Oldest true orb-weaving spider (Araneae: Araneidae)

The aerial orb web woven by spiders of the family Araneidae typifies these organisms to laypersons and scientists alike. Here we describe the oldest fossil species of this family, which is preserved in amber from Alava, Spain and represents the first record of Araneidae from the Lower Cretaceous. The fossils provide direct evidence that all three major orb web weaving families: Araneidae, Tetragnathidae and Uloboridae had evolved by this time, confirming the antiquity of the use of this remarkable structure as a prey capture strategy by spiders. Given the complex and stereotyped movements that all orb weavers use to construct their webs, there is little question regarding their common origin, which must have occurred in the Jurassic or earlier. Thus, various forms of this formidable prey capture mechanism were already in place by the time of the explosive Cretaceous co-radiation of angiosperms and their flying insect pollinators. This permitted a similar co-radiation of spider predators with their flying insect prey, presumably without the need for a 'catch-up lag phase' for the spiders.     

Phylogeny of the orb-weaving spider family Araneidae (Araneae: Araneoidea)

We present a new phylogeny of the spider family Araneidae based on five genes (28S, 18S, COI, H3 and 16S) for 158 taxa, identified and mainly sequenced by us. This includes 25 outgroups and 133 araneid ingroups representing the subfamilies Zygiellinae Simon, 1929, Nephilinae Simon, 1894, and the typical araneids, here informally named the “ARA Clade”. The araneid genera analysed here include roughly 90% of all currently named araneid species. The ARA Clade is the primary focus of this analysis. In taxonomic terms, outgroups comprise 22 genera and 11 families, and the ingroup comprises three Zygiellinae and four Nephilinae genera, and 85 ARA Clade genera (ten new). Within the ARA Clade, we recognize ten informal groups that contain at least three genera each and are supported under Bayesian posterior probabilities (≥ 0.95): “Caerostrines” (Caerostris, Gnolus and Testudinaria), “Micrathenines” (Acacesia, Micrathena, Ocrepeira, Scoloderus and Verrucosa), “Eriophorines” (Acanthepeira, Alpaida, Eriophora, Parawixia and Wagneriana), “Backobourkiines” (Acroaspis, Backobourkia, Carepalxis, Novakiella, Parawixia, Plebs, Singa and three new genera), “Argiopines” (Arachnura, Acusilas, Argiope, Cyrtophora, Gea, Lariniaria and Mecynogea), “Cyrtarachnines” (Aranoethra, Cyrtarachne, Paraplectana, Pasilobus and Poecilopachys), “Mastophorines” (Celaenia, Exechocentrus and Mastophora,), “Nuctenines” (Larinia, Larinioides and Nuctenea), “Zealaraneines” (Colaranea, Cryptaranea, Paralarinia, Zealaranea and two new genera) and “Gasteracanthines” (Augusta, Acrosomoides, Austracantha, Gasteracantha, Isoxya, Macracantha, Madacantha, Parmatergus and Thelacantha). Few of these groups are currently corroborated by morphology, behaviour, natural history or biogeography. We also include the large genus Araneus, along with Aculepeira, Agalenatea, Anepsion, Araniella, Cercidia, Chorizopes, Cyclosa, Dolophones, Eriovixia, Eustala, Gibbaranea, Hingstepeira, Hypognatha, Kaira, Larinia, Mangora, Metazygia, Metepeira, Neoscona, Paraplectanoides, Perilla, Poltys, Pycnacantha, Spilasma and Telaprocera, but the placement of these genera was generally ambiguous, except for Paraplectanoides, which is strongly supported as sister to traditional Nephilinae. Araneus, Argiope, Eriophora and Larinia are polyphyletic, Araneus implying nine new taxa of genus rank, and Eriophora and Larinia two each. In Araneus and Eriophora, polyphyly was usually due to north temperate generic concepts being used as dumping grounds for species from southern hemisphere regions, e.g. South-East Asia, Australia or New Zealand. Although Araneidae is one of the better studied spider families, too little natural history and/or morphological data are available across these terminals to draw any strong evolutionary conclusions. However, the classical orb web is reconstructed as plesiomorphic for Araneidae, with a single loss in “cyrtarachnines”–“mastophorines”. Web decorations (collectively known as stabilimenta) evolved perhaps five times. Sexual dimorphism generally results from female body size increase with few exceptions; dimorphic taxa are not monophyletic and revert to monomorphism in a few cases.     

A phylogenetic analysis of the orb-weaving spider family Araneidae (Arachnida, Araneae)

We present the first cladistic analysis focused at the tribal and subfamily level of the orb-weaving spider family Araneidae. The data matrix of 82 characters scored for 57 arancid genera of 6 subfamilies and 19 tribes (and 13 genera from 8 outgroup families) resulted in 16 slightly different, most parsimonious trees. Successive weighting corroborated 62 of the 66 informative nodes on these cladograms; one is recommended as the 'working' araneid phylogcny. The sister group of Araneidae is all other Araneoidea. Araneidae comprises two major clades: the subfamily Araneinae, and the 'argiopoid' clade, which includes all other subfamilies and most tribes (((Gasteracanthinae, Caerostreae), (((Micratheninae, Xylcthreae), Eruyosaccus ), (Eurycorminae, Arciinae)), Cyrlarachninae), ((Argiopinae, Cyrtophorinae), Arachnureae)). Cyrtarachneae and Mastophoreae are united in a new subfamily, Cyr-tarachninae. The spiny orb-weavers alone (Gasteracanthinae and Micratheninae) are not monophyletic. The mimetid subfamily Arciinae and the 'tetragnathid' genus Zygiella are araneids, but .Nephila (and other tetragnathids) are not. On the preferred tree, web decorations (stabilimenta) evolved 9 times within 15 genera, and were lost once. The use of silk to subdue prey evolved once in cribellate and four times in ecribillate orb weavers. Sexual size dimorphism evolved once in nephilines, twice in araneids, and reverted to monomorphism five times. Evolution in other genitalic and somatic characters is also assessed; behavioral and spinneret features arc most consistent (male genitalia, leg and prosomal features least consistent) on the phylogeny.     

On the spider genus Amaurobius (Araneae, Amaurobiidae) in India and Nepal

A new species, Amaurobius koponenisp. n., is described from Himachal Pradesh on the basis of a male specimen. A key to all five genera of Amaurobiidae that occur in Asia is provided. Four species from India and Nepal incorrectly assigned to Amaurobius are transferred to three genera of Titanoecidae: Anuvinda milloti (Hubert, 1973), comb. n., Pandava andhraca (Patel & Reddy, 1990), comb. n., Pandava nathabhaii (Patel & Patel, 1975), comb. n., and Titanoeca sharmai (Bastawade, 2008), comb. n.     

Previous experience and site tenacity in the orb spider Nephila (Araneae,Araneidae)

Summary The tenacity of the orb spider Nephila clavipes to a web site was studied in the laboratory. No differences were found between the giving-up-times and the site tenacity of spiders reared in the laboratory or those caught in the field, nor between spiders raised under a poor or a richt diet. The animals left sites at random and seemed to ignore experiences gained at previous sites.     

A new combination expands the range of the African araneid spider Singafrotypa (Araneae, Araneidae)

Study of the syntype of Larinioides subinermis, a species known from Ethiopia only, revealed that it actually belongs to Singafrotypa Benoit, 1962. We redescribe Singafrotypa subinermis (Caporiacco, 1940), comb. n., and provide a key to females of four species belonging to Singafrotypa. A distribution map for all species is provided.     

Function of bright coloration in the wasp spider Argiope bruennichi (Araneae: Araneidae)

There are two major competing explanations for the counter-intuitive presence of bright coloration in certain orb-web spiders. Bright coloration could lure insect prey to the web vicinity, increasing the spider's foraging success. Alternatively, the markings could function as disruptive camouflage, making it difficult for the insect prey to distinguish spiders from background colour variation. We measured the prey capture rates of wasp spiders, Argiope bruennichi, that were blacked out, shielded from view using a leaf fragment, or left naturally coloured. Naturally coloured spiders caught over twice the number of prey as did either blacked-out or leaf-shielded spiders, and almost three times as many orthopteran prey. Spectrophotometer measurements suggest that the bright yellow bands on the spider's abdomen are visible to insect prey, but not the banding on the legs, which could disguise the spider's outline. Thus, our results provide strong support for the hypothesis that bright coloration in the wasp spider acts as a visual lure for insect prey and weak support for the hypothesis that the arrangement of the banding pattern across the spider's body disguises the presence of the spider on the web.     

On the spider genus Arboricaria with the description of a new species (Araneae,Gnaphosidae)

The spider genus Arboricaria Bosmans, 2000 is redefined and an updated diagnosis given. The differences between Arboricaria and Micaria Westring, 1851 are discussed in detail. A key to all five species of the genus is provided. One new species, Arboricaria zonsteini sp. n. (♂♀), is described based on specimens from Kyrgyzstan and Azerbaijan. One new synonym is proposed: Arboricaria koeni Bosmans in Bosmans & Blick, 2000, syn. n. is assigned to Arboricaria sociabilis Kulczyński in Chyzer & Kulczyński, 1897. Data on the distribution of Arboricaria in Russia and adjacent countries are presented with references to the papers on local spider faunas.     

Phylogenetic relationships of the Neotropical spider genus Itatiaya (Araneae)

Polotow, D. & Brescovit, A. D. (2010). Phylogenetic relationships of the Neotropical spider genus Itatiaya (Araneae). —Zoologica Scripta, 40, 187–193. A cladistic analysis using parsimony under equal weights is applied to test the phylogenetic relationships of Itatiaya Mello‐Leitão, previously described in Ctenidae. The data matrix comprised 25 taxa scored for a total of 47 characters. The cladistic analysis yielded two equally parsimonious trees of 124 steps. The consensus of the two most parsimonious trees is used to discuss the phylogenetic relationships and justify taxonomic modifications. The results indicate that this genus is a representative of Zoropsidae, which is newly recorded from the Neotropical region. The monophyly of Itatiaya is supported by three non‐ambiguous synapomorphies and three homoplastic synapomorphies. A new diagnosis is provided for Itatiaya. Itatiaya pucupucu is placed as sister species to the remaining species of the genus. A polytomic clade composed of Itatiaya modesta, Itatiaya iuba, Itatiaya apipema and the clade formed by Itatiaya tacamby + Itatiaya pykyyra is supported by the presence of modified cylindrical gland spigots. Additionally, the male of I. pykyyra Polotow & Brescovit is described for the first time.     

On the spider genus Liphistius (Araneae: Mesothelae) in Thailand and Burma

Seven of the ten Liphistius species already known from Thailand and Burma are characterized; three new species, L. lannaianus sp.n., L. marginatus sp.n., L. thaleban sp.n., and the males of L. lordac Platnick & Scdgwiek and L. niphanae Ono are described. Taxonomy and relationships are discussed; considerable variation in female internal genitalia is shown. Notes are given on natural history, distribution, burrow structure, phenology and behaviour.     

Spiderling sex ratio and maternal investment in the bolas spider Mastophora cornigera (Araneae,Araneidae)

Male Mastophora cornigera exit egg sacs as adults, which allowed us to determine spiderling sex ratios and patterns of maternal investment in this species. We collected 15 egg sacs produced by seven mothers, which yielded 1945 emergent spiderlings which were sexed, 1850 of which were weighed. Two emergent broods were significantly male and female biased and were unaffected by pre-emergence mortality. The weights of male and female spiderlings differed in eight broods, with males and females being heavier in four cases each. Five of these broods were derived from multiple egg sac sets produced by one mother, and in each case, the total mean male and female spiderling weights for all broods in a set were biased in the same direction as the biased brood(s) within that set. Mean emergent spiderling weight was independent of brood size and sex ratio for both males and females. Despite such independence, sex allocation in M. cornigera can favor sons, daughters, or both equally, and by numbers, by weight, or both at once. The proximate mechanisms and adaptive significance of such variability is unknown. We also review evidence for gender-biased allocations in arachnid offspring and suggested mechanisms for their applicability to M. cornigera.     

Cave adaptation in the spider genus Anthrobia (Araneae, Linyphiidae, Erigoninae)

The genus Anthrobia Tellkampf, 1844 is revised and expanded to include two epigean species, Anthrobia acuminata ( Emerton, 1913 ) comb. nov., and A. whiteleyae sp. nov., and two troglobites, the type species A. monmouthia Tellkampf, 1844 , and A. coylei sp. nov. The female of A. acuminata is described for the first time. All four Anthrobia species were added to a phylogenetic analysis of erigonine genera. Analysis of this matrix results in a single most parsimonious tree (length = 915, CI = 0.23, RI = 0.58; uninformative characters excluded: length = 911, CI = 0.23), which places Anthrobia sister to Diplocentria Hull, 1911. Troglobitic Anthrobia and epigean Anthrobia are both monophyletic. In comparison to the epigean species, troglobitic Anthrobia exhibit the following putative adaptations to cave life: loss of eyes, elongation of the legs, and reduction of the tracheal system. The reliability of phylogenetic results indicating monophyly of cave Anthrobia are discussed in light of the fact that potentially cave adaptive synapomorphies support this relationship.     

Anti-predator defences of Argiope appensa (Araneae, Araneidae), a tropical orb-weaving spider

Anti-predator defence behaviour of Argiope appensa (Fuesslin) (Araneae, Araneidae) was studied in the laboratory. The most frequent response of adults and large juveniles of A. appensa to disturbance was pumping, a behaviour during which this web-building spider moved its body rapidly up and down with its legs remaining on the silk. When disturbed, small juveniles differed from adult females and larger juveniles by often dropping from the web instead of pumping. Argiope appensa sometimes put its web betweeen itself and stimuli from potential predators by shuttling from one side of the hub to the other. Argiope appensa occasionally tugged on the web but this behaviour appeared to be primarily a component of prey-catching sequences instead of defence. Experiments were carried out to determine the types of stimuli that elicited pumping. Lightly touching the spider or its web, forcefully hitting the web, and air movement elicited pumping but there was no evidence that chemical stimuli from potential predators were important.     

Heterozygosity and fitness in a California population of the labyrinth spider Metepeira ventura (Araneae, Araneidae)

Abstract. The relationship between individual heterozygosity and characteristics likely to be associated with fitness was investigated in the labyrinth spider Metepeira ventura . Adult females and their egg sacs were collected at a coastal site in southern California, and three measures of bodily condition (carapace width, weight, residual index) and six measures of reproductive output (number of egg sacs, variation in egg number among sacs [coefficient of variation], total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were determined for each spider. The sample was polymorphic at three allozyme loci that were in Hardy–Weinberg equilibrium, and individual females were heterozygous at up to two of the three loci, forming three heterozygosity classes (0, 1, and 2). None of the bodily condition measures were significantly related to the number of heterozygous loci, while four of the reproductive output estimators (total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were significantly influenced by heterozygosity. In each significant case, values for class 2 females were less than those for class 0 and 1 females, whose values were usually more similar. Thus, while female bodily condition was comparable among classes, the most heterozygous females produced fewer total eggs and eggs per sac than their less heterozygous peers. The fact that females of M. ventura engage in a reproductive investment-number trade-off suggests that high-variability and low-variability females may be pursuing distinct reproductive strategies in the wild, with more heterozygous females being K -selected (smaller clutches, heavier eggs) and more homozygous females being r -selected (larger clutches, lighter eggs). Further investigation will be needed to assess more fully the fitness value of heterozygosity in M. ventura .     

Organization of the spinnerets and spigots in the orb web spider,Argiope bruennichi (Araneae: Araneidae)

Although the basic taxonomic characteristics usually remain unchanged, some spinning apparatuses undergo consistent adaptive variations. As the presence of additional protuberances known as nubbins and tartipores have caused disagreements regarding some Araneidae spiders, more detailed definitions on the cuticular structures have recently been proposed. Reflecting this definition, microstructural organization of silk spinning apparatuses in the orb web spider Argiope bruennichi were reconsidered using field emission scanning electron microscopy. Among the seven kinds of functional spigots in females, it was revealed that two types (major ampullates and pyrifoms) are located on anterior spinnerets and another five types are distributed on median (minor ampullates, tubuliforms and aciniforms) or posterior (tubuliforms, flagelliforms, aggregates and aciniforms) spinnerets, respectively. In addition to functional spigots, cuticular remnants of the nubbins and the tartipores were found on the spinning fields, but the number of tartipores on each spinneret varied among individuals based on maturity. Nevertheless, three kinds of cuticular protuberances of ampullate silk glands were clearly visible at both the anterior and median spinnerets.     

The spider genus Enoplognatha (Araneae: Theridiidae) in Israel

Israeli theridiid spiders of the genus Enoplognatha are revised. Five species, four of them new, each represented by the two sexes, are recognized, and their affinities with similar species from adjacent regions are discussed. All species previously described from this region have been re-examined. The occurrence of E. mandibularis , formerly reported from Israel, has been confirmed, while the record of E. ovata has proved erroneous. A key to the species is provided.     

Genital damage in the orb-web spider Argiope bruennichi (Araneae: Araneidae) increases paternity success

The morphology of male genitalia often suggests functions besidessperm transfer that may have evolved under natural or sexualselection. In several species of sexually cannibalistic spiders,males damage their paired genitalia during mating, limitingthem to one copulation per pedipalp. Using a triple-mating experiment,we tested if genital damage in the orb-web spider Argiope bruennichiincreases male fitness either through facilitating his escapefrom an aggressive female or by obstructing the female's inseminationducts against future copulation attempts from other males. Wefound no survival advantage for males damaging their pedipalps;however, copulations into a previously used insemination ductwere significantly shorter when the previous male had left partsof his genitalia inside the insemination duct. Because copulationduration determines paternity in this species, our result suggeststhat male genital damage in A. bruennichi is sexually selected.By breaking off parts of their intromittent organs inside avirgin female, males can reduce sperm competition and therebyincrease their paternity success.     

Assessment of rampant genitalic variation in the spider genus Homalonychus (Araneae, Homalonychidae)

Abstract. Animal genitalia are often complex and thought to vary little within species but differ between closely related species making them useful as primary characters in species diagnosis. Spiders are no exception, with nearly all of the 40,462 (at the time of this writing) described species differentiated by genitalic characteristics. However, in some cases, the genitalia of putative species are not uniform, but rather vary within species. When intraspecific variation overlaps interspecific variation, it can be difficult (if not impossible) to place a name on a specimen. The quantification of shape variation in genitalia has not often been attempted, probably because until recently it was not a methodologically and computationally simple process. In the two currently recognized species of the spider genus Homalonychus , genitalic variation is rampant in both male and female structures, with some parts of the genitalia (e.g., the retrolateral tibial apophysis) differing in each specimen examined. In this study, geometric morphometric analysis employing landmark data is used to quantify both intra- and interspecific variation in this genus. The large amount of variation is condensed into two or three groups depending on the structures examined, and these groups correspond to either the two species or to previously established mitochondrial DNA clades within one of the species. The results also show that analyses of female structures do not separate the groups as readily as the analyses of the male structures. The large amount of variation present in some structures is not correlated with geography or population genetic structure.