscopes, anatomical structures like the reflective tapetum, which may not always be present, or the capacity to detect photoreceptor autofluorescence. Here we present the ctSpyderFields python package: a tool for geometrically predicting the visual fields of arachnids from digital images of the lens and retina. The tool uses images coming from computed tomography (CT) scans of specimens, but could be applied to other 3D microscopy techniques, to virtually project the boundaries of the retina through the geometrically predicted nodal point of the lens, deriving a rough per-eye visual field both in cartesian and spherical coordinates. The extracted data can then be used to calculate likely visual field overlap between eyes and angular spans, which can be compared within or between species. We also provide a use case, reporting the visual field data extracted from a museum specimen of Philaeus crysops. We propose that the tool will allow a wider comparative analysis of visual fields across spider species, unlocking the potential for a deeper understanding of visual ecology and evolution.

The preparation of multi panel figures remains a labor intensive step in scientific publication. Albeit there are specific tools available to solve this problem, they are often highly specialized, difficult to install, or time consuming to learn. Griphus is a standalone graphical application designed for rapid composition and experimentation with multi panel figures, developed by and for zoological taxonomists. Functions specifically designed for multi panel composition include automatic figure numbering and placement, aspect ratio operations, spacers, layout rotation, layout suggestions, and automatic generation of figure legends, including scale bar descriptions. The software can perform both spatial interpretation of images on the canvas and work with a simple, editable layout formula. It also enables instant multi panel composition, with numbered images and automatic contrast selection for the numbers, obtained simply by loading images. User defined parameters such as target printable dimensions, resolution, spacing, and color mode are preserved throughout the work. The program produces coordinated outputs consisting of the final composite figure, a readable file describing the layout structure, and a .gri file storing images, transformations, and parameters for exact regeneration. Griphus is intended as a complementary tool to professional image software, providing a simple and efficient environment for constructing high quality multi panel figures.

This investigation aimed at compiling all phylogenetic lineages within and around genus Cyanoboletus. The evolutionary inference obtained from the nuclear ribosomal genes internal transcribed spacer region (ITS) suggests that part of the species currently classified in Cyanoboletus belong in lineages separate from the genus, thus suggesting a narrower boundary that includes only the species that develop a strong staining reaction to touch and to air exposure of the context. The separate lineages are the monotypic Cupreoboletus genus and a few species that do not develop such reaction, which are part of a clade together with genera Cacaoporus and Acyanoboletus, thus broadening the concept of Cacaoporus to encompass all of them. The emerging 3C perspective of Cupreoboletus, Cacaoporus and Cyanoboletus offers a remarkably consistent morphological diagnosis, overcoming the problems of a too broad concept for Cyanoboletus. This work reveals that Boletus neotropicus, B. novae-zelandiae and B. sensibilis belong respectively in Cyanoboletus, Cacaoporus and Lanmaoa, and by studying multigene alignment concatenates it identifies lineages that probably represent undescribed species: at least four in Cacaoporus and at least five in Cyanoboletus. Diagnostic tables and dichotomic keys are presented by geographic region. The present work also includes a study of the phylogenetic position of Neoboletus flavosanguineus, a species once classified in Cyanoboletus. The complexity of assigning species epithets in some lineages is addressed, namely for the boundaries between Cacaoporus instabilis and Ca. fagaceophilus as well as the diversity under the names Cyanoboletus sinopulverulentus and Cy. pulverulentus. The overall picture of evolutionary lineages sets a framework for the choice of reference data that can provide, in future phylogenetic studies that involve the 3C, a balanced and efficient coverage. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=197 SRC="FIGDIR/small/724631v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@7f618corg.highwire.dtl.DTLVardef@dd6a14org.highwire.dtl.DTLVardef@5f7399org.highwire.dtl.DTLVardef@9e7443_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundMosquito-borne diseases transmitted by Aedes aegypti and Aedes albopictus -- including dengue, Zika, chikungunya, and yellow fever -- depend critically on rapid and accurate vector identification. Although deep learning has achieved high accuracy on curated laboratory images, performance degrades substantially when applied to community-submitted photographs that vary widely in quality, framing, and background. We sought to develop a robust pipeline for distinguishing these two morphologically similar vectors from real-world citizen-science images. MethodsWe compiled 2,112 mosquito images from the Global Mosquito Observation Database (GMOD) and assembled a multi-stage pipeline comprising: (i) a binary classifier to screen for mosquito presence; (ii) a YOLO-based object detector to localize specimens; (iii) an image-quality assessment module evaluating brightness, sharpness (Laplacian variance), contrast, and bounding-box ratio; (iv) Segment Anything Model (SAM) segmentation to isolate specimens from background clutter; and (v) a YOLO classifier trained on binary segmentation masks. To target the diagnostic characters used in conventional morphological taxonomy, we refined the pipeline to focus detection on the thoracic scutum -- the region bearing the lyre-shaped pale-scale pattern of Ae. aegypti and the median white stripe of Ae. albopictus. ResultsBaseline YOLO classification on raw images achieved 30.95% accuracy for Ae. aegypti and 78.4% for Ae. albopictus, reflecting strong class imbalance and background noise. Augmentation alone provided only modest gains. The presence/absence classifier reached 90.52% accuracy, and the object detector localized mosquitoes with near-perfect precision. Whole-body SAM-mask classification improved overall accuracy to 68.21%. Refining the pipeline to scutum-focused classification yielded preliminary accuracies of 87.5% and 83.3% for Ae. albopictus and Ae. aegypti, respectively. ConclusionsCommunity-sourced mosquito images, despite substantial noise and inconsistency, can support automated species-level vector surveillance when paired with a domain-informed, multi-stage deep-learning pipeline. Aligning machine attention with the morphological characters used by entomologists -- via scutum-focused detection -- delivers meaningful accuracy gains. This framework supports scalable citizen-science vector monitoring and lays the groundwork for integrating high-fidelity three-dimensional reference libraries to further strengthen real-world classifier performance.

0.O_LIMorphological traits such as floral area and body size are fundamental to ecological research, serving as inputs for studies of pollinator-plant interactions, habitat quality, and biodiversity monitoring. However, accurately measuring these traits from images remains challenging, particularly in complex field conditions where existing tools exhibit reduced accuracy and limited generalizability across taxa. C_LIO_LIWe present EcoMorph, a modular morphological measurement system that leverages the Segment Anything Model 3 (SAM3) to quantify traits across diverse ecological contexts. Unlike task-specific segmentation models requiring domain-specific training data, SAM3s prompt-based architecture enables segmentation of arbitrary biological structures from natural-language prompts, using the same underlying model across flowers, insects, and other targets without retraining. From the resulting segmentations, EcoMorph extracts three classes of measurement: area, linear dimensions, and object counts. C_LIO_LIWe validated EcoMorph across two ecological scales. At the intermediate scale, EcoMorph-derived floral area agreed closely with manual ImageJ measurements (R2 = 0.935, n = 74) under simple-background conditions and (R2 = 0.928, n = 58) under complex-background conditions, with valid predictions for 95% of images. At the fine scale, EcoMorph-derived insect body area was strongly correlated with hand-measured intertegular distance (r = 0.810, n = 349), capturing body-size variation across species from the small Bombus impatiens to the large Xylocopa virginica. Object counts matched manual counts almost exactly for well-separated insects in an insect box (R2 = 0.9997, n = 12). C_LIO_LIBy combining prompt-based segmentation with modular measurement, EcoMorph enables high-throughput quantification of area, size, and abundance from heterogeneous image sources without taxon-specific training. This generality supports a broad range of ecological applications, including pollinator and plant trait research, biodiversity and abundance monitoring, and allometric biomass estimation. C_LI

Chaetognathifera, a superphylum comprising Syndermata (Rotifera including Acanthocephala), Micrognathozoa, Gnathostomulida and Chaetognatha, is a complex grouping generally recovered as the sister to all other Lophotrochozoa. However, phylogenetic relationships within this group are controversial, in part due to poor sampling, resulting in two key questions. The first is whether Gnathostomulida or Chaetognatha represent the sister group to Syndermata+Micrognathozoa. The second is the phylogenetic position of the former phylum Acanthocephala within Syndermata. Here, we present the first study of the phylogenetic affinities of Chaetognathifera with genomic representation from all major phyla, and explore the potential of macrosynteny to better understand these relationships. For this latter aspect, we also developed a new jackknifing procedure to assess the robustness of linkage groups inferred by macrosyntenic analyses. We show that the phylogenetic relationships between these clades are corroborated through a variety of gene selection and analysis methodologies. This provides clear evidence of Acanthocephala as a derived clade within Syndermata as sister to Seisonidea, and that Gnathostomulida is sister to Syndermata+Micrognathozoa, with Chaetognatha as the earliest diverging clade within Chaetognathifera. On the other hand, we found that macrosyntenic patterns cannot resolve this question. Moreover, almost all possible linkage groups involving chaetognathiferan species lack robusticity and hence, should not be considered reliable. As a consequence so far, in Chaetognathifera none of the bilaterian ancestral linkage groups can be reliably found and independent massive chromosomal rearrangements occurred. We therefore strongly suggest that studies of macrosynteny should not only assess the significance of possible linkage groups, but also the robusticity of these linkage group inferences. Furthermore, we also present a script for this purpose, which can be found at: https://github.com/JFFleming/MacrosyntenicJackknife

Silk glands have been found in two groups of amphipods: the Corophiida and the Ampeliscidae. The silk glands in Ampeliscidae, however, have yet to be examined in detail. Here we report, for the first time, the morphology and distribution of pereopodal glands in the Ampeliscidae, in non-thread producing Synopiidae, and in the Paragammaropsidae. In the Ampeliscidae we found two gland types distributed throughout all pereopods which have the ability to create threads. Pereopods three and four have additional silk extrusion morphology at the tip of the dactylus in which silk is transformed into semi-cylindrical threads used for building domiciles. Synopiid outgroup species have one of the gland types but lack silk extrusion morphology. Using ancestral state reconstruction analysis, we find that glands in the Synopiidae are likely ancestral and hypothesize that silk glands in Ampeliscidae are derived from these ancestral glands. Silk-spinning pereopods in the Paragammaropsidae had similarities with both Corophiida and Ampeliscidae but had distinctions. Ampeliscidae silk-spinning systems bear surprising resemblance to the Corophiida which presents one to reconsider the taxonomic placement of Ampeliscidae and the origins of silk-spinning in amphipods. This is the first comprehensive study on the glandular systems of Ampeliscidae, Synopiidae, and Paragammaropsidae using advanced microscopy, providing pertinent morphological data to the study of arthropod silk gland evolution and complex traits.

The Hesperiine genus Atrytonopsis Godman, 1900, occurs broadly across the American Southwest. Atrytonopsis margarita (Skinner, 1913) and Atrytonopsis python (W. H. Edwards, 1882) have look-alike appearances, concurrent flights, and geographic distributions which converge in New Mexico. Their similar wing markings and intertwined taxonomic history has made it challenging to fully understand the identity and occurrence of each. Burns (2015) revealed differences in genitalia, clarifying that they are distinct species. Genomic DNA analysis of more than 100 specimens now illuminates their genetic uniqueness, phylogenetic relationship, field identification challenges and details of their geographic distributions.

The tribe Spermacoceae (Rubiaceae) comprises a morphologically diverse assemblage of approximately 1,400 species distributed across the Neotropics, Africa, Asia, Australia, and Pacific region. It remains one of the most taxonomically intractable groups in the family, with generic limits repeatedly redefined for more than two centuries. Previous phylogenetic studies based on a limited number of plastid and nuclear markers left numerous relationships unresolved and provided sparse representation of Neotropical lineages. Here, we present the first phylogenomic study of the tribe based on plastome-scale data and expanded sampling of Neotropical taxa. We sampled 121 species representing 55 genera spanning all major clades and generated 123 new plastomes, including 25 species incorporated into a molecular phylogenetic framework for the first time. Maximum-likelihood and Bayesian analyses recovered a highly resolved and strongly supported phylogeny, with uncertainty restricted to a small number of deep backbone nodes. Pollen and seed micromorphology provided additional evidence for evaluating phylogenetic relationships. The resulting phylogenetic framework clarifies generic boundaries across several problematic lineages and supports multiple taxonomic changes. Pervasive homoplasy in seed and floral characters rendered several traditionally recognized genera non-monophyletic, warranting new combinations, including Edrastima oxycoccoides, Stenotis alexanderae, and S. prostrata, and a reassessment of taxa such as Terrellianthus serpyllaceus and Oldenlandia dusenii. We further identify genera requiring additional study and provide an updated key to the 82 recognized genera of Spermacoceae. Together, these results provide the most robust phylogenetic framework yet available for the tribe and establish a foundation for future systematic, biogeographic, and evolutionary research.

Zingiberales includes eight morphologically distinctive families, but its family-level backbone has remained unstable, especially around Musaceae, Heliconiaceae, Lowiaceae, and Strelitziaceae. We analysed 1566 low-copy nuclear genes from 52 samples, representing all eight families and Pontederia crassipes as outgroup. Concatenated maximum likelihood and multispecies coalescent analyses recovered the same backbone: ((Zingiberaceae, Costaceae), (Cannaceae, Marantaceae)) is sister to (Musaceae, (Heliconiaceae, (Lowiaceae, Strelitziaceae))). Penalized-likelihood dating placed the sampled crown group in the Late Cretaceous, with several deep family-level divergences occurring on short internodes. Analysis of 1248 rerooted gene trees showed that conflict is concentrated on these deep branches and in several shallow clades. HyDe tests of empirical and simulated matrices, each including 62,475 triples, did not support widespread ancient hybridization among the major family-level lineages after filtering against the simulated null model. The nuclear data recover a stable Zingiberales backbone, and the long-standing instability of several deep nodes is best explained by rapid early divergence and extensive incomplete lineage sorting.

Collembola (springtails) are among the most abundant and ecologically important soil arthropods, representing one of the oldest extant terrestrial hexapod lineages, with a fossil record extending to the early Devonian. Despite their relevance, phylogenetic relationships among the four extant orders (Entomobryomorpha, Poduromorpha, Symphypleona, and Neelipleona) have remained unresolved for over two decades. Here, we present the most comprehensive phylogenomic analysis of Collembola to date, comprising 1,127 single-copy orthologues from 145 taxa representing 19 families. To improve orthology inference, we developed a novel HMM-based filtering pipeline that significantly reduced hidden paralogy in BUSCO-derived datasets. Across multiple dataset configurations, gene-jackknife replicates, and various maximum-likelihood analyses, we consistently recovered Poduromorpha as the earliest-diverging lineage. Coalescent-based methods instead highlighted discordant arrangements characterised by extremely short internal branches and low quartet support, a pattern consistent with pervasive incomplete lineage sorting and reticulate evolutionary history. We further dissected the phylogenetic signal by exhaustively evaluating all possible inter-order topological arrangements, both on the full concatenated dataset and gene-by-gene, to identify the most phylogenetically informative loci. These analyses rejected the great majority of previously proposed hypotheses, narrowing support to only two statistically indistinguishable topologies (T11 and T4), with the Poduromorpha-first arrangement consistently favoured across both site-homogeneous and site-heterogeneous substitution models. Finally, with molecular dating, we estimated the origin of crown Collembola in the Early Devonian, with the diversification of the extant orders in the Carboniferous. Several extant genera were estimated to be older than many currently recognized families, highlighting the exceptional evolutionary persistence of springtail lineages and suggesting that lineage longevity should be considered when interpreting higher-level taxonomic diversity.

Conservation strategies for at-risk species can be aided significantly by research on topics such as ecology, life history, and threats, yet research effort is lacking for many species facing elevated extinction risk. Here we investigated whether listing under the U.S. Endangered Species Act (ESA) was associated with research effort for U.S. butterflies, and whether that effort was higher before or after ESA listing. We found that ESA-listed species had significantly more peer-reviewed publications than non-listed species after accounting for species range and taxonomic family. Further, we showed that more papers were published per year after ESA listing than before. These findings confirm that ESA-listed species benefit from greater research attention that can support data-informed conservation efforts. However, the relative scarcity of studies prior to ESA listing, as well as the lack of research for many unlisted, at-risk taxa, underscores the need for proactive, strategic research effort to inform conservation action.

The Dinaric karst of Croatia encompasses a network of over 10,000 caves and represents one of the worlds most important subterranean biodiversity hotspots. It is inhabited by remarkably diverse and often endemic species, including planarian flatworms, which are among the rarest macroinvertebrates encountered in cave habitats. Although the presence of cave planarians has long been known, no integrative research on this group has been conducted to date, and the evolutionary relationships between these animals and their surface water counterparts are currently unresolved. To address these gaps, we combined field sampling, phylogenetic analysis based on COI and 18S genes, and phenotypic characterization. Our results show that cave planariids in Croatia belong to at least three genera and are more widespread and diverse across both Croatia, and the broader Dinaric karst, than previously assumed. We increased the number of cave records in the Dinaric karst from 26 to 37 and documented cf. Atrioplanaria and Phagocata in Croatian caves for the first time. Phylogenetic reconstructions suggest numerous independent cave colonization events, including multiple instances within the genera Crenobia and cf. Atrioplanaria. Variation in pigmentation and eye reduction, both within and between populations, further reveal heterogeneous evolutionary trajectories of cave-associated phenotypes. The biogeographical patterns and high genetic diversity we report here point to a complex evolutionary history of planariids in the Dinarides. Our newly generated molecular phylogenies and systematic documentation of trait variability establish Planariidae as a valuable model for studying mechanisms underlying convergent evolution of pigment loss and eye reduction in cave environments.

Monocaul Ardisia (Primulaceae) have a single, vertical, woody stem and spiral phyllotaxy. They range from 30 cm to 100 cm tall. Three species of this architectural group, Ardisia mayumbensis, A. hallei and A. bracteata, have been recorded from Gabon hitherto. In this taxonomic revision we show that A. mayumbensis does not occur in Gabon, and we describe three new species. Two of these, Ardisia doudou sp. nov.and A. mica sp.nov., are endemic to Gabon and one, A. litterbin sp.nov, is found in both Gabon and Republic of the Congo. Ardisia hallei and A. bracteata are redescribed. All five species have a litter-gathering habit with a terminal funnel of leaves, and two of these species, Ardisia doudou and Ardisia litterbin, also possess adventitious roots in the distal part of the stem, a well-established strategy found in litter-gathering forest species of other plant families in tropical Africa. We provisionally assess the conservation status of all five taxa using the 2012 IUCN standard, finding that all monocaul Ardisia in Gabon fall within threatened categories. Two of the species, Ardisia bracteata and A. mica, are known from single collections and have not been seen for 164 and 63 years respectively and are conceivably extinct although further surveys are needed to establish this. We employ new characters in delineating and describing African Ardisia using leaf thickness and oil gland data.

Mosquitoes are classified into two subfamilies, each monophyletic, and typically considered to both be ancient, having diverged more than 100 million years ago based on previous divergence analyses. A recent publication challenged this view with phylogenomic results primarily from the third codon position and UCEs. Utilizing alternative fossil placement and these phylogenomic data, these authors find that the Culicidae and Chaoboridae diverged in the lower Cretaceous, and that one mosquito subfamily, the Anophelinae, is nested within the Culicinae. These results are in stark contrast to previous results from diverse data sources, ranging from other genomic data, to morphology, to fossils. Here, we briefly detail the substantial evidence that supports two monophyletic subfamilies of extant mosquitoes, along with fossil evidence that supports the ancient divergence of these lineages.

The absence of a scalable system for organizing the vast majority of unidentified species becomes the central obstacle in biodiversity science. Existing molecular and computer-vision methods rely on DNA material or closed-set labels, which hamper biodiversity quantification under the open, incomplete conditions that characterize real ecosystems. Here, we introduce morphOTUs, a general image-based framework that constructs operational units of biodiversity directly from phenotype. Using morphOTU, we derive image-based OTUs across five plant and beetle datasets spanning heterogeneous imaging conditions. These units recover species-level boundaries, retain coherent structure when most species are "unseen" during training, and accurately approximate richness and Shannon diversity indices even under sparse labeling or limited sampling. Visual explanations reveal that morphOTU consistently focuses on biologically meaningful traits and captures continuous phenotypic variation. By providing a scalable and open-set framework for quantifying phenotypic diversity, morphOTUs enable biodiversity assessment that includes unnamed species and unlock the ecological value of rapidly expanding digital image repositories.

Eye loss has long fascinated evolutionary biologists and occurs across the animal kingdom. Spiders have two parallel visual systems -- two primary and six secondary eyes -- but eye losses, leaving six, four, two, or no eyes, have occurred in multiple lineages. Despite their significance, reports of eye loss are scattered, limiting broader analysis. Here we present the first comprehensive analysis of eye loss across all known spider lineages. We show that eye loss occurs in [~]12% of extant species, mainly within the clade Synspermiata. Six-eyed spiders are most common (>5,300 species), while four-eyed, two-eyed, and eyeless forms are rarer and often linked to troglobitic lifestyles. Principal eye loss is widespread, occurring in 49 families across nearly all major lineages. Using a recent phylogeny of the order Araneae, we demonstrate a strong correlation between eye loss and occupancy of low-light environments, but this is complicated by differential effects across eye types and phylogenetic groups through geological time. These findings reveal striking lability in eye number and lay groundwork for future research into ecological, developmental, and neurological drivers of eye loss. [hidden Markov models, ancestral state reconstruction, Araneae, discrete character evolution, principal eyes, secondary eyes, low light environments].