Group Of Arachnids Research Articles

Checklist of Water mites in Mexico. Historical background and DNA barcoding perspectives

Water mites are the most ubiquitous, abundant, diverse, and ecologically important group of arachnids in all freshwater environments. In Mexico, despite being a megadiverse country, only 271 species have been recorded so far since 1873. This is probably due to the scarcity of taxonomists in the country or the inherent complex morphology of this group, which challenges its systematics and its integration into other research studies. Molecular identification has been highly useful for practical applications of these organisms, while taxonomic identification work continues. Until now, a species checklist and reference information about water mites diversity and distribution in Mexico is lacking. In this work, we compiled species described or recorded in Mexico and provided preliminary data for a COI barcode library of the water mites in the country. This checklist includes 271 species from 25 families and 61 genera. In addition, the COI barcode library is supplied in a public dataset from the BOLD database (boldsystems.org); it contains 794 sequences corresponding to 103 BINs or putative species, of which only five of them have been identified to the species. We predict that the discovery of hidden diversity of mites will continue and improve after the use of integrative taxonomy tools. Also, their value as indicators of water quality will be re-evaluated, helping in the conservation of freshwater environments and the evaluation of the global warming impact.

Unveiling the Genetic Blueprint of a Desert Scorpion: A Chromosome-level Genome of Hadrurus arizonensis Provides the First Reference for Parvorder Iurida.

Over 400 million years old, scorpions represent an ancient group of arachnids and one of the first animals to adapt to life on land. Presently, the lack of available genomes within scorpions hinders research on their evolution. This study leverages ultralong nanopore sequencing and Pore-C to generate the first chromosome-level assembly and annotation for the desert hairy scorpion, Hadrurus arizonensis. The assembled genome is 2.23 Gb in size with an N50 of 280 Mb. Pore-C scaffolding reoriented 99.6% of bases into nine chromosomes and BUSCO identified 998 (98.6%) complete arthropod single copy orthologs. Repetitive elements represent 54.69% of the assembled bases, including 872,874 (29.39%) LINE elements. A total of 18,996 protein-coding genes and 75,256 transcripts were predicted, and extracted protein sequences yielded a BUSCO score of 97.2%. This is the first genome assembled and annotated within the family Hadruridae, representing a crucial resource for closing gaps in genomic knowledge of scorpions, resolving arachnid phylogeny, and advancing studies in comparative and functional genomics.

Identifying insect and arachnid indicator taxa for impacts and management in coastal landscapes

Insects and arachnids are abundant and diverse, respond to key human impacts and support a diversity of key ecological functions. They are therefore widely recognised as effective surrogates for ecosystem condition. Their efficacy as indicators and surrogates in coastal dunes has, however, rarely been quantified, but might be instructive in guiding management in these often highly impacted coastal ecosystems. In this study, we (1) tested the effects of spatial and habitat drivers on the abundance of key insect and arachnid groups, and (2) used these patterns to identify viable management surrogates for impacts and management actions. We surveyed insect, arachnid and plant assemblages in coastal dunes at 20 sites on the Sunshine Coast in central eastern Australia. We have identified indicators for habitat condition and indicators for impact, and taxa that could be used to measure restoration outcomes. Crucially, five indicator groups also met criteria for being umbrella species, as management actions that increase their abundance would confer benefits to most other insect and arachnid taxonomic groups. We identified seven indicator groups (five insect and two arachnid), and each were affected by multiple spatial and habitat metrics, with metrics quantifying the composition and structure of vegetation communities being the most important predictors of most indicator’s distributions. Implications for insect conservation: We highlight the importance of understanding subtleties in spatial patterns and the unique set of spatial and environmental conditions that each group requires when identifying suitable indicator taxa for use in the conservation and management of coastal dunes.

Habitat of two threatened short-tailed whip-scorpions (Arachnida: Schizomida) in the tropical Andes of Northern South America

AimSchizomids are one of the less-known arachnid groups in terms of their natural history and ecology. However, due to their remarkable short-range endemic distribution, they may be vulnerable to climate change and habitat loss. In Colombia, although the national IUCN red list of threatened invertebrates has categorized species of schizomids as vulnerable (VU), this assessment was based on expert criteria. Therefore, information about the ecology of schizomids is critical for a more accurate reassessment of their conservation status. In this study, we describe the habitat of two species of Surazomus in endangered Andean tropical forests of Colombia after a sampling effort of 15.12 m2 (n = 168 soil samples) and the collection of 6999 soil fauna individuals from the samples. We analyzed soil fauna communities associated with schizomids as well as different forest and environmental variables from permanent plots installed a decade ago in the Sabana de Bogotá region. Detailed information on climate, plant communities, and forest structure was obtained from these plots. Thus, we provide the first comprehensive habitat description of schizomids including both above- and belowground compartments. We found that each species lives in specific habitats with different soil fauna communities, suggesting a potential association between geographical fidelity and habitat conditions. This result could indicate that schizomids are highly sensitive to dramatic environmental changes, such as those experienced in the Andean region of Colombia.Implications for insect conservationOur study is valuable for the future reassessment of the conservation status of schizomids in the country, particularly considering that the previous categorization was based on expert criteria. Since habitat conditions and soil fauna communities are species-specific, schizomids could be disproportionately vulnerable to climate change and human disturbances in the Colombian Andes.

A scientist’s guide to Solifugae: how solifuges could advance research in ecology, evolution, and behaviour

Abstract Despite having >1200 described species and despite their nearly worldwide distribution and prevalence in many xeric ecosystems, relative to many other arachnid groups, we know little about the natural history and behaviour of animals in the order Solifugae (camel spiders, sun spiders, sun scorpions, etc.). Here, we review the current solifuge literature through the lens of conceptual research areas in ecology, evolution, and behaviour and propose ways in which solifuges can contribute to research in specific subfields, as follows: (i) ecology: community and trophic dynamics; connecting food webs; habitat specialization; and biodiversity and conservation; (ii) evolution: speciation and diversification; activity cycles and associated traits; adaptations for speed; and living in extreme environments; and (iii) behaviour and sensory systems: sleep, quiescence, and diapause; sensory systems and sensory ecology; learning and cognition; and mating systems, sexual selection, and sexual conflict. This resource can provide a starting point for identifying research programmes that will simultaneously contribute basic natural history information about this under-studied group and provide a broader understanding of fundamental concepts and theories across the life sciences. We hope that scientists will take this review as a challenge to develop creative ways of leveraging the unique features of solifuges to advance scientific knowledge and understanding.

Miniaturization does not change conserved spider anatomy, a case study on spider Rayforstia (Araneae: Anapidae)

Miniaturization is an evolutionary trend observed in many animals. Some arachnid groups, such as spiders and mites, demonstrate a strong tendency toward miniaturization. Some of the most miniaturized spiders belong to the family Anapidae. In this study, using light and confocal microscopy and 3D modelling, we provide the first detailed description of the anatomy of a spider of the genus Rayforstia, which is only 900 µm long. In comparison with larger spiders, Rayforstia has no branching of the midgut in the prosoma and an increased relative brain volume. In contrast to many miniature insects and mites, the spider shows no reduction of whole organ systems, no allometry of the digestive and reproductive systems, and also no reduction of the set of muscles. Thus, miniature spider shows a more conserved anatomy than insects of a similar size. These findings expand our knowledge of miniaturization in terrestrial arthropods.

The largest Palaeozoic whip scorpion and the smallest (Arachnida: Uropygi: Thelyphonida); a new species and a new ichnospecies from the Carboniferous of New England, USA

Abstract Palaeozoic fossils of whip scorpions (Arachnida: Uropygi: Thelyphonida) are extremely rare, with only seven species of this age previously described. A new species of fossil whip scorpion, as well as the first ichnospecies assignable to this group, are described here from the Carboniferous Narragansett Basin of Massachusetts, USA. A body fossil from the Rhode Island Formation (Moscovian) is referred to as Parilisthelyphonus bryantae gen. nov., sp. nov.. At more than 34 mm long it represents both the largest known Palaeozoic whip scorpion and the first fossil arachnid found in the Rhode Island Formation in ~130 years of scrutiny. The whip scorpion trace fossil, comprising a full-body impression and associated tracks, is described from the subjacent Wamsutta Formation (Late Bashkirian) of Massachusetts, USA as Inmontibusichnus charleshenryturneriigen. nov., isp. nov.. With an estimated body length of less than 10 mm, the producer would be the smallest known Palaeozoic thelyphonid. These discoveries within the Narragansett Basin represent only the second site in the western hemisphere, in what was western Laurasia, to yield Palaeozoic whip scorpions. The Narragansett Basin is of significant Pangaean biogeographical importance among whip scorpion sites, being located between the westernmost Mazon Creek Lagerstätte of Illinois and the eastern assemblage of localities in Europe, and serves as an important new fossil calibration point for phylogenetic studies of this arachnid group.

Fungus and fruit consumption by harvestmen and spiders (Opiliones, Araneae): the vegetarian side of two predominantly predaceous arachnid groups

In this review, we report on harvestmen and spiders feeding on fungi, fruits, and seeds. Fungivory in harvestmen is widespread, with most reports referring to tropical species in the family Sclerosomatidae, which consume mainly small forest mushrooms (families Marasmiaceae and Mycenaceae). In contrast, consumption of fungal material by spiders apparently occurs only if airborne spores trapped in the viscid threads of orb-webs (e.g., Araneidae and Tetragnathidae) are ingested along with old webs prior to the construction of new webs. Consumption of fruit pulp by harvestmen is also widespread, with several records of Leiobunum spp. (Sclerosomatidae) feeding on Rubus spp. berries and other lipid-poor fruits in the Holarctic region. In Neotropical forests, harvestmen in the families Cosmetidae and Gonyleptidae feed on lipid-poor pulp of fallen fruits. Among spiders, we document several cases of synanthropic species opportunistically feeding on fruit waste (e.g., pieces of banana, papaya, watermelon, or orange pulp) inside houses or disposed in yards. Only one case of a spider feeding on a wild fruit in the field was found in our search. Finally, we report several cases of harvestmen and spiders feeding on elaiosomes or arils (i.e., lipid-rich seed appendages). In conclusion, harvestmen consume mushrooms, fruit pulp, seeds, and seed appendages more frequently than spiders probably because they are “solid food feeders”, which means they can ingest solid tissues by biting off small pieces. In turn, spiders are “fluid feeders” and feed on vegetable matter most frequently in the form of fluids (e.g., nectar, stigmatic exudate, plant sap, and honey dew), rather than fungal or plant tissues.

Integrative Taxonomy Approach Reveals Cryptic Diversity within the Phoretic Pseudoscorpion Genus Lamprochernes (Pseudoscorpiones: Chernetidae).

Pseudoscorpions represent an ancient, but homogeneous group of arachnids. The genus Lamprochernes comprises several morphologically similar species with wide and overlapping distributions. We implemented an integrative approach combining molecular barcoding (cox1), with cytogenetic and morphological analyses in order to assess species boundaries in European Lamprochernes populations. The results suggest ancient origins of Lamprochernes species accompanied by morphological stasis within the genus. Our integrative approach delimited three nominal Lamprochernes species and one cryptic lineage Lamprochernes abditus sp. nov. Despite its Oligocene origin, L. abditus sp. nov. can be distinguished from its closest relative only by molecular and cytogenetic differences, or alternatively, by a complex multivariate morphometric analysis involving other Lamprochernes species. The population structure and common haplotype sharing across geographically distant populations in most Lamprochernes species suggest that a phoretic manner of dispersal is efficient in this group.

Comparative analysis of mitochondrial genomes reveals family-specific architectures and molecular features in scorpions (Arthropoda: Arachnida: Scorpiones)

Scorpions are a group of arachnids with great evolutionary success that comprise more than 2,000 described species. Mitochondrial genomes have been little studied in this clade. We describe and compare different scorpion mitochondrial genomes and analyze their architecture and molecular characteristics. We assembled eight new scorpion mitochondrial genomes from transcriptomic datasets, annotated them, predicted the secondary structures of tRNAs, and compared the nucleotide composition, codon usage, and relative synonymous codon usage of 16 complete scorpion mitochondrial genomes. Lastly, we provided a phylogeny based on all mitochondrial protein coding genes. We characterized the mitogenomes in detail and reported particularities such as dissimilar synteny in the family Buthidae compared to other scorpions, unusual tRNA secondary structures, and unconventional start and stop codons in all scorpions. Our comparative analysis revealed that scorpion mitochondrial genomes exhibit different architectures and features depending on taxonomic identity. We highlight the parvorder Buthida, particularly the family Buthidae, as it invariably exhibited different mitogenome features such as synteny, codon usage, and AT-skew compared to the parvorder Iurida that included the rest of the scorpion families we analyzed in this study. Our results provide a better understanding of the evolution of mitogenome features and phylogenetic relationships in scorpions.

X-ray microtomography of the late Carboniferous whip scorpions (Arachnida, Thelyphonida) Geralinura britannica and Proschizomus petrunkevitchi

Whip scorpions (Thelyphonida) and schizomids (Schizomida) are closely related arachnid orders, whose low species diversity compared to other arachnid groups is reflected in a limited fossil record. Here we investigate two key fossil whip scorpions from the British Middle Coal Measures of Coseley, Staffordshire (late Carboniferous, c. 315 Ma), UK, using X-ray microtomography, and incorporate the taxa into an updated arachnid phylogeny. Geralinura brittanica Pocock, 1911 is an unequivocal whip scorpion, whose pedipalps are closer to the modern condition than previously assumed. The trochanter bears a dorsal flange with prodorsal teeth, and the whole pedipalp is rendered subchelate by the presence of at least a patellar apophysis. These results suggest a high degree of stasis in whip scorpions since the late Carboniferous, and the genus Geralinula Scudder, 1884 is within the crown-group; i.e. the extant family Thelyphonidae. Proschizomus petrunkevitchi Dunlop and Horrocks, 1996 lacks median eyes, a character shared with Schizomida, but unlike schizomids the pedipalp also has patellar and tibial apophyses; albeit with the appendage articulating at an angle of c. 45° rather than articulating horizontally as in living whip scorpions, or vertically as in schizomids. Our phylogeny refutes a previous hypothesis that P. petrunkevitchi is a stem-schizomid, and places it among the whip scorpions instead. However, the species may have branched early from the whip scorpion lineage, and thus its morphology might reflect a plesiomorphic arrangement in which the pedipalps were transitioning from a more leg-like to a fully raptorial and claw-like set of prey-catching appendages.

The seven grand challenges in arachnid science

This perspective identifies the grand challenges in arachnid science: 1. Grasp the arachnid species diversity. There is a need to accelerate taxonomic research to obtain a sense of arachnid species diversity, however, at the same time, taxonomy needs to increase its quality, rigor, and repeatability. 2. Standardize arachnid systematics research. A solid phylogenetic definition and morphological diagnosis of Arachnida and its composing subgroups, usually treated at the rank of order, are needed. Studies should aim to stabilize and standardize phylogenetic efforts at all levels of hierarchy, and systematists should adopt criteria for higher level ranks in arachnid classification. 3. Interpret arachnid trait evolution through omics approaches. Among the field’s grand challenges is to define the genetic diversity encoding for the diverse arachnid traits, including developmental, morphological and ecological characteristics, biomaterials such as silks, venoms, digestive fluids, or allergens and bioproducts that cause diseases. Comparative genomics, transcriptomics, and proteomics will provide the empirical basis for biotechnology to modify arachnid genomes to fit numerous applications. 4. Facilitate biotechnological applications of arachnid molecules and biomaterials. Among the grand field challenges is to define potential applications of arachnid bioproducts from therapeutics to industry. New natural and biodegradable products, e.g. from spider silks, should ease our burden on ecosystems. 5. Utilize arachnids as models in ecological and biogeographic research. Biodiversity inventory sampling and analytical techniques should be extended from spiders to other arachnid groups. Spiders and their webs could be used as environmental DNA samplers, measuring or monitoring ecosystems’ overall biodiversity. Arachnids are excellent models to address biogeographical questions at the global to local scales. 6. Disentangle evolutionary drivers of arachnid diversity. Among the field grand challenges is a more precise evaluation to what extent the emergence of arachnid phenotypes is shaped by classical selection processes, and under what conditions, if any, sexual conflict needs to be invoked. 7. Define effective conservation measures for arachnids in the light of global changes. Effective conservation measures in arachnology should integrate the data from phylogenetic diversity, physiology, ecology, biogeography, and global change biology.

Ecological aspects of Ammotrechella manggi (Solifugae: Ammotrechidae) in mangrove forest from southern Morrosquillo Gulf, Colombian Caribbean

Solifugae are a group of arachnids with strong chelicerae and absence of venom, diverse in the tropics and subtropics, tolerant to levels of humidity, and adapted to coastal ecosystems. The ecological characteristics of Ammotrechella manggi Acosta-Berrocal et al. 2017 in mangrove fragments from the southern Morrosquillo Gulf, Colombian Caribbean, were evaluated. The solifuges were collected in four fragments of mangrove forests, between November 2015 and July 2016 in different climatic seasons. A total of 81 individuals were collected, and the occurrence and abundance of solpugids in the evaluated mangrove forest fragments may be influenced by precipitation, height, and bark humidity. A. manggi exhibited a preference for fallen trees with or without decomposed areas located in floodable areas at heights between 0.5-2.7 meters and fallen trunks located on sandbars at lower heights of 1.5 m. The mangrove forest fragments offer the conditions and resources for the occurrence of the populations of A. manggi, determined by the availability of microhabitats that provide protection, shelter, and nesting sites.

Single-Island Endemism despite Repeated Dispersal in Caribbean Micrathena (Araneae: Araneidae): An Updated Phylogeographic Analysis

Island biogeographers have long sought to elucidate the mechanisms behind biodiversity genesis. The Caribbean presents a unique stage on which to analyze the diversification process, due to the geologic diversity among the islands and the rich biotic diversity with high levels of island endemism. The colonization of such islands may reflect geologic heterogeneity through vicariant processes and/ or involve long-distance overwater dispersal. Here, we explore the phylogeography of the Caribbean and proximal mainland spiny orbweavers (Micrathena, Araneae), an American spider lineage that is the most diverse in the tropics and is found throughout the Caribbean. We specifically test whether the vicariant colonization via the contested GAARlandia landbridge (putatively emergent 33–35 mya), long-distance dispersal (LDD), or both processes best explain the modern Micrathena distribution. We reconstruct the phylogeny and test biogeographic hypotheses using a ‘target gene approach’ with three molecular markers (CO1, ITS-2, and 16S rRNA). Phylogenetic analyses support the monophyly of the genus but reject the monophyly of Caribbean Micrathena. Biogeographical analyses support five independent colonizations of the region via multiple overwater dispersal events, primarily from North/Central America, although the genus is South American in origin. There is no evidence for dispersal to the Greater Antilles during the timespan of GAARlandia. Our phylogeny implies greater species richness in the Caribbean than previously known, with two putative species of M. forcipata that are each single-island endemics, as well as deep divergences between the Mexican and Floridian M. sagittata. Micrathena is an unusual lineage among arachnids, having colonized the Caribbean multiple times via overwater dispersal after the submergence of GAARlandia. On the other hand, single-island endemism and undiscovered diversity are nearly universal among all but the most dispersal-prone arachnid groups in the Caribbean.

Micro-Computed Tomography Reveals a Remarkable Twin Intromittent Organ in Spiders – A Novelty for Arachnids With Direct Sperm Transfer

The modification of male pedipalps into secondary sexual intromittent organs is one of the hallmark characteristics of spiders, yet understanding the development and evolution of male genitalia across the order remains a challenging prospect. The embolus – the sclerite bearing the efferent spermatic duct or spermophor, and used to deliver sperm directly to the female genitalia during copulation – has always been considered the single unambiguously homologous palpal sclerite shared by all spider species, fundamental to the bauplan of the order and to the evolution and functional morphology of spider reproductive systems. Indeed, after two centuries of comparative research on spider reproduction, the presence of a single spermophor and embolus on each of a male spider’s two pedipalps remains a central tenet of evolutionary arachnology. Our findings challenge this premise, and reveal a remarkable twin intromittent organ sperm transfer system in a lineage of Australian palpimanoid spiders, characterized by a bifurcate spermophor and the presence of two efferent ducts leading to a pair of embolic sclerites on each pedipalp. This is the first time such a remarkable conformation has been observed in any group of arachnids with direct sperm transfer, complicating our understanding of palpal sclerite homologies, and challenging ideas about the evolution of spider genitalia.

First record of the interaction between the arthropod-pathogenic fungus Gibellula and a new species of harvestman Auranus (Stygnidae) narrowly endemic to the Brazilian rain forest.

Harvestmen are one of the largest groups of arachnids with more than 6,500 species distributed in 1,500 genera and 50 families. However, the interactions between harvestmen and arthropod-pathogenic fungi have rarely been studied. Certain previous studies report that fungal attack represents one of the most important factors for the mortality of harvestmen, but the fungus has rarely been identified, and most of the important information about the fungus-host interactions remains unrecorded. In the present study, we have described the new species Auranus quilombola sp. nov. and reported its interactions with the arthropod-pathogenic fungus Gibellula sp. Auranus quilombola sp. nov. belongs to the family Stygnidae, and it is endemic to the humid mountain forests of Cear state, Brazil in an area of endemism known as Brejos Cearenses. The species is related to five other species of Auranus, all of which have been recorded from the Amazon rainforest. A taxonomic description of this new species and its biogeographic implications have also been discussed in this paper.

Diversification and post-glacial range expansion of giant North American camel spiders in genus Eremocosta (Solifugae: Eremobatidae)

Species of camel spiders in the family Eremobatidae are an important component of arthropod communities in arid ecosystems throughout North America. Recently, research demonstrated that the evolutionary history and biogeography of the family are poorly understood. Herein we explore the biogeographic history of this group of arachnids using genome-wide single nucleotide polymorphism (SNP) data, morphology, and distribution modelling to study the eremobatid genus Eremocosta, which contains exceptionally large species distributed throughout North American deserts. Relationships among sampled species were resolved with strong support and they appear to have diversified within distinct desert regions along an east-to-west progression beginning in the Chihuahuan Desert. The unexpected phylogenetic position of some samples suggests that the genus may contain additional, morphologically cryptic species. Geometric morphometric analyses reveal a largely conserved cheliceral morphology among Eremocosta spp. Phylogeographic analyses indicate that the distribution of E. titania was substantially reduced during the last glacial maximum and the species only recently colonized much of the Mojave Desert. Results from this study underscore the power of genome-wide data for unlocking the genetic potential of museum specimens, which is especially promising for organisms like camel spiders that are notoriously difficult to collect.

Kinematics of whip spider pedipalps: a 3D comparative morpho-functional approach.

Amblypygi are tropical and subtropical ambush predators that use elongated, raptorial pedipalps for different activities. Although pedipalp use in predation and courtship has been explored in videography in vivo analyses, kinematic ex vivo examination of these appendages has not been conducted. Here, we rectify this lack of data by using micro-CT scans to 3D-kinematically model the appendage morphology and the range of motion (ROM) of the joints for Damon medius and Heterophrynus elaphus. We illustrate the successful application of this technique to terrestrial euarthropods in determining the maximum ROM values for each pedipalp joint. We also note that, in life, these values would be lower due to motion restricting structures like tendons, arthrodial membranes, and muscles. We further compare our maximum values obtained here with data from video-based motion analyses. The ROM of each joint shows the greatest flexibility in the femur-tibia joint (140-150°), the lowest in the basitarsus-claw joint (35-40°). ROM in the tibia-basitarsus joint is markedly distinct (D. medius: 44°; H. elaphus: 105°). This disparity reflects how H. elaphus uses the joint in the capture basket, while D. medius uses the femur-tibia joint to form the capture basket. We further illustrate notable vertical motion of the H. elaphus pedipalp compared to D. medius. This difference reflects the retro-ventral trochanter apophysis of H. elaphus. Our study opens the possibility to further whip spider kinematic understanding. Examination of other taxa using this approach will result in a more comprehensive understanding of the ecological significance and ethological implications of this unique arachnid group.

More intraguild prey than pest species in arachnid diets may compromise biological control in apple orchards

Understanding the full diet of natural enemies is necessary for evaluating their role as biocontrol agents, because many enemy species do not only feed on pests but also on other natural enemies. Such intraguild predation can compromise pest control if the consumed enemies are actually better for pest control than their predators. In this study, we used gut metabarcoding to quantify diets of all common arachnid species in Swedish and Spanish apple orchards. For this purpose, we designed new primers that reduce amplification of arachnid predators while retaining high amplification of all prey groups. Results suggest that most arachnids consume a large range of putative pest species on apple but also a high proportion of other natural enemies, where the latter constitute almost a third of all prey sequences. Intraguild predation also varied between regions, with a larger content of heteropteran bugs in arachnid guts from Spanish orchards, but not between orchard types. There was also a tendency for cursorial spiders to have more intraguild prey in the gut than web spiders. Two groups that may be overlooked as important biocontrol agents in apple orchards seem to be theridiid web spiders and opilionids, where the latter had several small-bodied pest species in the gut. These results thus provide important guidance for what arachnid groups should be targets of management actions, even though additional information is needed to quantify all direct and indirect interactions occurring in the complex arthropod food webs in fruit orchards.

No risk to scrambling? Mating tactic does not affect the frequency of leg autotomy in a New Zealand harvestman

Intense sexual selection on males may drive the evolution of exaggerated weaponry, typically used in contests for females or reproductive sites. In some species, males have discontinuous variation in weapon morphology that is accompanied by alternative reproductive tactics (ARTs). Major males with enlarged weapons usually exhibit a mating tactic based on female or resource defence, which makes them relatively sedentary. Minor males with reduced or absent weapons may exhibit a scramble competition mating tactic, which involves increased movement in search of females. Thus, the main costs paid by majors involve the expression/maintenance of exaggerated structures and potential injuries during contests. In turn, the main costs paid by minors are likely related to increased exposure to predation during mate search, yet this cost has rarely been considered for minors. Harvestmen are an arachnid group with diverse male weaponry, including many cases of male polymorphism associated with ARTs. Species of the suborder Eupnoi use leg autotomy as a common antipredator defence. Here we investigated whether leg autotomy (a proxy for predation risk) is more frequent in minors of the weapon polymorphic harvestman Forsteropsalis pureora , which has three male morphs with drastically different cheliceral size and morphology. Leg autotomy was very common, with 54% of wild-caught individuals missing at least one leg (mostly leg II), but we found no evidence for differential predation risk between male morphs during adulthood. In a predator simulation experiment, we found no difference in the likelihood or latency to autotomize a leg between male morphs or leg types (legs I, II, III or IV). However, males already missing legs were more reluctant to autotomize an additional leg. Our results suggest that while leg autotomy is a common antipredator strategy, with no difference between male tactics, costs are compounded as additional legs are autotomized and males may strategically decide not to autotomize in future predator encounters. • New Zealand harvestmen autotomize (lose) legs to escape predators. • This defence strategy is common in wild populations. • Sensory legs are lost more often than locomotory legs. • Harvestmen that have lost legs in the past take longer to drop an additional leg. • Male reproductive strategy does not affect autotomy risk.