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This study revises the status of knowledge of the spider fauna of the Society Islands. Until recently, the literature on the spider fauna in these islands has suggested that the genus Tetragnatha in particular is noticeable for its poor representation in comparison with the large radiation in the Hawaiian Islands. Expeditions were conducted to determine whether this genus is indeed poorly represented in the islands as the literature would suggest. The results indicate that the islands actually have a number of endemic Tetragnatha, although there is no noticeable adaptive radiation as is seen in the Hawaiian Islands. Results of field expeditions in 1999–2000 and studies on historical collections have shown that: (1) Reports of the cosmotropical species T. mandibulata in the Society Islands are probably not valid; these were misidentifications for either T. macilenta or T. nitens. (2) Tetragnatha huahinensis is a synonym of T. macilenta. (3) There are three new species of Tetragnatha, all of which are described here and appear to be endemic to middle and high elevations of the Society Islands (from Tahiti, Moorea and Raiatea). In total, there are six species of Tetragnatha in the Society Islands: in addition to the three endemic species there is one possibly indigenous (T. macilenta), and two that may be of more recent introduction (T. nitens and T. maxillosa).
The taxonomic status of all species of SantineziaRoewer 1923 is defined, and a catalogue is provided. Santinezia lucifer, S. gracilis, S. onorei (all from Ecuador), S. furva (from Colombia and Venezuela) and S. hermosa (from Peru) are newly described. Santinezia biordiGonzález-Sponga 1991 is newly considered as a junior subjective synonym of S. serratotibialisRoewer 1932. Santinezia albilineataRoewer 1932, Goniosoma pavaniMuñoz-Cuevas 1972, S. benedictoiSoares & Avram 1981, S. decuiAvram 1987, S. orghidaniAvram 1987 and S. francourbaniAvram 1987 are newly considered as junior subjective synonyms of Inezia curvipesRoewer 1916. NiebliaRoewer 1925, ChondrocranausRoewer 1932, MacuchicolaMello-Leitão 1943 and CarvalholeptesH. Soares 1970 are newly considered as junior subjective synonyms of Santinezia. Nieblia camposiMello-Leitão 1942 is transferred to SpinicranausRoewer 1913. Santinezia albimedialisGoodnight & Goodnight 1943 is transferred to PhareicranausRoewer 1913. Nieblia magnaRoewer 1932 is transferred to NeocranausRoewer 1913. Santinezia micheneriGoodnight & Goodnight 1947 is newly considered as a junior subjective synonym of Phareicranaus ornatusRoewer 1932. A character survey is done including newly discovered characters of genital morphology, patterns of colored marks of dorsal scutum and armature of male leg IV. A phylogenetic analysis of the species of the genus for which males are known is provided allowing the definition of three new species groups. Comparative descrip
The means by which female wolf spiders attach an egg sac to their spinnerets was investigated using scanning electron microscopy. In four Pardosa species, we observed that silk fibers emerging from ampullate gland spigots had been affixed to the surface of the egg sac. More specifically, primary (1°) and secondary (2°) major ampullate (MaA) glands and 1° and 2° minor ampullate (MiA) glands all contributed fibers for this purpose. The diameters of the 2° MaA and 2° MiA fibers were greater than those of the 1° MaA and 1° MiA fibers and, correspondingly, the widths of the 2° ampullate spigots were clearly greater than those of the 1° ampullate spigots. Larger 2° ampullate spigots were also observed in adult females of species from three other lycosid genera. Thus, 2° ampullate glands, which in araneoids function only in juveniles during proecdysis, are not only functional in adult female lycosids (and adult females of several other families), but they appear to play a greater role than the 1° ampullate glands in egg sac attachment. Observations made on the 1° and 2° ampullate spigots of adult females from species belonging to several other families are also presented. Cuticular structures referred to as nubbins and tartipores are present in some spinning fields on spinnerets. A proposal is made for defining these terms by a criterion, namely their different origins, which differs from that applied previously.
Terrestrial arthropod surveys and inventories frequently suffer from undersampling bias; common species are over-represented and rare species may be missed entirely. This study compared a rapid (3 days) and intense inventory of spiders from one hectare of a mature beech forest (Fagus sylvaticus) in Hestehaven, Denmark, comprising 8,710 adult spiders of 66 species to a previous, much more thorough, bi-weekly survey of two years duration from the same site that comprised 42,273 spiders (adult and juvenile) of 141 species. Non-parametric species richness estimators were used to assess the degree of undersampling bias in various data partitions. The current study used five experienced, four novice collectors, and five semi-quantitative collecting methods. Method and time of day strongly affected numbers of species and adults per sample. Collector experience affected numbers of species but not numbers of adults per sample. Despite the intensive collecting, number of adults per sample did not decrease over the course of the study. At the end of the sampling, 31 species were still rare in the sample (singletons or doubletons). Non-parametric richness estimators suggest that the actual richness of adult spiders in the study plot at this time of year and susceptible to the methods used was about 80 species. Species turnover between the two surveys (ca 23 years) was remarkably small: the two lists were 92% identical. The base-line study suggests that the rarity of 12 of the 31 rare species was artifactual (10 due to phenology, one to method, another to spatial edge effects). The rarity of the remainder is unexplained and by default is interpreted as undersampling bias.
It has been suggested by several authorities that at least one species of spider of the genus Theotima, family Ochyroceratidae, occurring in tropical regions in South Africa, the Caribbean and Asia may be parthenogenetic. Theotima minutissimus is particularly abundant in the tropical rainforest leaf litter on El Yunque, Puerto Rico. While many hundreds of specimens have been collected over many years, none has been a male. To examine the possibility that this small species, ± 0.9 mm body length, is parthenogenetic, live specimens were collected and maintained in the laboratory. A second generation spiderling, raised separately, produced viable progeny.
Within a species, physiological tolerances and thermoregulatory behaviors may vary among ontogenetic stages or between sexes. Such different tolerances can strongly affect the ecology and life history of a species. In a laboratory study, we tested the hypothesis that Pirata sedentarius Montgomery 1904 is differentially susceptible to thermal/desiccation stress by size and sex. As predicted, male adults were more susceptible to thermal/desiccation stress than females. Unexpectedly, however, juvenile spiders survived longer under thermal/desiccation stress than adults. Furthermore, female adults without egg sacs displayed a trend toward higher thermal/desiccation tolerance than females carrying egg sacs. These results suggest that for P. sedentarius, microhabitat preferences and/or thermoregulatory behaviors may change over the course of development, and may vary between sexes and between females with and without egg sacs.
Wolf spiders in the genus Pirata are common, often locally abundant, inhabitants of many moist or mesic habitats. However, relatively little is known about the ecology or life history of these spiders. Here we present data collected during 2000–2001 on female size, offspring size and clutch size for two populations (Ball Gulf, Hardscrabble Creek) of Pirata sedentarius from western New York. In both populations, mean offspring size was less variable than was female size, clutch size or total clutch mass. At Ball Gulf, 67% of females produced two egg sacs and 48% produced three sacs. Clutch size declined across the egg sac sequence for all females. Female size, measured as cephalothorax length, was uncorrelated with mean offspring size in all cases. However, larger females produced larger and heavier clutches during 2001 for both populations; female size was uncorrelated with these variables during 2000 at Hardscrabble Creek. Larger clutches from both populations contained more offspring, and larger clutches contained smaller offspring at Hardscrabble Creek in 2001. We found a significant offspring size-number trade-off at Ball Gulf, while at Hardscrabble Creek this trade-off was marginally significant in 2001 and non-significant in 2000.
Seasonal fluctuations, phenology and diet of Misumenops argenteus (Araneae, Thomisidae) on Trichogoniopsis adenantha (Asteraceae) were investigated in the Serra do Japi, southeastern Brazil, over a 2 year period. This spider population increased at the beginning of the rainy season, reaching a peak in March, and decreased in May, reaching its lowest density in the cold/dry season. In the rainy season (December–May), most of the individuals were in the young or juvenile phase (3rd–6th instars). The spiders reached adulthood between the end of the cold/dry season and the beginning of the hot/rainy season. Analysis of temporal displacement (with up to a 3 month delay) detected a one month delay between the blooming period of T. adenantha and the beginning of the rainy season. The number of arthropods (potential prey of M. argenteus) on the plants increased concomitantly with the increase in the number of reproductive branches. The M. argenteus population also increased numerically 2 months after the rise in arthropod density. These results indicate that the spiders require time to respond to changes in environmental conditions. Of the 595 spiders examined, 76 (12.8%) had prey. Prey items included arthropods belonging to several guilds, but spiders showed a preference for wingless prey or prey that remained on the branches for longer periods of time.
The pholcid spider Holocnemus pluchei (Scopoli 1763) competes for food with conspecifics, and spiders reared on high food levels are generally larger. In this study, we examined whether larger female body size (as estimated by tibia-patella length) translated into increased reproductive success in the form of increased clutch size, clutch weight, and average egg weight. Larger spiders had more eggs and thus heavier clutches, but there was no relationship between maternal size and average egg weight. We also looked for a tradeoff between average egg weight and egg number, and we found a weak relationship in which average egg weight was highest for intermediate-sized clutches. Larger female body size thus translates into increased reproductive success in terms of egg number and clutch weight, but not weight of individual eggs.
Oedothorax gibbosus (Blackwall 1841) (Erigoninae, Linyphiidae, Araneae) is a dwarf spider characterized by dimorphic males. There is a “gibbosus” male morph characterized by a hunch on the posterior third of the carapace, anterior to which is a hairy groove, and a “tuberosus” morph without these features. We observed several gustatorial courtship interactions by a gibbosus male morph and a conspecific female as well as a by a gibbosus male and a male of the closely related species, Oedothorax fuscus (Blackwall 1834). These interactions suggest that the hairy groove in the gibbosus male morph is a nuptial feeding device possibly under the influence of sexual selection. The interspecific interactions can possibly be interpreted as ‘robbings' of the nuptial feeding. The interspecific interactions indicate that the cephalic structure of gibbosus probably does not function as a “lock and key” mechanism.
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