Predation activity of two winter-active spiders (Araneae: Anyphaenidae,Philodromidae)

Anyphaena accentuata and Philodromus spp. are cold adapted and winter-active spider species. Their predation activity was investigated at constant temperatures between –4 and 30 °C. The lower temperature threshold for Anyphaena was –3.7 °C, while that of Philodromus was –1.2 °C. At 1 °C the latency to capture and prey consumption was significantly shorter in Anyphaena than in Philodromus. The capture rate increased with temperature and was maximal at 15 °C in Anyphaena and at 30 °C in Philodromus. At 30 °C, the latency to the capture was significantly shorter in Philodromus than in Anyphaena whose mortality significantly increased.     

Chromosomal characteristics and karyotype evolution of Oxyopidae spiders (Araneae, Entelegynae)

We made a cytogenetic analysis of four species of Oxyopidae and compared it with the karyotype data of all species of this family. In Hamataliwa sp, the mitotic cells showed 2n♂ = 26+X(1)X(2) and telocentric chromosomes. The 2n♂ = 28, which has been described for only one oxyopid spider, is the highest diploid number reported for this family. Peucetia species exhibited distinct karyotype characteristics, i.e., 2n♂ = 20+X(1)X(2) in P. flava and 2n♂ = 20+X in P. rubrolineata, revealing interspecific chromosome variability within this genus. However, both Peucetia species exhibited telocentric chromosomes. The most unexpected karyotype was encountered in Oxyopes salticus, which presented 2n♂ = 10+X in most individuals and a predominance of biarmed chromosomes. Additionally, one male of the sample of O. salticus was heterozygous for a centric fusion that originated the first chromosomal pair and exhibited one supernumerary chromosome in some cells. Testicular nuclei of Hamataliwa sp and O. salticus revealed NORs on autosomal pairs, after silver impregnation. The majority of Oxyopidae spiders have their karyotype differentiated by both reduction in diploid number chromosome number and change of the sex chromosome system to X type; however, certain species retain the ancestral chromosome constitution 2n = 26+X1X2. The most remarkable karyotype differentiation occurred in O. salticus studied here, which showed the lowest diploid number ever observed in Oxyopidae and the second lowest registered for Entelegynae spiders.     

Social behaviour of spitting spiders (Araneae: Scytodidae) from Singapore

The social organization of Scytodes sp., a spitting spider from Singapore, was investigated in the field and in the laboratory. The characteristics considered were colony structure, maternal care, prey capture, prey sharing, adults provisioning with prey and how feeding regime influences the level of tolerance expressed by juveniles that were living together. The characteristics of this species were compared with those of other Scytodes species that have been studied previously. Based on our findings, we conclude that in this species, social organization is 'periodic-social', with extended maternal care, this being a type of 'subsociality'. The females of Scytodes sp. wrapped their eggs in a silk egg sac and used their chelicerae to hold the eggs until they hatched. Spiderlings tended to remain in their mother's web until the fourth instar (i.e. after the third moult) but they were also highly aggressive and cannibalistic towards conspecifics after the third instar. Females carried prey to their spiderlings and either fed alongside the brood or left them to feed alone. Spiderlings also captured large prey cooperatively by spitting onto, biting and feeding on it together. The occurrence of cannibalism among her juveniles did not appear to be influenced by whether the adult female was present or not, nor did it appear to be influenced by prey abundance.     

New cave-dwelling armored spiders (Araneae,Tetrablemmidae) from Southwest China

A new genus and five new species belonging to the family Tetrablemmidae are described from caves in Southwest China, i.e., Sinammaoxycera gen. & sp. n., Singaporemma banxiaoensis sp. n., Singaporemma wulongensis sp. n., Tetrablemma ziyaoensis sp. n. andTetrablemma menglaensis sp. n. The following new combination is proposed: Sinamma sanya (Lin & Li, 2010), comb. n. ex. Shearella Lehtinen, 1981. The relationships of the Sinamma gen. n. with other genera are discussed. Diagnoses and illustrations for all new taxa are given.     

Predator-prey interactions between jumping spiders (Araneae, Salticidae) and Phokus phalangioides (Araneae, Pholcidae)

Portia is a genus of specialized web-invading salticids that use aggressive mimicry. Some other salticids leap into webs to catch spiders but do not use aggressive mimicry. Pholcus phalangioides is a web-building spider with a special defensive behaviour—called whirling—in which it swings its body around in a circle while keeping its long legs on the silk. Pholcus phalangioides is preyed on by Portia and probably other salticid spiders in nature. Interactions between P. phalangioides and 13 species of salticids were studied in the laboratory to compare how effective salticids with different styles of predation were at catching the pholcids. Four species of Portia were studied and each was more efficient at catching P. phalangioides than were the other nine salticids tested. For one species—Portia fimbriata—individuals from three different populations were studied. The Queensland P. fimbriata used aggressive mimicry more consistently and were more efficient at catching P. phalangioides than were the other species of Portia and the other populations of P. fimbriata . The salticids that were the most efficient at catching pholcids were also better able to avoid setting off whirling by the pholcids. An experiment in which pholcids were artificially induced to whirl whenever the predator was near provided additional evidence that whirling is an effective defence of pholcids against predation by salticids.     

New data on spiders (Arachnida: Araneae) of Iraq

Until recently only 33 species of spiders had been known from Iraq. New material collected in northern Iraq reveals 20 species, 13 genera and six families new to the country. One species, Pterotricha arzhantsevi sp. n. is described as new to science. Comparative figures are provided for seven species; the 54 species currently known from Iraq are listed and their occurrence in neighbouring Iran and Turkey is shown.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:4812F8A8-7A95-4D66-8E2D-CE42F73E7E91     

The phylogeny of the social Anelosimus spiders (Araneae: Theridiidae) inferred from six molecular loci and morphology

We use fragments of three nuclear genes (Histone 3, 18SrDNA, and 28SrDNA) and three mitochondrial genes (16SrDNA, ND1, and COI) totalling approximately 4.5kb, in addition to morphological data, to estimate the phylogenetic relationships among Anelosimus spiders, well known for their sociality. The analysis includes 67 individuals representing 23 of the 53 currently recognized Anelosimus species and all species groups previously recognized by morphological evidence. We analyse the data using Bayesian, maximum likelihood, and parsimony methods, considering the genes individually as well as combined (mitochondrial, nuclear, and both combined) in addition to a 'total evidence' analysis including morphology. Most of the data partitions are congruent in agreeing on several fundamental aspects of the phylogeny, and the combined molecular data yield a tree broadly similar to an existing morphological hypothesis. We argue that such congruence among data partitions is an important indicator of support that may go undetected by standard robustness estimators. Our results strongly support Anelosimus monophyly, and the monophyly of the recently revised American 'eximius lineage', although slightly altered by excluding A. pacificus. There was consistent support for the scattering of American Anelosimus species in three clades suggesting intercontinental dispersal. Several recently described species are reconstructed as monophyletic, supporting taxonomic decisions based on morphology and behaviour in this taxonomically difficult group. Corroborating previous results from morphology, the molecular data suggest that social species are scattered across the genus and thus that sociality has evolved multiple times, a significant finding for exploring the causes and consequences of social evolution in this group of organisms.     

How to catch foliage-dwelling spiders (Araneae) in maize fields and their margins: a comparison of two sampling methods

The foliage‐dwelling spider fauna was collected in maize fields and on stinging nettles in adjacent margins in Bavaria, South Germany. Two different sampling methods were evaluated: drop cloth sampling and suction sampling. The overall catch was dominated by juvenile spiders, web‐building spiders, and spiders of the families Theridiidae, Linyphiidae, Tetragnathidae and Araneidae (in decreasing order). Field margins harboured more species than maize fields, whereas the total spider abundance was higher in the maize crop. Web‐building spiders such as Theridiidae and Linyphiidae were prominent in maize by individual numbers. Suction sampling with a small suction device proved to be a more efficient and consistent sampling method for foliage‐dwelling spiders than drop cloth sampling. Density and species richness of foliage‐dwelling spiders in maize was shown to be fairly high, implying that spiders of higher strata may play a more important role in biological control than suspected up to now.     

Colony size and parasitoid load in two species of colonial Metepeira spiders from Mexico (Araneae: Araneidae)

Summary While a number of advantages may result from group living, it may also lead to increased levels of attack by parasites because groups may be easier to find. This leads to the prediction that levels of parasitism should increase with colony size. We test this prediction by comparing colony size and parasitoid load for two species of colonial orb-weaving spiders from Mexico, Metepeira (undesc. sp., tentatively named atascadero) and Metepeira incrassata, which exhibit contrasting levels of social organization and utilize different habitats. For M. atascadero, which occurs solitarily or in small groups in desert/mesquite grassland habitat, rates of egg-sac parasitism fluctuate widely from year to year, and are closely tied to spider egg output. There is no relationship between colony size and rate of parasitism. For colonial M. incrassata, which occur in tropical rain forest/agricultural habitat, rates of parasitism are relatively constant from year to year. However, there is a positive relationship between colony size and rate of parasitism in this species. These differences are discussed with regard to the stability of the two habitats, prey availability, and the foraging behavior of the respective parasitoids.     

Competition between introduced and native spiders (Araneae: Linyphiidae)

The European sheet-web spider Linyphia triangularis (Araneae: Linyphiidae) has become established in Maine, where it often reaches very high densities. Two lines of evidence from previous work suggest that L. triangularis affects populations of the native linyphiid spider Frontinella communis. First, F. communis individuals are relatively scarce in both forest and coastal habitat where L. triangularis is common, but more common where L. triangularis is at low density. Second, in field experiments, F. communis species are less likely to settle in experimental plots when L. triangularis is present, and F. communis disappears from study plots when L. triangularis is introduced. Here we test two mechanisms that may underlie these patterns. First, we tested whether L. triangularis invades and usurps the webs of F. communis. When spiders were released onto webs of heterospecifics, L. triangularis was more likely to take over or share webs of F. communis than the reverse. We also observed natural takeovers of F. communis webs. Second, we explored the hypothesis that L. triangularis reduces prey availability for native species. We sampled flying prey in areas with L. triangularis and those where it had been removed, and found no effect of spider presence on measured prey density. We also found no effect of prey supplementation on web tenacity in F. communis, suggesting that F. communis movements are not highly dependent on prey availability. We conclude that web takeover is likely more important than prey reduction in driving negative effects of L. triangularis on F. communis.     

Two Trichosporon species isolated from Central-European mygalomorph spiders (Araneae: Mygalomorphae)

Trichosporon (Dikarya: Basidiomycota) is a genus of anamorphic yeasts typically associated with soil and water, although many species are causative agents of diseases in animals and man. Here we provide the first compelling evidence that spiders can be occasionally colonized by at least two Trichosporon species. Trichosporon dulcitum (Berkhout) Weijman 1979 was isolated from the exoskeleton of purse-web spider Atypus piceus, while Trichosporon porosum (Stautz) Middelhoven, Scorzetti & Fell 2001 was isolated from the exoskeleton of purse-web spider Atypus affinis. Both of the species were identified based on DNA sequence analysis of the host specimens displaying macroscopic signs of the superficial white mycosis on their exoskeleton. Only two specimens with macroscopic signs of superficial yeast growth were identified among the 125 individuals of A. affinis, A. piceus and Atypus muralis examined that were collected at various sites throughout the Czech Republic. The consistent burrow microclimate, uninterrupted occupancy of the single burrow for several subsequent years, and presence of prey remnants in the burrow below the purse-web may play a role in the course of infection of the mygalomorphs examined. The phylogenetic relationships of Trichosporon species are analyzed, concluding that association with invertebrates clusters predominantly among four groups of closely related species in independent Trichosporon clades.     

Some comments on the hydrostatic system of spiders (Chelicerata,Araneae)

An anatomical study of five spider types has shown that the musculi laterales of the prosoma, together with the subcuticular muscle sheet of the opisthosoma, may be jointly responsible for generating the internal hydrostatic pressures which control the leg extension mechanism.     

New cave-dwelling spiders of the family Dictynidae (Arachnida: Araneae) from Guangxi and Guizhou,China

Twenty-four new spider species of the family Dictynidae from caves of Guangxi and Guizhou in southern China are described,accompanied by line drawings and photomicroscopy images.Fifteen of them belong to Brommella Tullgren,1948:B.baiseensis Li,sp.nov.,B.casseabri Li,sp.nov.,B.chongzuoensis Li,sp.nov.,B.dolabrata Li,sp.nov.,B.funaria Li,sp.nov.,B.josephkohi Li,sp.nov.,B.linyuchengi Li,sp.nov.,B.renguodongi Li,sp.nov.,B.resima Li,sp.nov.,B.sejuncta Li,sp.nov.,B.spirula Li,sp.nov.,B.tongyanfengi Li,sp.nov.,B.wangfengcheni Li,sp.nov.,B.xinganensis Li,sp.nov.and B.yizhouensis Li,sp.nov.;eight to Cicurina Menge,1871:C.avicularia Li,sp.nov.,C.damaoensis Li,sp.nov.,C.dong Li,sp.nov.,C.kailiensis Li,sp.nov.,C.majiangensis Li,sp.nov.,C.parallela Li,sp.nov.,C.wusanani Li,sp.nov.,and C.zhazuweii Li,sp.nov.;one to Lathys Simon,1884:L.inaffecta Li,sp.nov.Types of all new species are deposited in the Institute of Zoology,Chinese Academy of Sciences in Beijing (IZCAS).     

Two new species of litter-dwelling Metagonia spiders (Araneae, Pholcidae) document both rapid and slow genital evolution

The observation that genitalia, rather than other characters, are useful in distinguishing species has resulted in the statement that genitalia evolve relatively rapidly. In this paper we claim that relatively rapid evolution of genitalia may often be restricted to the shapes, numbers, and sizes of individual structures. In contrast, the more basic pattern, including the presence or absence of structures and their interrelationships (the bauplan), does not seem to evolve more rapidly than other (nongenital) aspects of morphology. We document this idea by contrasting two litter‐dwelling pholcid species, Metagonia petropolis sp. n. and M. paranapiacaba sp. n., with their mostly leaf‐dwelling congeners. Significant differences occur with regard to nongenital aspects of morphology as well as shapes of individual genital structures, but the bauplan of their genitalia is basically the same.     

Two spiders in subfamily Mynogleninae (Araneae: Linyphiidae) from the Falkland Islands, South Atlantic

Two new taxa, Falklandoglenes spinosa gen. nov. and sp. nov. and Beauchenia striata gen. nov. and sp. nov. , are described from Beauchêne Island, the most remote island in the Falkland Islands archipelago. Both species are in subfamily Mynogleninae, previously thought to be confined to Central Africa and to New Zealand and its neighbouring subantarctic islands. Both species show intermediate characters between the Mynogleninae and the remainder of the Linyphiidae, and hence they throw some light on the phylogeny of this large, complex, world–wide family of spiders.     

A survey of linyphiid spiders from Xishuangbanna,Yunnan Province,China (Araneae,Linyphiidae)

Eight new genera and 30 new species are described: Cirrosus gen. n. (type species Cirrosus atrocaudatus sp. n. (♂♀)), Conglin gen. n. (type species Conglin personatus sp. n. (♀)), Curtimeticus gen. n. (type species Curtimeticus nebulosus sp. n. (♂)), Gladiata gen. n. (type species Gladiata fengli sp. n. (♂)), Glebala gen. n. (type species Glebala aspera sp. n. (♂)), Glomerosus gen. n. (type species Glomerosus lateralis sp. n. (♂)), Smerasia gen. n. (type species Smerasia obscurus sp. n. (♂♀)), Vittatus gen. n. (type species Vittatus fencha sp. n. (♂♀)); Batueta cuspidata sp. n. (♂♀), Capsulia laciniosa sp. n. (♂), Dactylopisthes separatus sp. n. (♀), Gongylidiellum bracteatum sp. n. (♀), Houshenzinus xiaolongha sp. n. (♂♀), Laogone bai sp. n. (♂), Laogone lunata sp. n. (♂♀), Maro bulbosus sp. n. (♀), Nasoonaria circinata sp. n. (♂♀), Neriene circifolia sp. n. (♂♀), Oedothorax biantu sp. n. (♀), Oilinyphia hengji sp. n. (♂♀), Paikiniana furcata sp. n. (♂♀), Parameioneta bishou sp. n. (♂♀), Parameioneta multifida sp. n. (♂♀), Parameioneta tricolorata sp. n. (♂♀), Tapinopa undata sp. n. (♂), Theoa bidentata sp. n. (♂♀), Theoa vesica sp. n. (♂♀), Vittatus bian sp. n. (♂♀), Vittatus latus sp. n. (♂♀), Vittatus pan sp. n. (♂♀). The male of Kaestneria bicultrata Chen & Yin, 2000 and the females of Asiagone perforata Tanasevitch, 2014 and Batueta similis Wunderlich & Song, 1995 are described for the first time; photos of Bathyphantes paracymbialis Tanasevitch, 2014 are provided.