Web decoration polymorphism in Argiope Audouin, 1826 (Araneidae) spiders: ontogenetic and interspecific variation

Spiders in the genus Argiope commonly include curious silk structures, termed web decorations or stabilimenta in their webs. Whilst interesting ontogenetic and interspecific variation in both the form and frequency of web decorations has been documented, to our knowledge this is the first study to compare this variation across a number of decorating species. Here we show that two sympatric species A. picta and A. aetherea construct different forms of web decorations as adults and that A. picta decorates at a higher frequency than A. aetherea. Furthermore, this difference in decoration frequency may be related to the different decoration forms (linear or cruciate) across this genus. We also show that native bees responded significantly more quickly to cruciate decorations than to linear decorations. Here we argue that consideration of the different decoration forms and the frequency at which spiders adorn their webs may help illuminate possible context‐dependent functions for these curious structures.     

Orb‐web spiders (Araneae: Araneomorphae; Orbiculariae) captured by hunting‐wasps (Hymenoptera: Sphecidae) in an area of Atlantic Forest in south‐eastern Brazil

Members of two hunting‐wasp families, Pompilidae and Sphecidae, are among the major predators of orb‐web spiders. In this study, we collected paralysed spiders from natural nests and trap‐nests provisioned by sphecids in an area of Brazilian Atlantic Forest, and compared these data with the composition of species collected by visual searching during one year. Prey preferences were analysed based on the relative abundance of spider species, their size and web characteristics. We also compiled a list of orb‐weavers captured by four sphecid genera reported in 40 other studies. A large number of prey was obtained from natural nests of Trypoxylon (Trypargilum) albonigrum in Parque Estadual Intervales, especially species of Eustala, Parawixia, and Araneus (Araneidae). Other prey, stored in trap‐nests by T. lactitarse and unidentified hunting‐wasp species, included Nephila (Tetragnathidae), Parawixia, Ocrepeira, Mecynogea, Acacesia (Araneidae), and other spider species that were less abundant. All the species that were heavily preyed upon had a relatively lower abundance in our samples of prey availability. The range of body sizes of spiders captured by Trypoxylon in our study area include the size of some abundant orb‐weavers always absent in their nests. These results indicate that factors other than abundance in the field and the spider's size influence prey selection or susceptibility to attack.     

Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae,Theridiosomatidae)

Wendilgarda sp. builds unusually simple webs attached to the surface of water. The simplest design consists of a single vertical line with sticky material near the bottom that is attached at the top to a single horizontal line and at the bottom to the water surface. The spider usually sits immobile waiting for prey as the sticky line skates erratically across the surface of the water, but some spiders actively dragged their webs back and forth across the water. The web's simplicity is apparently derived with respect to the webs of other Wendilgarda species, as spiders sometimes made more complex webs similar to typical Wendilgarda webs. The simplicity of W. sp. webs may be causally related to two other unusual traits: extreme variability in web design and construction behaviour and web manipulation behaviour; and construction of prey capture webs with sticky lines by mature males, confirmed here for the first time in a confirmed member of an orb-weaving family. Some behavioural innovations in Wendilgarda, such as the attachment of a short segment of non-sticky silk to the water surface just prior to laying each segment of sticky line, may represent blocks of behaviour that have been shifted temporally in the web construction sequence.     

Two new species of Hymenoepimecis (Hymenoptera: Ichneumonidae: Pimplinae) with notes on their spider hosts and behaviour manipulation

The wasp genera included in the Polysphincta genus-group develop exclusively as koinobiont ectoparasitoids of spiders, an unusual pattern within Hymenoptera. All known species of Hymenoepimecis attack orb-web spiders and Hymenoepimecis argyraphaga was previously described inducing a sudden modification of its host's web-building behaviour. Information on parasitoid–host interactions and even on host identities for most members of the genus-group, however, remain scarce. In this study we describe two new species of Hymenoepimecis and present information on their hosts, spiders of the genera Leucauge (Tetragnathidae) and Manogea (Araneidae). Cocoon webs of both host species are distinct from their normal webs. The modified cocoon web of Leucauge roseosignata constructed under the influence of Hymenoepimecis japi sp. nov. is very similar to the cocoon web described for Leucauge argyra. It is composed of three axes, including several radial threads each, and a hub used by the larva to attach the cocoon's suspension line. Spiral viscous threads, present in normal webs and in webs of parasitized spiders carrying larvae in the initial instars, are absent in cocoon webs. In the cocoon web of Manogea porracea the horizontal sheet is poorly structured and the cocoon is attached far from the spider's normal resting position, in an area composed of a densely tangled structure.     

Host selection by a kleptoparasitic spider

Argyrodes globosus (Keyserling, 1884) is a small kleptoparasite spider that steals prey from the web of web-building spiders. In coffee plantations in the south of Mexico it was observed to parasitize five species: Gasteracantha cancriformis (Linnaeus, 1785) and Verrucosa arenata (Walckenaer, 1841) (Araneidae), Leucauge mariana (Keyserling, 1881) and Leucauge venusta (Walckenaer, 1841) (morphologically indistinguishable species) and Leucauge argyra (White, 1841) (Tetragnathidae). G. cancriformis was more frequently parasitized than the other hosts. An analysis of web diameter for each host species indicated that for L. mariana/venusta, L. argyra and V. arenata the kleptoparasite was associated with webs of a certain size range (23-33cm diameter) although a far larger range of web sizes was available (17-50cm diameter). The average size of the web of G. cancriformis (~23cm) appeared to be close to the preferred size for the kleptoparasite and this, together with an apparent absence of host aggression, may explain the prevalence of A. globosus with this host. For the parasite, web size choice may involve a tradeoff among diverse factors including prey capture rate, ease of access to the web and aggressive behaviour by the host.     

Mating behaviour and maternal care in the tropical savanna funnel-web spider Aglaoctenus lagotis Holmberg (Araneae: Lycosidae)

Despite their abundance and diversity, Neotropical spiders have been the subject of relatively few studies of behavioural ecology. The sexual behaviour and maternal care of the spider Aglaoctenus lagotis (Lycosidae) is described here. We performed experimental manipulations to test the hypothesis that males are attracted by female cues in the web. Two predictions were tested: (a) webs used by a virgin female will attract more males than webs used by an inseminated female; (b) the main cue in the web is chemical, so webs recently used by virgin females will attract more males than those that are not recently used. Additionally, we tested the hypothesis that maternal care increases offspring survivorship. Results showed that males are attracted by recently used webs (z = 0.0015; p = 0.037; z-test) and webs of virgin females (z = 0.041; p = 0.036, z-test). Male sexual behaviour presented three different categories: court, pre-mate and mate. After the mating, the females built a cocoon that was transported adhered to the spinnerets and held by the last pair of legs. After the hatching of the eggs, the young migrated to the dorsal region of the mother's body for 5 days. During maternal care the mother eliminates a yellowish drop from its oral cavity, which is collected by the young. During the development of the young until adulthood, the offspring that have their mother present in the first stages of life have greater survival compared with those without maternal care. Our results make it possible to perform comparative analyses between a South American Lycosidae species and other species distributed worldwide.     

The effects of forest fragmentation on the population ecology and natural history of a funnel-web spider

Habitat fragmentation strongly affects the abundance, distribution, body size and population genetics of invertebrates. Urban growth in Brazil has led to severe fragmentation, especially in the Atlantic Forest and savannas. The effects of this fragmentation on the common funnel-web spider Aglaoctenus lagotis were examined in two forest fragments within the interior savanna: a smaller fragment within an urban environment and a larger fragment within a rural environment. The reproductive period occurred in October, coinciding with the beginning of the rainy season, when the species was aggregated in the two forest fragments. The smaller fragment contained a larger population, and the spiders had a larger average prosoma size and web area. The presence of a larger population in a smaller area within the urban centre may reflect a limited dispersal ability, reduced predator abundance or low interspecific competition. The larger prosoma length and web area in the smaller habitat fragment suggest greater resource availability and a higher probability of capturing prey in the urban environment. In both areas, a larger number of capture threads was positively correlated with the presence of inquiline spiders in the webs. The genetic data indicate close similarity between and within the two areas, indicating that the species has low genetic variability or that the areas studied, consistent with their proximity, have separated only recently. Most savannas and forests in midwestern Brazil have recently undergone severe fragmentation, and further studies of this nature are needed.     

The parasitoid complex and parasitoid‐induced mortality of spiders (Araneae) in a Central European woodland

The parasitoid complex of spiders was studied in three different sites of a forest and, for comparison, in open habitats in north‐western Lower Saxony (Germany). Qualitative data and, for four spider species, detailed quantitative rearing data were obtained. At least 25 parasitoids of spiders were recorded (23 species of Hymenoptera and two species of Diptera). External parasitoids of spiders were rare in the woodlands; only up to 1% of the spiders collected by hand searching and sweep netting had ectoparasitoids. During the investigation 23 parasitoid species were reared from spider egg masses, 10 of them occurring in woodlands. Two species were secondary parasitoids. Several parasitoid–host relationships were recorded for the first time. Egg masses of Floronia bucculenta were parasitized up to 5% by two species of the genus Gelis. Up to 10% of the egg masses of Linyphia hortensis were parasitized by Aclastus species. Egg masses of the spider genus Ero were parasitized by three species, causing an overall mortality of 40%. For egg masses of Agroeca spp. parasitization at some locations was up to 60%. An overview of the Central European parasitoid complex of spiders is provided.     

Biology and life history of the araneophagic assassin bug Stenolemus bituberus including a morphometric analysis of the instars (Heteroptera,Reduviidae)

Stenolemus bituberus is an araneophagic “assassin bug” (Heteroptera; Reduviidae; Emesinae) that typically is found living in spider webs. We documented the life history of S. bituberus in the field for 13 months, determining its developmental phenology and microhabitat characteristics as well as describing its mating and predatory behaviour. We also included a morphometric analysis of the instars. Our study revealed that S. bituberus is univoltine with five juvenile instars. Although S. bituberus is found in the webs of spiders from a wide range of genera, it is found most commonly in the webs of Achaearanea, Badumna, Pholcus, and Stiphidion. Multiple juveniles often were found on a single web, but adults tended to be more solitary. Stenolemus bituberus appears to have two distinct hunting strategies: “stalking”, in which they slowly approach the spider, make contact and then strike; and “luring”, in which they attract the spider within range by manipulating the silk with their legs.     

Prey-holding abilities of the nests and webs of jumping spiders (Araneae,Salticidae)

Three characteristics of the silk devices of 12 species of Salticidae and three species of spiders from conventional web-building families (Dipluridae, Eresidae and Stiphidiidae) were investigated: macrostructure; prey-holding ability (measured by escape time for five types of insects); and the structure of the silk itself, as revealed by SEM. Five types of salticid nests were recognized, and a few salticids build webs. The webs of the eresid Stegodyphus mimosarum consist of thick structural threads and fine cribellate fibres. Disparity of thread diameter, although not as extreme, was observed in the webs and nests of the other species. In the webs and nests of all species, there were threads that merely rode one over the other without forming junctions and secure ‘naked’ junctions lacking accessory fibres and ‘sleeves’. Ensheathed junctions, which had ‘sleeves’, were found only in webs of Portia (Salticidae) and Cambridgea antipodiana (Amaurobiidae). The cribellate webs of Stegodyphus mimosarum (Eresidae) had greater prey-holding ability than any other webs or nests tested, but all webs and nests were capable of detaining insects at least briefly. The distinctions between spider webs and nests and between sticky and non-sticky webs are discussed.     

New Acanthodrilus species from New Caledonia (Clitellata,Megadrili, Acanthodrilidae)

A survey to explore the earthworm fauna of New Caledonia was carried out between 14 January 2014 and 2 April 2014. Altogether, 24 earthworm species were recorded, of which eight belong to the native genus Acanthodrilus including four species new to science, Acanthodrilus barrieri, A. doanus, A. millei and A. ouenghianus spp. nov., raising the number of Acanthodrilus species in New Caledonia to 29. The 16 recorded peregrine species are distributed among five families, namely Benhamiidae (5 spp.), Eudrilidae (1 sp.), Megascolecidae (8 spp.), Moniligastridae (1 sp.) and Rhinodrilidae (1 sp.).

www.zoobank.org/urn:lsid:zoobank.org:pub:4E0A6295-A2FA-43BB-993D-BB00AFF54406     

Population dynamics of the bark-dwelling spider Eustala perfida Mello-Leitão, 1947 (Araneidae)

Population dynamics of spiders may vary according to biotic and abiotic factors. We studied the phenology of the bark-dwelling spider Eustala perfida over a two-year period and investigated how temperature, precipitation, and prey availability were associated with the population of this species. The population of E. perfida presented a well-defined fluctuation, with one reproductive cycle per year. The recruitment of spiders occurred in summer, followed by successive phenological peaks at all stages of development. The species is protogynic, and the population of adult males peaks in the cold/dry season, indicating a winter mature phenological pattern. The diet of E. perfida is composed mainly of medium-sized homopterans, complemented by small dipterans and hymenopterans. We found that the higher abundance of spiders occurred two months after the highest values of precipitation and temperature, and three months after the higher abundance of potential prey items. These results indicate that spiders require time to respond to changes in environmental conditions. The species’ natural history and the structure of the trunks in which it lives may also affect the number of individuals in a particular area and over time.     

Cirolanid isopod crustaceans from the Townsville region of Queensland,Australia, with descriptions of six new species

Summary

A wide variety of littoral and sublittoral marine habitats have been sampled in the vicinity of Townsville in N.E. Australia in order to assess the diversity of cirolanid isopods present.

Of the thirteen species represented in the collections six were previously undescribed. The species present were: Cirolana schioedtei Miers, 1884 (16m in mud/sand); C. pustulosa Hale, 1925 (mainly littoral habitats such as crevices in wooden installations); C. cranchii var. australiense Hale, 1925 (mainly littoral cryptic habitats); C. tumulosa sp. nov. (3–9 m in soft particulate substrata); C. arcicauda sp. nov. (3–10 m in soft particulate substrata); C. variguberna sp. nov. (2–18 m in soft particulate substrata); C. luticola sp. nov. (2–14 m in soft particulate substrata); Neocirolana bicrista sp. nov. (11 m in particulate substrata); Excirolana orientalis Dana, 1853 (littoral sand); Pseudolana concinna (Hale, 1925) (littoral sand); Pseudolana brevifimbria sp. nov. (littoral sand); Eurydice orientalis Hansen, 1890 (plankton and 5–11 m in soft particulate substrata); Eurydice inermis Hansen, 1890 (plankton and 2–11 m in soft particulate substrata).

The new species are described in detail and additional information is given on the other species—some of which have been poorly described in the past. In addition two closely related species, i.e. Cirolana tenuistylis Miers, 1884 and C. woodjonesi Hale, 1924 are also redescribed so as to avoid any confusion with the Townsville species.     

Population dynamics and phenology of two congeneric and sympatric lynx spiders Peucetia rubrolineata Keyserling, 1877 and Peucetia flava Keyserling, 1877 (Oxyopidae)

Numerous phenological studies on spiders belonging to the families Oxyopidae, Thomisidae, Lycosidae, Selenopidae (e.g. Selenops cocheleti) and Salticidae (e.g. Psecas chapoda and Psecas viridipurpureus) have been conducted in the neotropical region. However, studies that simultaneously compare population dynamics and age structure in populations of sympatric species are limited, especially in Oxyopidae. The population dynamics and phenology of two congeneric lynx spider (Peucetia rubrolineata and Peucetia flava) were examined in southeastern Brazil. Several characteristics of the age structure were compared between the two spider species. The variation in the total abundance of individuals and age structure and their relationship with climatic variables were similar between the two spiders. Adults of these spiders were present mainly in spring, indicating an annual reproductive cycle and a ‘stenochronous spring’ phenological pattern. The recruitment of spiders occurred in summer for P. rubrolineata and P. flava, followed by successive phenological peaks at all stages of development. Rainfall and temperature had a positive correlation to population flux in the two spider species studied. Despite the significant climatic effects observed in the Serra do Japi, the phenological pattern of the population in this study was not always repeated in other species of spiders (e.g. Selenops cocheleti).     

Diversity of Salticidae (Arachnida: Araneae) in the historical and natural reserve ‘Martín García Island’, Argentina

From Martín García Island were collected 975 jumping spiders, from five environments, using beating net and manual sampling methods. Saitis variegatus Mello-Leitão, 1941 was the most abundant (24.62%). The sandy xerophilous forest had the highest species richness (23 morphospecies) and jungle showed the greatest spider abundance (n: 384). The sandy area was the least diverse and the last in relative abundance. Salticids represented 16% of the species recorded from Argentina, and the second largest family registered. The spider fauna found could be similar to that of the Southern Brasilian region, as occurs with scorpions. Two genera and two species are new records for Argentina. In addition, three new species of jumping spiders, as well as the discovery of the unknown male and female of two species, were registered. There was no record of cosmopolitan spiders or those with a large distribution range on the Island.     

The taxonomy and biology of a new species Pontonema (Nematoda,Oncholaimidae) dominant in organically polluted sublittoral sediments around Scotland,with a review of the genus

A new species of free living marine nematode, Pontonema alaeospicula sp. nov., is a dominant member of the fauna in three organically polluted sublittoral habitats off the Scottish coast. The species is described and the genus reviewed. A schematic pictorial key to the genus is provided. Some notes on the biology of P. alaeospicula sp. nov. are given, based on initial studies of the population in situ and in laboratory culture.     

Two new termite-eating Diores species (Araneae,Zodariidae) and some observations on unique prey immobilization

Two new taxa, Diores termitophagus n. sp. and D. magicus n. sp. are described. The species have been observed to prey on termites (Hodotermes mossambicus Hagen) and are assumed to be compulsory termite-eaters. Similar prey-specialization has recently been observed in other Diores species. Termites were observed to be immobilized and die after superficial contact with the spiders; only thereafter were they bitten and eaten.     

Winter-active wolf spiders (Araneae: Lycosidae) in thermal habitats from western Romania

Shores of channels with thermal water provide an adequate microclimate for maintaining wolf spiders in activity during winter. Of the spiders collected after the winter survey of 22 thermal habitats from western Romania, 93.02% were juveniles and subadults, while the remaining individuals belonged to the following seven species: Arctosa leopardus, Pardosa amentata, Pardosa proxima, Pirata piraticus, Piratula latitans, Trochosa robusta and Trochosa ruricola. The reproductive period of some species is altered under the influence of neighbouring hot waters, as revealed by the capture of females with egg sacs and spiderlings, during winter.     

Microhabitat use and intraspecific associations in the whip spider Heterophrynus longicornis (Arachnida: Amblypygi) in forest fragments formed by the Tucuruí Dam lake,Pará, Brazil

The effect of forest fragmentation on the abundance of the whip spiders Heterophrynus longicornis (Butler 1973) in land-bridge island fragments created by the lake formed by Tucuruí Dam, Pará, Brazil, was investigated. These fragments have been isolated for at least 23 years, on small islands that range in size from 12.9 to 91.3 ha. The abundance of whip spiders was calculated in 100 m transects on eight islands, both in the edge and in the interior of the islands. There were no differences in whip spider abundance between the edge or interior of islands, but the whip spiders strongly preferred areas with greater numbers of trees, trees with a DBH between 10 to 50 cm, and trees with termite nests. Over 31% of the whip spiders were found in association with other individuals on the same tree. Individuals were found in mother–offspring associations, mating pairs, and in mixed-age sex groups.     

Coral reef tanaidacean assemblages along the SW and SE Gulf of Mexico: biodiversity,geographic distribution and community structure

The biodiversity, geographic distribution, and community parameters of the benthic tanaidaceans associated with three coral reefs along the SW and SE Gulf of Mexico were analysed. A total of 15,525 specimens were grouped in 36 species. The highest value of abundance was found in the PNSAV with 6382 tanaidaceans. The PNSAV presented 30 species, the ANPT-L 16 species, and the SABS 17 species. The species with the widest distribution were Pseudonototanais sp., Condrochelia dubia, Leptochelia forresti, Synapseudes sp., Haplopolemius propinquus, Alloleptochelia longimana, and Paradoxapseudes bermudeus. In the Veracruz System Reef, the highest abundance was recorded for Condrochelia dubia and Pseudonototanais sp. The highest value of diversity was obtained in the SABS (3.08 bits/ind in the reef Bajo Diez), and the lowest value was found in the PNSAV (0.07 bits/ind in the reef Isla de Enmedio). The highest value of abundance was found in coral rubble and macroalgae. A significant relationship between depth and specific richness was found in the three reef systems. Using cluster analysis, three groups were found in each system, mainly related to the proximity to the coast and to urban areas. This is one of the first studies to show the specific substrate and attributes of three communities of tanaidaceans along the SE–SW coast of the Gulf of Mexico.