Abstracts to Articles

The Journal of Arachnology

Volume 30 Number 1

Stylocellus ramblae, a new stylocellid (Opiliones, Cyphophthalmi) from Singapore, with a discussion of the Family Stylocellidae

by Gonzalo Giribet

ABSTRACT. A new Stylocellus from Singapore, the smallest species of the genus, is described and fully illustrated. The family Stylocellidae is rediagnosed and emended to include the representatives of the genera Miopsalis and Fangensis based on the results of a phylogenetic analysis of the cyphophthalmid genera (Giribet & Boyer 2002).

Keywords: Cyphophthalmi, Stylocellidae, Stylocellus, Miopsalis, Fangensis, Leptosalis

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How spider anatomy and thread configuration shape the stickiness of cribellar prey capture threads

by Brent D. Opell

ABSTRACT.Cribellar threads are primitive prey capture threads formed of thousands of fine, looped cribellar fibrils that surround larger, supporting fibers. Cribellar fibrils are produced from the spigots of an abdominal spinning field, the cribellum, which may be either a single, oval plate or a pair of medially divided plates. The number of spigots on a spider's cribellum is known to be directly related to the stickiness of its cribellar thread. Some spiders deposit cribellar threads in their webs as taut, self-supporting linear threads; others deposit looped threads along a supporting foundation thread. This study showed that the looped cribellar threads of Kukulcania hibernalis (Filistatidae) and Mexitlia trivittata (Dictynidae) were wider and stickier than linear threads produced by Waitkera waitakerensis and Uloborus glomosus (Uloboridae), respectively, that had the same numbers of cribellum spigots. Linear cribellar thread spun from the divided cribellum of K. hibernalis was both wider and stickier than linear thread spun from the undivided cribellum of W. waitakerensis that had the same number of spigots. A single cribellar plate of K. hibernalis and the cribellum of Siratoba referena (Uloboridae) had a similar number of spigots and produced cribellar threads with similar stickiness. Thus, both a spider's spinning anatomy and its spinning behavior affect the stickiness of its cribellar threads.

Keywords: Cribellum, spigot number, thread stickiness

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Body condition and mate choice in Tetragnatha elongata (Araneae, Tetragnathidae)

by Anne Danielson-François, Christine A. Fetterer & Peter B. Smallwood

ABSTRACT. The mate preference characteristics of adult Tetragnatha elongata were assessed with respect to measures of female mass, linear size (length), and condition (mass scaled by length: body condition). Males preferred longer, heavier females and females with higher body condition indices. When mass is partially controlled, males still preferred females of higher body condition, but reversed their preference for length and chose smaller females. We present evidence that female body condition and mass are associated with the volume of her egg load and the proximity of oviposition, whereas female body length is not associated with either. Females displayed no clear preference among males for mass or linear size, but were reluctant to mate in female-choice trials. The small sample size obtained may have obscured the detection of female mate preferences if they exist. This may be the first evidence that mate choice is influenced by body condition rather than mass or linear size among spiders.

Keywords: Mate choice, size, body condition, oviposition, Tetragnatha elongata

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Population dynamics of two species of kleptoparasitic spiders under different host availabilities

by Tadashi Miyashita

ABSTRACT. Kleptoparasitic spiders are known to have a close association with host spiders, yet there have been few studies demonstrating how host availability influences the dynamics of kleptoparasites. Field surveys were conducted at five sites differing in host composition in sub-tropical areas in Japan, at about two-months intervals. Argyrodes flavescens and A. bonadea were both found more frequently on webs of two Nephila species than expected from the web areas they occupied among webs of all web spiders. Seasonal dynamics of Argyrodes changed greatly according to whether N. clavata was present or not, indicating the importance of Nephila on Argyrodes populations. The peak density of A. bonadea came earlier than that of A. flavescens. Because A. flavescens is known to limit the number of A. bonadea on host webs, the decrease in the density of A. bonadea may be due to the effect of interspecific competition by A. flavescens.

Keywords: Interspecific competition, parasite, Theridiidae, phenology

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Lack of task differentiation during prey capture in the group living spider Stegodyphus mimosarum (Araneae, Eresidae)

by Cheron Ainsworth, Rob Slotow, Tanza Crouch & Yael Lubin

ABSTRACT.Stegodyphus mimosarum of the African savanna form communal nests consisting of few to several hundred individuals and co-operate in nest construction and maintenance, brood care and prey capture. We tested large and small individuals for differential responses to different prey risk types. To date, there has been no conclusive evidence of tasking in these or other social spiders. If tasking occurs, small spiders should approach and attempt to subdue less dangerous prey items such as flies more often than the more dangerous prey items such as bees. Hungry individuals were significantly more willing to venture out of the nest refuge and thus accept the costs associated with prey capture than were satiated spiders. Apparent depletion of poison in previous prey captures did not significantly affect an individual's response to a prey item. Spiders treated more dangerous prey (bees) more carefully than less dangerous prey (flies), but there was no difference in the response of large versus small spiders to prey. The two-way interaction between spider size and prey type was never statistically significant, indicating a lack of tasking in this species.

Keywords: Foraging, co-operation, social, communal

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Cytogenetic heterogeneity in common haplogyne spiders from Argentina (Arachnida, Araneae)

by Sergio Gustavo Rodriguez Gil, Liliana María Mola, Alba Graciela Papeschi & Cristina Luisa Scioscia

ABSTRACT. The spermatogenesis of four species of haplogyne spiders from Argentina is analyzed. Dysdera crocota (Dysderidae) (n 5 5 1 X0) has holokinetic chromosomes, achiasmatic male meiosis and a post-reductional division of the sex chromosome. Ariadna boesenbergii (Segestriidae) (n 5 4 1 X0) also possesses holokinetic chromosomes, but meiosis is chiasmatic and the X chromosome divides pre-reductionally. Kukulcania hibernalis (Filistatidae) (n 5 11 1 X1 X2 0) and Scytodes globula (Scytodidae) (n 5 6 1 X0) have metacentric and submetacentric chromosomes, chiasmatic meiosis and the sex chromosomes divide pre-reductionally. Kukulcania hibernalis possesses a bimodal karyotype and a particular chromatin coiling during prophase I, while Scytodes globula has striking proximal localization of chiasmata. These results show that Haplogynae present high cytogenetic heterogeneity: species with holokinetic chromosomes as well as species with monocentric chromosomes (metacentric and submetacentric), and species with low diploid numbers, achiasmatic meiosis and proximal chiasma localization.

Keywords: Haplogyne, cytogenetics, meiosis

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Validation of a simple method for monitoring aerial activity of spiders

by Pernille Thorbeck, Chris J. Topping & Keith D. Sunderland

ABSTRACT. Many species of spider disperse by ballooning (aerial dispersal), and indices of aerial activity are required in studies of population dynamics and biological control in field crops where spider immigrants are needed for pest suppression. Current methods (e.g., suction traps, sticky traps, deposition traps) of monitoring aerial activity are very labor-intensive, expensive, or require a power supply. We tested Ballooning Index (BI), an alternative, simple method utilizing inexpensive equipment. This method involved the monitoring of spiders climbing an array of 30 cm tall wooden sticks placed vertically in short turf. During a two-year study in arable land in the UK, the incidence of spiders (mainly Linyphiidae) on sticks was correlated with the numbers caught at 1.4 m and 12.2 m above ground in suction traps. Climbing activity on sticks was greater during the morning than in the afternoon, and this activity started progressively earlier in summer than in winter. There was no seasonal change in the proportion of spiders caught at the two heights in suction traps. The pattern of catches (on sticks and in suction traps) suggested strongly that the majority of ballooning spiders dispersed by a number of short flights, rather than by a single long flight, and that segregation of immigrants and emigrants is not possible by any current method. The BI method appears to be, however, a simple and reliable technique for monitoring the overall aerial activity of ballooning spiders.

Keywords: Aerial dispersal, ballooning height, seasonal variation, Linyphiidae, Araneae

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A test for reproductive separation of alternative generations in a biennial spider, Araneus diadematus (Araneae, Araneidae)

by Jes Johannesen & Søren Toft

ABSTRACT. In Denmark, two seemingly distinct size-classes, 3 rd and 4 th instar juveniles and reproductive adults, of Araneus diadematus are found during every breeding season in autumn, indicating a non-overlapping biennial life-cycle. We tested the hypothesis that alternate generations might experience a degree of reproductive isolation, using the distribution of nuclear (allozyme) and maternal (mtDNA) genetic markers. Individuals of a locality behaved as belonging to a random mating population, irrespective of size. No differences were found between any size-class pairs, within and between 2 yr, or among geographically distant samples. Processes that may lead to this result are discussed: the biennial development may be incomplete; or there may be migrational influx of genes from southern annual populations. There is no evidence for sexual differences in life-cycle length.

Keywords: Araneae, life history, biennial reproduction, mitochondrial DNA, allozymes

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Estimation of capture areas of spider orb webs in relation to asymmetry

by Todd A. Blackledge & Rosemary G. Gillespie

ABSTRACT. We examined the utility of several popular formulae used to estimate the capture areas of orb webs across a large sample of Cyclosa Menge 1866 and Tetragnatha Latreille 1804 webs. All formulae evaluated contained at least some bias in estimation of the capture areas of webs. We identified two types of asymmetry in orb webs that affect capture area estimation differently. Web asymmetry measures the ratio of the horizontal and vertical diameters of orb webs while hub asymmetry measures the displacement of the hub from the geometric center of a web. An analysis of model webs that varied in web and hub asymmetry showed that most formulae overestimated capture area as web asymmetry increased and that some formulae also overestimated capture area as hub asymmetry increased. Only the ''Ellipse-Hub'' formula was unaffected by web and hub asymmetry. Although the ''Adjusted Radii-Hub'' formula provided a slightly more accurate overall estimate of capture area, we recommend that the ''Ellipse-Hub'' formula be used when comparisons of capture area are made between taxa or individuals that vary in web and hub asymmetry.

Keywords: Web architecture, asymmetry, sticky silk, capture spiral, spider web

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Acrographinotus mitmaj, a new harvestman species from central Peru (Opiliones, Gonyleptidae, Pachylinae)

by Luis Eduardo Acosta

ABSTRACT. This paper presents the description of the new species, Acrographinotus mitmaj (Opiliones, Gonyleptidae, Pachylinae). It can be easily distinguished from its congeners by: male femur IV long and spiny, devoid of the rows of tubercles and/or apophyses characteristic of other nominal species in the genus; further, A. mitmaj new species bears a less developed median apophysis on the 3 rd free tergite (larger armature in other species). Penis morphology (especially concerning the ventral process of the stylus) agrees with the generic diagnosis. Known localities of the new species are restricted to the upper Río Cañete valley (Departamento Lima, central Peru).

RESUMEN. Se describe la nueva especie Acrographinotus mitmaj (Opiliones, Gonyleptidae, Pachyli-nae). Ésta puede distinguirse fácilmente de otras especies en el género por el fe´mur IV del macho, largo y espinoso, sin las hileras de tubérculos y/o apófisis que caracterizan a los otros Acrographinotus; asimismo, A. mitmaj n. sp. presenta la apófisis mediana del 3er tergito libre menos desarrollada (dicha apo´fisis es mayor en otras especies). La morfología del pene (en especial del proceso ventral del stylus) concuerda con la diagnosis genérica. Las localidades conocidas de la nueva especie se limitan al valle superior del Río Cañete (Departamento Lima, Peru´ central).

Keywords: Opiliones, Gonyleptidae, Acrographinotus, Peru´, Andes

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New species of Eremobatidae (Arachnida, Solifugae) from North America

by Jack O. Brookhart & Paula E. Cushing

ABSTRACT. Five new species of Solifugae are described from North America: Eremobates chihuaensis, Eremobates gerbae, Hemerotrecha sevilleta, Hemerotrecha cornuta, Eremochelis oregonensis as well as the females of Eremocosta gigasella (Muma, 1970), and Eremobates polhemusi Muma & Brookhart, 1988.

Keywords: Taxonomy, solpugida, camel spiders, sun spiders, wind scorpions

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Orobothtirus atiquipa, a new bothriurid species (Scorpiones) from Lomas in southern Peru

by José Antionio Ochoa & Luis Eduardo Acosta

ABSTRACT. Orobothriurus atiquipa new species (Scorpiones, Bothriuridae) from Lomas formations in the coastal desert of southern Peru´ is described and illustrated. This species belongs to the alticola species-group, and within the group, it is closely related to O. alticola (Pocock), O. paessleri (Kraepelin) and O. curvidigitus (Kraepelin). The spine formula (4 1 3) on tarsi III­IV is probably an autapomorphy for the new species. Some features of the habitat (the Lomas formation are green isolates in the coastal desert), as well as a distribution map are provided.

RESUMEN. Se describe Orobothriurus atiquipa nueva especie de escorpión Bothriuridae, colectado en una formación de Lomas en el desierto costanero del Sur del Peru´. Esta especie pertenece al grupo alticola; dentro de éste, las especies más próximas son O. alticola (Pocock), O. paessleri (Kraepelin) y O. curvidigitus (Kraepelin). La fórmula de espinulación tarsal en patas III­IV (4 1 3) es probablemente una autapomorfia de la nueva especie. Se presentan también algunos datos del habitat de O. atiquipa (las formaciones de Lomas son verdaderos parches de vegetación dentro del desierto costero), así como un mapa de distribucíon.

Keywords: Scorpiones, Bothriuridae, Orobothriurus, Peru´, Neotropics

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Redescription of Metacleobis fulvipes Roewer from Brazil (Solifugae, Mummucidae)

by Lincoln Suesdek Rocha & Eliana Marques Cancello

ABSTRACT. The species Metacleobis fulvipes Roewer 1934 (Solifugae, Mummuciidae), previously known only from the male holotype, is redescribed based on the holotype and other male and female specimens. Illustrations of the main diagnostic characters are provided, and new occurrences of this species in Brazil are reported. Some behavioral observations of one individual kept in a terrarium are given.

RESUMO. A espécie Metacleobis fulvipes Roewer 1934 (Solifugae, Mummuciidae), conhecida previamente apenas pelo holótipo macho, é redescrita a partir do holótipo e de outros exemplares machos e fêmeas. Ilustraçõ es dos principais caracteres são fornecidas e novas ocorrencias da espécie no Brasil são registradas. São descritas observaçõ es comportamentais feitas a partir de um indivíduo mantido em terrário.

Keywords: Solifugae, Solpugida, Mummuciidae, taxonomy, Brazil

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A cladistic analysis of the cyphophthalmid genera (Opiliones, Cyphophthalmi)

by Gonzalo Giribet & Sarah L. Boyer

ABSTRACT. A phylogenetic analysis of the genera of Cyphophthalmi is undertaken by studying 32 morphological characters in 43 species representing all families and most genera. The analysis is comple-mented with a molecular analysis using 18S rRNA and 28S rRNA sequence data of twelve cyphophthalmid species representing ten genera. The Cyphophthalmi are monophyletic, as are the families Stylocellidae and Pettalidae. However, the families Sironidae, Ogoveidae, and Neogoveidae are not monophyletic. Relationships among families need more data, but molecular characters strongly support the monophyly of Troglosironidae + Neogoveidae. Rooting the cyphophthalmid tree by using sequence data of one Eupnoi, one Dyspnoi, and one Laniatores results in two alternatives, one proposing a sister group relationship of Stylocellidae to the remaining taxa, or alternatively Pettalidae (with Suzukielus?) as sister group of the remaining cyphophthalmids. The position of Troglosiro, Suzukielus, Metasiro, Huitaca, and the epigean ''Neogovea'' mexasca are re-evaluated and discussed.

Keywords: Cyphophthalmi, systematics, molecular data, morphological data, cladistics

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The African spider genus Singafrotypa (Araneae, Araneidae)

by Matjaz Kuntner & Gustavo Hormiga

ABSTRACT. The African spider genus Singafrotypa Benoit is redescribed and transferred from the tetragnathid subfamily Nephilinae to the araneid subfamily Araneinae. Cladistic analysis of the matrix of Scharff & Coddington (1997) with the addition of two Singafrotypa species supports this new placement. Singafrotypa acanthopus Simon, the type species of the genus, is described along with two new species: Singafrotypa okavango new species from Botswana, and Singafrotypa mandela new species from South Africa. Singafrotypa goliath Benoit is transferred to Neoscona Simon (Araneidae, Araneinae).

Keywords: Araneae, Singafrotypa, Neoscona, Araneidae, Araneinae, Nephilinae, Tetragnathidae, cladistics, Africa

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The copulatory organs of the cryptic species Lycosa carbonelli and their hybrid progeny, with notes on their taxonomy (Araneae, Lycosidae)

by Miguel Simó, Rosina Seguí & Fernando Pérez-Miles

ABSTRACT. The copulatory organs of the cryptic species Lycosa thorelli and Lycosa carbonelli are studied and are shown to exhibit some differences. The morphology of the epigynum, vulva and palpal organs of L. carbonelli are here described for the first time. Additional morphological data of these species are provided and the specific diagnosis reformulated. Measurements indicated that the copulatory organs of L. carbonelli are larger than L. thorelli. Morphological comparison between the parental species and the hybrid progeny show that hybrids are intermediate in morphology and size. The reproductive isolation in these cryptic species and the inheritance of the sexual characters in the hybrid progeny are discussed.

Keywords: Lycosa carbonelli, L. thorelli, copulatory organs, taxonomy, hybrids

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Adult size of eight hunting spider species in central Amazonia: temporal variations and sexual dimorphisms

by Thierry Ray Gasnier, Clarissa Salette de Azevedo, Martha Patricia Torres-Sanchez & Hubert Höfer

ABSTRACT. We studied temporal variation in adult size and sexual size dimorphism (SSD) of seven hunting spider species, Ctenus amphora, C. crulsi, C. manauara, C. villasboasi (Ctenidae), Phoneutria fera, P. reidyi (Ctenidae), and Ancylometes rufus (Pisauridae) in a tropical rainforest, and one species from a relatively open vegetation habitat, C. minor, in central Amazonia. Size variation was great within and among field trips. Spiders were generally smaller in October (end of dry season) when compared with other months: adults of C. amphora, C. crulsi and C. manauara were significantly smaller in October 1995 when compared to February 1996; P. fera were smaller in October 1998 than in June 1998; and A. rufus were smaller in October 1998 than in August 1998. The temporal variation in size is possibly a result of low prey availability during the dry season. Six species had significant differences in prosoma length between males and females: C. amphora, C. crulsi, C. manauara and C. minor had larger males (which is considered rare in spiders), and P. reidyi and P. fera had larger females. However, considering an alternative index of size, the ''rough area'' (an approximate measure of the area of the spider as seen from above), the males were significantly larger for all species (up to 2.8 times in C. minor), because they have longer legs relative to their prosoma length. We suggest that selection for high mobility may be the reason for adult males with longer legs, and that the smaller species had higher degrees of sexual dimorphism in leg length because of the relative size of obstacles in the leaf litter.

RESUMO. Estudamos a variação temporal de tamanho de adultos e o dimorfismo sexual de tamanho de sete espécies simpátricas de aranhas errantes, Ctenus amphora, C. crulsi, C. manauara, C. villasboasi (Ctenidae), Phoneutria fera, P. reidyi (Ctenidae), e Ancylometes rufus (Pisauridae) em uma floresta tropical u´mida, e uma espécie em um habitat de vegetação relativamente aberta, C. minor, na Amazonia Central. A variação de tamanho foi grande dentro e entre excurso"es de coleta. As aranhas foram geralmente menores em outubro (final da estação seca) comparado com outros meses: adultos de C. amphora, C. crulsi, C. manauara e C. minor foram significativamente menores em outubro de 1995 comparado a fevereiro de 1996: P. fera foram menores em outubro de 1998 do que em junho de 1998 e A. rufus foram menores em outubro de 1998 do que em agosto de 1998. A variação temporal em tamanhos observada e´ possivelmente um resultado de baixa disponibilidade de presas durante a estação seca. Seis espécies tiveram diferenças significativas em comprimento do cefalotórax entre machos e femeas, C. amphora, C. crulsi, C. manauara e C. minor tiveram machos maiores (o que é considerado raro em aranhas), P. reidyi e P. fera tiveram femeas maiores. Entretanto, considerando um índice alternativo de tamanho, a ''área aproximada'' (uma medida da área da aranha em vista superior), os machos foram significativamente maiores em todas as espécies (até2,8 vezes em C. minor), porque eles te m pernas mais longas em relaç ão ao tamanho do cefalotórax. Nós sugerimos que uma seleç ão para alta mobilidade pode ser a razão paramachos com pernas maiores, e que as menores espécies tem maior dimorfismo sexual no comprimento das pernas devido ao tamanho relativo dos obstáculos na serapilheira.

Keywords: Ancylometes, Ctenus, Ctenidae, Phoneutria, Pisauridae, seasonality, sex ratio, sexual-size-dimorphism, wandering spiders

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Chemosensory response to prey in Phiddipus audax (Araneae, Salticidae) and Pardosa milvina (Araneae, Lycosidae)

by Chad D. Hoefler, May Taylor & Elizabeth M. Jakob

ABSTRACT.Many predators exploit the chemical signatures of prey when foraging. We present a comparative study designed to test if the foraging behavior of Phidippus audax (Hentz 1845) is manipulated by substrate-borne chemicals left by prey. Our findings suggest that foraging P. audax do not use chemical cues left by prey, while the wolf spider Pardosa milvina (Hentz 1844) in the same experimental setup does respond to chemical cues. However, further examination into the role of chemical cues on prey detection in salticids is required.

Keywords: Salticidae, Lycosidae, foraging, chemical cues

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Hawaiian spiders of the genus Tetragnatha: IV new, small species in the spiny leg clade

by Rosemary G. Gillespie

ABSTRACT. This study continues documentation of the adaptive radiation of species in the genus Tetragnatha in the Hawaiian archipelago. The five new species described here are representatives of the 'spiny-leg' clade, most representatives of which have already been described. The new species are T. kukuiki, T. kikokiko, T. anuenue, T. kukuhaa, and T. obscura. The species described are found in various different habitat types from low (e.g., 550 m on Oahu) to middle elevations (1660 m on Hawaii), and from dry to very wet forest types. As with other representatives of the clade, they are nocturnal hunters, do not build webs, and move actively around the vegetation.

Keywords: Hawaii, Tetragnatha, spiny, descriptions

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A new species of Pseudotrogulus Roewer and assignment of the genus to Hernandariinae (Opiliones, Gonyleptidae)

by Carlos Leandro Firmo & Ricardo Pint-da-Rocha

ABSTRACT. Pseudotrogulus funebris, new species, is described from Estação Biológica de Paranapia-caba (Santo André, State of São Paulo, Brazil). P. funebris differs from other species of the genus by the presence of a large number of tubercles on area I close to the median groove, area III with tubercles concentrated in the median region, tergite III with a large rhomboid tubercle and tarsus III-IV with 8 articles. Pseutrogulus is newly transferred to Hernandariinae based on the following characteristics: 1) median-anterior tubercles on anterior margin pointing upwards; 2) large tubercles on lateral-anterior mar-gin; 3) eye mound with two tubercles upward.

Keywords: Hernandariinae, Neotropics, Opiliones, Pseudotrogulus

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Notes on the foraging behavior of the Brazilian cave harvestman Goniosoma spelaeum (Opiliones, Gonyleptidae)

by Flávio H. Santos & Pedro Gnaspini

ABSTRACT. Goniosoma spelaeum (Mello-Leita"o 1932) hide in caves during the day and leave periodically after dusk to forage, moving mainly vertically (towards the canopy). When stopped, individuals of all developmental stages often showed the behavior of cleaning appendages. To hunt, some specimens remained for several hours in a static posture with all legs spread out, radially disposed. In a less frequently used hunting position the body is used as a ''web'' i.e., the animal is supported by two opposing leaves, leaving its body between them, while legs II are kept free in the air and moving constantly. The first position possibly increasing the chance of meeting a possible prey by creating a larger area of contact, and the second especially by intercepting flying insects. Food items observed being taken in nature include: noctuid lepidopterans, tipulid and nematoceran dipterans, ascalaphid neuropterans, and isopods. They also infrequently use their chelicerae to chew on the rim of leaves and/or pieces of moss, with no ingestion of plant matter. Therefore, this behavior is probably related to drinking.

Keywords: Goniosoma, hunting behavior, foraging behavior, Opiliones, Gonyleptidae

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This page was posted 6 / 28 / 2002 and modified 11 / 27 / 2009