The Journal of Arachnology - 2023
Volume 51 Number 1 - pp. 1-102



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.

Updates and perspectives on reproductive behavior of South American wolf spiders


The family Lycosidae is one of the spider families with the greatest diversity of species and with varied and striking strategies. Studies on Neotropical wolf spiders have contributed new and valuable information to the field of sexual selection for several decades, having discovered cases that differ markedly from previously known patterns, not only for the family but for spiders in general. Here we provide a review of studies on reproductive biology of South American wolf spiders in recent decades, focusing on the subfamilies Lycosinae, Allocosinae and Sossipinae. The promising possibilities of the spiders of this family to test fundamental hypotheses in sexual selection and reproductive biology are highlighted, and we outline areas of particular interest for future studies. We hope that this review will inspire further studies on a broader range of wolf spider species in the Neotropics.

Featured Articles

Seasonal changes in spider diversity in subtropical riparian forests: what drives the seasonality of the araneofauna?


Spiders are usually found through all seasons in the subtropics, but little is known about their seasonality patterns and how they respond to abiotic factors, especially in species-rich regions such as Brazil. We investigated the seasonal variation in spider communities and the possible influence of abiotic factors (e.g., temperature, rainfall) on spider abundance, species richness and composition in subtropical riparian forest in four river basins. Changes in spider abundance among seasons differed between ontogenetic stages: there were more spiderlings in the autumn, and similar numbers of adults year round. Species richness, on the other hand, was highest in spring and summer. Species composition differed between seasons and river basins. Several factors may be behind diversity changes in the araneofauna among seasons, however, none of the abiotic factors evaluated showed a strong direct influence. Seasonal patterns varied, with different species having peaks in all three seasons but autumn. Seasonality is clear in these spider communities but not all patterns follow predictions from simple temperature changes.

A new species of Endangered giant trapdoor spider (Mygalomorphae: Idiopidae: Euoplos) from the Brigalow Belt of inland Queensland, Australia


A new species of giant trapdoor spider, Euoplos dignitas sp. nov. (family Idiopidae), is described from the Brigalow Belt of inland Queensland, Australia. Phylogenetic analysis of a six gene molecular dataset for the tribe Euoplini reveals that this species is sister to the spinnipes-group from eastern Queensland, and unrelated to a morphologically similar congener (E. grandis Wilson & Rix, 2019) that occurs further south in the Brigalow Belt. Both E. dignitas sp. nov. and E. grandis are very large, scopulate, plug door-building trapdoor spiders from transitional woodland habitats on vertosols (‘black soils’), with superficially similar females and strongly sexually-dimorphic ‘honey-red’ males. Information on the known biology and distribution of E. dignitas sp. nov. is summarized, and a conservation assessment is provided under the International Union for Conservation of Nature’s (IUCN) Red List Criteria, indicating that this species is likely Endangered.

A new genus of Zalmoxoidea from Colombia (Arachnida: Opiliones: Grassatores)


A new genus and species of Neotropical Grassatores, Hevelia crucis gen. et sp. nov., is described and illustrated based on material of both sexes from Colombia. After comparison with the greater groups in Zalmoxoidea, especially the putative early derivative families Guasiniidae and Icaleptidae, this new taxon is considered a Zalmoxoidea incertae sedis, and seems to be related with Trypophobica Cruz-López et al., 2021 (currently in Icaleptidae, but which should be removed from this family) and Costabrimma Goodnight & Goodnight, 1983 (currently in Zalmoxoidea incertae sedis), both from Central America. Two species currently included in the zalmoxid genus Stygnoleptes Banks, 1913 from El Salvador are transferred to Trypophobica, creating the new combinations T. gibbera (Roewer, 1954) and T. sellata (Roewer, 1954). Two morphological structures for Zalmoxoidea are named here: mons cribellatus (sexually dimorphic porous prosomal and/or abdominal dorsal hillock) and elbow-spade (lanceolate blade apical in the truncus penis).

Thermal tolerances of different life stages, sexes, and species of widow spiders (Araneae: Theridiidae)


Temperature strongly shapes the physiology and distributions of ectotherms. Environmental extremes and the range of temperatures encountered can limit persistence. Further, thermal tolerance limits are thought to be one of the factors limiting the distributions of invasive species. The critical thermal maximum (CTMax) and critical thermal minimum (CTMin) are metrics frequently applied for defining upper and lower thermal tolerances, respectively. Temperatures contained within the boundaries of the CTMax and CTMin comprise the thermal tolerance range. In this study, we tested whether thermal tolerances differed between two native (Latrodectus hesperus Chamberlin & Ivie, 1935 and L. mactans (Fabricius, 1775)) and one invasive (L. geometricus CL Koch, 1841) widow species (Latrodectus Walckenaer, 1805). We separately tested if thermal tolerances differed by life stage and sex. Using species distribution modelling, we also tested if thermal extremes or temperature range most accurately correspond with current species occurrences in the United States. We hypothesized that Latrodectus geometricus would have lower thermal tolerance range and that minimum temperatures would most influence their present distributions since they presumably originated from a more equatorial climate. We found that CTMin did not vary by developmental stage, but was highest in males. We found that the CTMin and CTMax of L. geometricus (3.2, 51.5 °C) and L. mactans (1.9, 52.4 °C) were higher than L. hesperus (-1.9, 49.6 °C). Males also had the narrowest thermal tolerance range in the three species examined. Lastly, we found that the highest performing distribution model was the one correlating minimum temperature with L. geometricus occurrences.

Aliens in the society: foreign arthropods and small vertebrates associated with the social spider Stegodyphus sarasinorum Karsch, 1892 (Araneae: Eresidae)


Animals use nests for various functions including laying eggs, raising young and gaining protection from predators. Social insect colonies provide rich microhabitats for various foreign inhabitants. Social spiders in the family Eresidae live in large, long-lasting colonies with a dense silken nest where spiders reside in complex capture webs. Social spider colonies contain several organisms apart from the host spiders, yet little is known about the foreign species and their roles. In this study, we cataloged foreign animals found in the nests and webs of the Indian social spider Stegodyphus sarasinorum Karsch, 1892 from different sites in India. We then examined the abundance and diversity of foreign spiders in adult and juvenile colonies, and the nature of interaction of foreign spiders with host S. sarasinorum spiders. We found spiders classified into nine families and insects classified into five orders and a few small vertebrate taxa associated with S. sarasinorum colonies. Adult S. sarasinorum nests and webs contained significantly more foreign spiders than juvenile colonies. However, diversity of foreign spiders did not increase with the number of host spiders. Additionally, we found that foreign spiders found inside the nests preyed on individual S. sarasinorum spiders. Our study sheds light onto the intriguing biology of nest- and web-associates of social spiders.

Web construction behavior of Deinopis cf. cylindracea (Deinopidae: Araneae) and its comparison to webs of other Deinopidae


Deinopid spiders use highly specialized webs composed of a triangular non-sticky scaffolding (NS scaffolding) containing three radii and a modified orbicular web with a rectangular shape to capture prey. Spiders actively manipulate their webs to capture prey. We describe the web construction behavior of Deinopis cf. cylindracea and compare it and the shape of the sticky silk spiral (SS spiral) of other deinopid species using images in the literature and on the Internet. The web-building behavior in D. cf. cylindracea follows the pattern previously described for other species of Deinopis MacLeay, 1839. Web construction takes approximately 15 min in D. cf. cylindracea and has two stages: NS scaffolding construction and SS spiral construction. The final structure of the SS spiral has four closely spaced capture cords, five placed further apart, three near the top of the web, and two cords on the handles, making a total of 12. Other species of Deinopis have different numbers of cords. Finally, a novel finding is that the youngest spiders do not make webs with sticky lines, but instead use a simplified web to lunge forward, using only their legs to contact prey. To our knowledge, such behavior has never been described in this or any other group.

Sexual dialogue in Pachyloides thorellii (Opiliones: Gonyleptidae): a Neotropical harvestman with much to say


Describing the signals involved in sexual interactions is crucial to understand how mating and fertilization success is achieved. We analyzed sexual interactions in the gonyleptid harvestman Pachyloides thorellii Holmberg, 1878 to test the possibility of associations between female and male behaviors. For that purpose, we recorded 21 sexual interactions of P. thorellii under laboratory conditions and performed fine scaled analyses of the videos. We found three female pre-copulatory behaviors (“Mouth parts protrusion,” “Genital operculum opening,” and “Ovipositor eversion”) that seem to be related to sexual receptivity and cooperation with mating occurrence, and four copulatory behaviors (“Bucking,” “Pulling,” “Body lowering,” and “Leg II movements”) that could be indicating to the male that further stimulation is required or that mating is about to end. We also found that males use multimodal courtship displays that include the exchange of tactile and possibly chemical signals between sexes. This study shows that courtship and copulation in P. thorellii include intense information flow between sexes and female evaluation from the beginning until the end of the sexual interaction.