Electronic Library of
Volume 19 / Suppl. 3 / 2000
Trine Bilde, Soren Toft
Department of Zoology, University of Aarhus, Building 135, DK-8000 Arhus C, Denmark. E-mail: firstname.lastname@example.org
Bilde T., Toft S.: Evaluation of prey for the spider Dicymbium brevisetosum Locket (Araneae: Linyphiidae) in single-species and mixed-species diets. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 9-18.
The objective of this study was to asses effects of dietary mixing of prey of different
quality for a generalist predator. Prey of three qualities were tested in
single-species and mixed-species diets: the cereal aphid Rhopalosiphum padi as
a low quality prey, and two qualities of fruit flies Drosophila melanogaster
representing intermediate quality (Normal flies) and high quality (Enriched flies) prey.
The two types of fruit flies were obtained by rearing the flies on different media. It was
expected that aphids might contribute positively to the diet of intermediate quality
flies, but contribute nothing or negatively to that of high quality flies. The value of
prey was assessed by fitness parameters in an egg production experiment. Females of the
linyphiid spider Dicymbium brevisetosum were assigned to one of 6 diet
treatments: 1) Normal D. melanogaster, 2) Normal D. melanogaster + R.
padi, 3) Enriched D. melanogaster, 4) Enriched D. melanogaster
+ R. padi, 5) R. padi, and 6) R. padi added to Normal
D. melanogaster until the first eggsac appeared, then only R. padi. The
following parameters were recorded: no. of egg sacs per female, no. of eggs/sac, and
hatching success. Females on single-species diets of aphids produced fewer eggsacs
containing fewer eggs than spiders on fruit fly diets. Normal flies supported a high
egg laying rate but low hatching success compared to Enriched fruit flies. Mixing aphids
with Normal fruit flies had no effect on the measured fitness parameters, whereas mixing
aphids with Enriched flies resulted in a lower total production of spiderlings
suggesting a toxic effect of aphids on spiders.
A survivorship experiment with hatchlings was conducted in order to investigate the effect of maternal diet on the offsprings´ ability to utilise a low quality prey (R. padi). Two hatchlings from each of the first eggsacs produced by females in the egg production experiment on diet treatments 1) Normal D. melanogaster, 2) Normal D. melanogaster + R. padi, 3) Enriched D. melanogaster, and 4) Enriched D. melanogaster + R. padi, were kept individually on a diet of R. padi and survival time was recorded. Maternal diet affected survival of those offspring feeding exclusively on R. padi. A lower survival was found on offspring from females reared on Normal fruit flies compared to Enriched fruit flies, thus quality of offspring may vary with that of maternal diet. The results emphasise that effects of dietary mixing depend on the characteristics of the prey types composing the diet. Negative effects of adding aphids to Enriched flies was found by a lowered hatching success, while positive effects of adding aphids to Normal flies was found in the survival of offspring.
Pcta. Metalúrgicos, 2, 1° Dto., 2835-043 Baixa da Banheira, Portugal. E-mail: email@example.com
Cardoso P.: Portuguese spiders (Araneae): a preliminary checklist. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 19-29.
With 642 described species and 8 subspecies, continental Portuguese spiders are still poorly known. A preliminary species checklist is presented and the country is evaluated in terms of its known spider species distribution. What has been done and what has to be done are two of the main topics to be addressed.
Pcta. Metalúrgicos, 2, 1° Dto., 2835-043 Baixa da Banheira, Portugal. E-mail: firstname.lastname@example.org
Cardoso P.: Description of the supposed male Nemesia hispanica L. Koch in Ausserer, 1871 (Araneae: Nemesiidae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 31-36.
The first description of Nemesia hispanica was by L. Koch and appeared in Ausserer, 1871. However, until now it has only been known from the female. During a study carried out in the Arrábida region of Portugal the author has collected what is thought to be the male of this species. It is described here for the first time. Some considerations of morphology, distribution and taxonomic relationships are briefly presented.
Sergei N. Danilov
Institute of General and Experimental Biology, Russian Academy of Sciences, Sakhyanova str. 6, Ulan-Ude 670047, Russia.
Danilov S.N.: New data on the spiders of the family Dictynidae (Araneae) from Siberia. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 37-44.
Four species of dictynid spiders are described from South Siberia: Dictyna paramajor sp.nov. (Krasnoyarsk Prov.), Dictyna dunini sp.nov. (Buryatia), Dictyna dahurica sp.nov. (Chita Area), Dictyna shilenkovi sp.nov. (Irkutsk Area, Buryatia). The female of Emblyna mongolica Marusik et Koponen, 1998 is described for the first time. New records are presented for Argenna prominula Tullgren, 1948, Dictyna alaskae Chamberlin et Ivie, 1947, Dictyna schmidti sensu Lethinen, 1967 and Dictyna ubsunurica Marusik et Koponen, 1998. Emblyna logunovi Marusik et Koponen, 1998 is synonymised with Emblyna wangi (Song et Zhou, 1986) comb.nov. (ex. Dictyna).
Domir De Bakker, Jean-Pierre Maelfait, Frederik Hendrickx, Dries Van Waesberghe, Bruno
De Vos, Sofie Thys, Luc De Bruyn
Royal Belgian Institute of Natural Sciences, Department of Entomology, Vautierstraat 29, B-1000 Brussels, Belgium. Fax: +32 (0)2/627 41 32. E-mail: email@example.com
Ghent University, Department of Biology, Laboratory of Ecology, Zoogeography and Nature Conservation, K.L Ledeganckstraat 35, B-9000 Ghent, Belgium. Fax: +32 (0)9/264 53 43, E-mail: firstname.lastname@example.org, email@example.com
Institute of Nature Conservation, Kliniekstraat 25, B-1070 Brussels, Belgium. Fax: +32 (0)2/558 18 05. E-mail: firstname.lastname@example.org
Institute of Forestry and Game Management, Gaverstraat 4, B-9600, Geraardsbergen, Belgium. E-mail: email@example.com
University of Antwerp (RUCA), Department of Evolutionary Biology, Groenenborgerlaan 171, B-2020 Antwerp, Belgium. E-mail: firstname.lastname@example.org, email@example.com
De Bakker D., Maelfait J.-P., Hendrickx F., Van Waesberghe D., De Vos B., Thys S., De Bruyn L.: A first analysis on the relationship between forest soil quality and spider (Araneae) communities of Flemish forest stands. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 45-58.
A project aiming at the development of a practical bio-indication system for evaluating forest soil quality was recently started up. The project is funded by the Flemish Forestry Administration responsible for the protected Flemish forests and is managed by the Institute for Forestry and Game Management (IBW). In the project the arthropod fauna of fifty forest stands distributed all over the Flemish Region was sampled by traps operative from spring 1997 till spring 1998. All these plots were also investigated in relation to the physical and chemical properties of their soil and litter layers. The variation of the composition of the spider communities of these stands is unclear when we compare it with the most important litter and soil parameters, but future investigations with more (structural) parameters will hopefully give a good explanation. On a subregional scale, in forests on the same soil type (loam), spider community composition seems to be determined by humidity and density of tree coverage. Spider species forwhich abundance correlates with these major environmental factors are candidate bio-indicators to monitor forest soil quality.
Institute of Zoology, Bulgarian Academy of Sciences, bld Tsar Osvoboditel 1, 1000-Sofia, Bulgaria. Fax: +359-2-882-897. E-mail: firstname.lastname@example.org
Deltshev C.: The endemic spiders (Araneae) of the Balkan peninsula. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 59-65.
The endemic taxa of spiders (Araneae) in the Balkan peninsula are represented by 348 species included in 30 families. Countries with the highest number of recorded endemic species are Greece (115), Croatia (68), Bulgaria (55), Bosnia (41), Crete (46). The distribution of the endemic spiders in the main geographic systems of the Balkan peninsula shows that they are best represented in the Pindus region 150, Dinaric region 145, Tracian-Macedonic region 52, Balkanid region 14, Danubian region 4 and North Dobrudzha with 4 species. The largest proportion of endemics was encountered mainly in the mountains and islands, where they inhabit caves 159, woodlands 139, coastal sites 48 and high altitude zones 20 species. The extreme richness of troglobitic spiders in the Dinaric region (96) leads to the assumption that this was a major center of speciation and evolution of species. The same can be said for the forest of the Pindus region (74) and for the highest mountains (Rila, Pirin) of the Tracian-Macedonic region, where are found the greatest number of high altitude elements (15). The phenomenon can be regarded as a result of the relative isolation of the mountains compared with the lowland areas, in the context of paleo-environmental changes since the Pliocene. The high percentage of endemic spiders (25%) suggests an important process of autochthonous speciation. So the Balkan Peninsula can be considered as a main center of speciation in Europe.
Jason A. Dunlop
Institut für Systematische Zoologie, Museum für Naturkunde der Humboldt-Universität zu Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. Fax: + 49 30 2093 8528. E-mail: email@example.com
Dunlop J.A.: The epistomo-labral plate and lateral lips in solifuges, pseudoscorpions and mites. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 67-78.
Solifugae and Pseudoscorpiones are accepted by most recent authors as sister taxa, forming a clade Haplocnemata. The sister group of Haplocnemata is less certain. Most recent authors have accepted Acari as monophyletic and placed them as sister group of Ricinulei, although a (Ricinulei + Trigonotarbida) relationship has also been proposed. In an attempt to resolve some of these phylogenetic questions, the mouthparts of Solifugae, Pseudoscorpiones and Acari were investigated. In these three orders the mouth is covered dorsally by a projecting epistomo-labral plate (a fused epistome and labrum), and ventrolaterally by a pair of finger-like lateral lips, probably derived from the coxae of the pedipalps. This character complex of a epistomo-labral plate + lateral lips is not seen in other arachnids, although similar, and perhaps homologous structures occur in Opiliones. The epistomo-labral plate + lateral lips are interpreted here as a possible synapomorphy for (Acari (Solifugae + Pseudoscorpiones)).
Alexander V. GROMOV
Laboratory of Entomology, Institute of Zoology MSHE RK, Akademgorodok, Almaty 480060, Kazakhstan. E-mail: firstname.lastname@example.org
Gromov A.V.: Solpugids of the genus Eusimonia Kraepelin, 1899 (Arachnida: Solifugae, Karschiidae) of Central Asia. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 79-86.
This paper presents a review of the genus Eusimonia in the fauna of Central Asia. Two valid species are found to occur in Central Asia: E. divina Birula, 1935 and E. turkestana Kraepelin, 1899. The type specimens of Eusimonia kept in the Zoological Museum (Berlin) and the Zoological Institute of the Russian Academy of Sciences (St. Petersburg) were re-examined. Four species names are newly synonymized: Karschia (?) demokidovi Birula, 1935 with Eusimonia divina Birula, 1935 syn.nov.; Karschia (?) grombczevskii Birula, 1935, Barella birulae Roewer, 1933 and Eusimonia celeripes Hirst, 1908 with Eusimonia turkestana Kraepelin, 1899 syn.nov. Lectotypes are designated for the first time for the following species: Eusimonia divina Birula, 1935; Barella birulae Roewer, 1933 and Karschia (?) grombczevskii Birula, 1935.
Shirley Gurdebeke, Bart Neirynck, Jean-Pierre Maelfait
Ghent University, Lab. of Animal Ecology, K. L. Ledeganckstraat 35, 9000 Ghent, Belgium. E-mail: email@example.com
Institute of Nature Conservation, Kliniekstraat 25, 1000 Brussels, Belgium.
Gurdebeke S., Neirynck B., Maelfait J.-P.: Population genetic effects of forest fragmentation in Flanders (Belgium) on Coelotes terrestris (Araneae: Agelenidae) as revealed by allozymes and RAPD. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 87-96.
Due to an ever-increasing urbanisation, industrialisation, development of road infrastructure and an intensive agriculture, forests in Flanders have become heavily fragmented. In general, organisms bound to small forest fragments have a reduced population size and are highly isolated from other populations. To assess the population genetic effects of forest fragmentation, we chose Coelotes terrestris (Wider, 1834) as a model organism, because it is strongly bound to forest habitats. A first attempt to reveal the population genetic structure of this species was made by using allozyme electrophoresis. Only one enzyme (PGI) however showed good interpretable variation. This low degree of polymorphism together with the sometimes-questioned neutrality of allozyme markers made us choose genetic marker (RAPD). Ten forests, with a variable degree of isolation and a variable size were investigated. The majority (allozymes) and all (RAPD) pairwise comparisons of population allele/marker frequencies were significantly different, implying a very high degree of genetic isolation between the spider populations inhabiting the forests. No significant correlation could be found between the genetic diversity of the populations and the size of the forest in which they predominate.
Astrid M. Heiling, Marie E. Herberstein
Institute of Zoology, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria. Fax: +43 1 31336 778. E-mail: firstname.lastname@example.org
Department of Zoology, University of Melbourne, Parkville Victoria 3052, Australia. Fax: +61 3 9344 7909. E-mail: email@example.com
Heiling A.M., Herberstein M.E.: Interpretations of orb-web variability: a review of past and current ideas. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 97-106.
The understanding of web-building behaviour in orb-web spiders has undergone several paradigm shifts. In the past, orb-web construction was assumed to be limited to genetically-controlled design patterns, suggesting that meaningful variation only existed at the species level. Subsequently, it was recognised that variation in web design also exists within species and that this variation was linked to the prey capture ability of webs. Another approach to interpreting individual variation is within a decision-making construct. The web-building decisions of spiders may thus be ruled by algorithms or mechanical constraints. Similarly, individual decisions may reflect foraging strategies aimed to maximise food intake. Our own work suggests that experience in web-building and prey capture may also contribute to individual variation of orb-web design. Using several key publications as well as recently collected data we discuss past and current ideas to interpret orb-web variability.
Eva A. Junker, Ulrich M. Ratschker, Mechthild Roth
Dresden University of Technology, Institute of Forest Botany und Zoology, Chair of Forest Zoology, Pienner Straße 7, D-01737 Tharandt, Germany. Fax: ++49 035203 381317. E-mail: firstname.lastname@example.org
Junker E.A., Ratschker U.M., Roth M.: Impacts of silvicultural practice on the ground living-spider community (Arachnida: Araneae) of mixed mountain forests in the Chiemgau Alps (Germany). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 107-117.
Investigations of long-term effects of clear-cutting, as well as slight and heavy
shelterwood cutting, on soil-dwelling spiders were carried out in the mixed mountain
forest of the Bavarian Alps. The experimental design included 4 plots (each of
0.5 ha): a control area (0) without intervention, and three plots, submitted in
1976 to different degrees of canopy opening. Slight (30) or heavy (50) shelterwood cutting
resulted in a 30 or 50% reduction of basal area. On the clear-cut area (100) trees
were completely removed. On each variant a subplot was fenced (Z) subsequently to
silvicultural practice in order to prevent cattle and deer from entering. Spiders were
collected 22 years after the management by pitfall traps (PT: n=9) from April 1998 to
A total of 9750 spiders (97 species, 19 families) was collected, among them 23 Araneae listed in the Red Data Book of Germany and/or Bavaria. Small-sized species of Linyphiidae dominated the spider fauna on each plot. The portion of Lycosidae increased with increasing shelterwood cutting and reached maximum values (18.9%) on 50. The spider community reached its maximum biodiversity on clear-cuts, while the number of specimens as well as the biomass was lowest at these sites. Highest numbers of specimens were found on the unfenced slightly-cut shelterwood plot (30), and the highest biomass on the unfenced plot of heavily-cut shelterwood (50). The Quotient of Similarity (QS), according to Soerensen, decreased with increasing shelterwood cutting and was lowest between 0/Z and 100/Z. The highest similarity was reached between fenced and unfenced plots of the same intensity levels of forestry practice, as well as between the control area (0) and 30% shelterwood cut (30, 30/Z). Using niche width calculations 15 spider species were identified as being characteristic of the clear-cuts (Gnaphosidae: Gnaphosa bicolor, Liocranidae: Agroeca brunnea, Linyphiidae: Agyneta ramosa, Ceratinella brevis, Gongylidiellum latebricola, Lepthyphantes flavipes, Lepthyphantes mansuetus, Lepthyphantes mengei, Micrargus herbigradus, Pocadicnemis pumila, Walckenaeria atrotibialis, Walckenaeria antica, Zoridae: Zora nemoralis) and the heavily-cut shelterwood (Linyphiidae: Diplocephalus picinus, Lycosidae: Alopecosa taeniata). In addition Micrargus apertus was recorded for Bavaria for the first time.
Pavel Kasal, Marie Hladíková, Ambros Hänggi
Department of Medical Informatics, 2nd Medical Faculty, Charles University, V úvalu 84, 150 18 Prague, Czech Republic. E-mail: email@example.com
Museum of Natural History, Basel, Switzerland.
Kasal P., Hladíková M., Hänggi A.: Prediction of spider species occurrence: an example using theridiid spiders (Araneae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 119-124.
An attempt to predict spider species occurrence is described, using theridiid spiders
as an example. Data from the database of Middle European spiders was evaluated to describe
the relationships among the occurrence of spider species using the Jaccard coefficient and
Common non-specific neighbour species are eliminated in this way they are often found with a spider in question but have a minimum indication value. The result of such an analysis is a list of the species occurring regularly with the given spider without any other relation to the features of the habitat. A possible use of such knowledge could be, for instance, the search for a certain species in the given place on the basis of the neighbours occurrence discovered by previous collection.
Institute of Botany, Academy of Sciences of the Czech Republic, Dukelská 135, CZ-379 82 Třeboň, Czech Republic. Fax: +420 333 721136. E-mail: firstname.lastname@example.org
Klime L.: Checklist of harvestmen (Opiliones) of Czechia and Slovakia. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 125-128.
A checklist of harvestmen of Czechia and Slovakia is presented, with notes on selected species. Currently 28 species are known from Bohemia, 30 from Moravia (i.e. 33 from the Czech Republic), and 33 species from Slovakia.
Jacqueline KOVOOR, Arturo MUNOZ-CUEVAS
Laboratoire de Zoologie-Arthropodes, M.N.H.N.-C.N.R.S., 61, rue de Buffon, 75231-Paris Cedex 05, France. E-mail: email@example.com
Kovoor J., Muńoz-Cuevas A.: Comparative histology of the venom glands in a lycosid and several oxyopid spiders (Araneae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 129-140.
The structure and histochemistry of the poison glands are described in Lycosa tarentula (Lycosidae), four Peucetia species and Oxyopes lineatus (Oxyopidae). All these species show two voluminous poison gland sacs which extend dorsally in the prosoma, over the central nervous system, their base reaching up to the central body of the brain. A muscle layer surrounds the gland sac; it is thicker in Lycosa than in the oxyopids and stops at the beginning of the excretory duct. The latter, rather narrow in Lycosa, starts at the base of the chelicera. It forms a secretory ampulla in the last third of the chelicera, then continues its way for about 400 ľm to the entrance of the fang. In oxiopids, the gland sac itself enters the chelicera. An elongated ampulla appears at a quarter (Peucetia) or half (Oxyopes) the length of the cheliceral basal article) and reaches almost the extremity of the chelicera: the excretory duct proper runs only 40 ľm before entering the fang. In all cases, the body of the glands presents two distinct regions secreting different substances. In L. tarentula, the main part of the poison gland secretes a complex protein product, with a fine granular appearance; a small accessory lobe, located ventrally in the proximal region of the gland sac, produces a glycoprotein. In oxyopids, the accessory portion of the gland is much more extensive; both regions produce protein; in the ventral proximal pouch, two substances are detected, one of which appears as flat square crystals, isolated inside the cells but stacked up in the gland lumen. The histological characteristics of the poison glands are examined from a phylogenetic point of view, as well as in relation to the behaviour of these species of hunting spiders.
Wilson R. Lourenço, Dietmar Huber, John L. Cloudsley-Thompson
Laboratoire de Zoologie (Arthropodes), Muséum National dHistoire Naturelle, 61 rue de Buffon 75005 Paris, France. E-mail: firstname.lastname@example.org
P. O. Box 27 A-6811 Göfis, Austria. E-mail: email@example.com
10 Battishill Street, Islington, London N1 1TE, United Kingdom.
Lourenço W.R., Huber D., Cloudsley-Thompson J.L.: Description of the stridulatory apparatus in some species of the genus Rhopalurus Thorell (Scorpiones: Buthidae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 141-144.
Wilson R. Lourenço, Lionel Monod
Laboratoire de Zoologie (Arthropodes), Muséum National dHistoire Naturelle, 61 rue de Buffon 75005 Paris, France. E-mail: firstname.lastname@example.org
Muséum dHistoire Naturelle, Route de Malagnou 1, case postale 6434, CH-1211 Geneve 6, Switzerland
Lourenço W.R., Monod L.: Description of a new genus and species of scorpion (Bothriuridae) from Brazil. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 145-152.
The taxonomic difficulties which can be encountered in the study of scorpions belonging to the family Bothriuridae Simon are discussed briefly. Since the 1960s and 1970s several problems have been elucidated, in particular by San Martin and Maury. A new genus and new species Brazilobothriurus pantanalensis gen. nov. sp. nov., are described from Brazil. Brazilobothriurus pantanalensis is characterised by a unusual trichobothrial pattern of eight ventral trichobothria on each pedipalp chelae. Some information is given on the habitat of the new taxon and on the area where it originates, the Pantanal of Mato Grosso.
David Mayntz, Soren Toft
Department of Zoology, University of Aarhus, Bldg. 135, DK-8000 Arhus C, Denmark. E-mail: email@example.com
Mayntz D., Toft S.: Effect of nutrient balance on tolerance to low quality prey in a wolf spider (Araneae: Lycosidae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 153-158.
The tolerance of the wolf spider Pardosa prativaga to two low quality prey types, the aphid Rhopalosiphum padi (Aphididae) and the collembolan Folsomia candida (Isotomidae), was tested in spiders with different nutrient balance. Good and bad nutrient balance was achieved by feeding the spiders fruit flies raised in cultures of different nutrient content. Spiders with a good balance consumed three times more R. padi than spiders with a bad balance, whereas there was no effect of nutrient balance on the tolerance to F. candida. The rejection behaviour to R. padi and F. candida was tested in spiders of good nutrient balance. The spiders ate more F. candida than R. padi before they refused to attack more prey. Spiders that accepted a fruit fly after the rejection of a low quality prey item were considered to have an aversion against such prey. Of the spiders given R. padi, 76% had or acquired an aversion to them. Only 5% of the spiders had or acquired an aversion to F. candida.
Department of Zoology and Anthropology, Faculty of Biology, University of Sofia, 8 Dragan Zankov Blvd., 1421 Sofia, Bulgaria. E-mail: firstname.lastname@example.org
Mitov P.: Contribution to the knowledge of the harvestmen (Arachnida: Opiliones) of Albania. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 159-169.
The opilionid fauna of Albania is still poorly known. In the entire literature on this topic from the territory of this country are recorded 31 species, some of which have vague taxonomical status or need confirmation. As a result of examination of material from the collections of the author and of the National Museum of Natural History in Sofia, 20 species were established altogether. Ten of these (Paranemastoma titaniacum (Roewer), Mitostoma cancellatum (Roewer), Trogulus nepaeformis (Scopoli), Opilio saxatilis C. L. Koch, Opilio transversalis Roewer, Metaplatybunus carneluttii Hadi, Metaplatybunus strigosus (L. Koch), Rilaena balcanica ilhavý, Lacinius dentiger (C. L. Koch), Amilenus aurantiacus (Simon)) are new to the Albanian fauna. For the other 10 species (Paranemastoma longipes (Schenkel), Mediostoma humerale (C. L. Koch), Trogulus tricarinatus (Linnaeus), Trogulus graecus Dahl, Dicranolasma scabrum (Herbst), Metaphalangium cirtanum (C. L. Koch), Opilio parietinus (De Geer), Metaplatybunus grandissimus (C. L. Koch), Lacinius horridus (Panzer), Nelima troglodytes Roewer) new chorological data are provided.
Arturo Munoz-Cuevas, Pierre Carricaburu
Laboratoire de Zoologie-Arthropodes, MNHN-CNRS, 61 rue de Buffon, 75231 Paris Cedex 05, France. E-mail: email@example.com
21 rue du Commandant Mouchotte, 94160 Saint-Mandé, France.
Munoz-Cuevas A., Carricaburu P.: Electroretinographic modulation by dopamine and noradrenaline in the spider Lycosa tarentula (Araneae: Lycosidae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 171-180.
Injections of dopamine, or noradrenaline, produced modifications of the amplitude, latency and profile of the electroretinograms (ERGs) in a lycosid spider. Each type of eye showed its own ERG modifications. Dopamine-treated anterior-median and lateral eyes showed opposite modifications of the amplitudes of ERGs which increased (AME) or decreased (ALE) compared with controls; the latencies were increased in both cases. Dopamine induced a significant decrease of the amplitudes and an increase of the latencies of ERGs of posterior-median (PM) and lateral (PL) eyes. The effect of noradrenaline was less marked. The antagonist haloperidol produced an opposite effect on ERGs of ALE for all dark adaptation times. The study of visual neuromodulation opens a way towards the control of visually-guided behaviours such as predation, sexual display and orientation in Lycosa tarentula.
University of Innsbruck, Institute for Zoology, Technikerstrasse 25, A-6020 Innsbruck, Austria. E-mail: firstname.lastname@example.org
Muster C.: Arachnological evidence for glacial refugia in the Bavarian Alps. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 181-192.
According to geomorphological conclusions some regions of the Bavarian Alps remained free of ice during the Pleistocene glaciations. The current concepts of phytogeography acknowledge plant survival during cryocratic periods in Bavarian massifs de refuge as well as on the nunatak system. Hitherto in zoogeography, little proof has been offered in support of these assumptions. According to recent investigations the distribution areas of the arachnids Cryphoeca lichenum nigerrima (Hahniidae) and Megabunus lesserti (Phalangiidae) suggest continuous inhabitation of Bavarian refugia since interglacial times. Especially in the Ammergau refugium the persistance of animal life during the last glaciation could be confirmed.
Tânia Nobre, Carola Meierrose
Department of Biology, University of Évora, Mitra, 7002-094 Évora, Portugal.
Nobre T., Meierrose C.: The species composition, whitin-plant distribution, and possible predatory role of spiders (Araneae) in a vineyard in Southern Portugal. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 193-200.
In a vineyard in Southern Portugal, the dominant spider species and their distribution on the plant were investigated. From the 19 spider families present, 61 species were identified, 4 of which were considered to be first records in Portugal. More than 90% of the spiders belonged to 10 species from 7 families. Most spiders were located on the lower surface of leaves, where leafhoppers fed. The predatory capacity of the spiders towards leafhoppers is discussed in the light of some ecological features.
Tânia Nobre, Carola Meierrose, Nuno Gaspar de Oliveira
Department of Biology, University of Évora, Mitra, 7002-094 Évora, Portugal
Nobre, T., Meierrose, C., De Oliveira, N.G.: Comparison of sampling techniques for vineyard foliage spiders (Araneae). In Gajdo, P., Pekár, S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 201-206.
In order to estimate the composition of the foliage spider fauna in a vineyard four concurrent sampling methods (pitfall, yellow sticky trap, drop-cloth technique and standardised visual search) were compared for their suitability. The relative frequency of spider families was different for all the methods used. The chosen methods were compared with regard to spider diversity and to that of the groups targetted by each method. The advantages and disadvantages (including cost effectiveness and animal welfare) of each method were evaluated.
Valentina Petrova, Zigrida Čudare, Ineta teinite
Institute of Biology, University of Latvia, Miera str. 3, Salaspils, LV-2169, Latvia. Fax: +371 9 345412. E-mail: email@example.com
National Botanical Garden, Miera str.1, Salaspils, LV-2169, Latvia. Fax: +371 2 944735. E-mail: firstname.lastname@example.org
Petrova V., Čudare Z., teiníte I.: Seasonal dynamics of predatory mites (Acari: Phytoseiidae) on strawberries in Latvia. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 207-210.
Ten species of phytoseiid mites were found on strawberries during the period 1997-98; Neoseiulus agrestis, N. aurescens, N. barkeri, N. bicaudus, N. cucumeris, N. herbarius, N. reductus, N. zwoelferi, Typhlodromips rademacheri, Propriseiopsis okanagensis. Studies were made of the abundance and seasonal dynamics of phytoseiid species composition.
ValentÍna Petrova, Ineta Salmane
Institute of Biology, University of Latvia, Miera iela 3, Salaspils, LV-2169, Latvia. Fax: +(371 9) 345412. E-mail: email@example.com
Petrova V., Salmane I.: Some mite (Acari) species from mass-rearing laboratories of commercial mushrooms and beneficial arthropods in Latvia. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 211-212.
Ulrich M. Ratschker, Mechthild Roth
Dresden University of Technology, Institute of Forest Botany and Zoology, Chair of Forest Zoology, Pienner Strasse 7, D-01737 Tharandt, Germany. Fax: +49 35203-38-1317. E-mail: firstname.lastname@example.org
Ratschker U.M., Roth M.: Studies on ground dwelling spiders (Araneae) of agrarian habitat types in Northeast Germany: ecological and nature conservation aspects. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 213-225.
The impacts of agrarian habitat types representative of the Northeast German Lowland
(cereal fields, fallows, meadows) on the structure of the spider assemblage have been
investigated on 16 study sites in the biosphere reserve Schorfheide-Chorin (Brandenburg,
Germany). During 3 years (1995-1997) epigeal spiders were collected by pitfall traps
(PT: n=8/10) and ground photo-eclectors (GPE: n=6).
Altogether 40536 specimens belonging to 179 species were recorded, among them several taxa (18%) listed in the Red Data Book of Germany (n=29) and of Brandenburg (n=21). The highest biodiversity was recorded for pastures with 108/97 species (according to PT/GPE catches), followed by fallows (101/89) and fields (78/69). Within arable land most species were recorded on a biodynamic cereal field cultivated after a four-year period of fallow. Using estimates of niche width, Porrhomma microphthalmum, Erigone atra, Erigone dentipalpis, Savignia frontata and Meioneta rurestris were identified as characteristic species of cereal fields. Pelecopsis parallela, Oedothorax retusus, Trochosa ruricola and Alopecosa barbipes were characteristic of fallows and Thanatus arenarius, Trichopterna cito and Zelotes electus were typical of pastures. Only four species (Erigone atra, Meioneta rurestris, Pachygnatha degeeri, Pardosa palustris) were recorded on all study sites. Generally, most specimens and the highest activity biomass of spiders were manifested on grasslands and long-term fallows; the lowest levels were recorded for cereal fields. Fallowing of cereal fields seemed to promote the relative abundance and activity biomass of the spider assemblage immediately after taking the fields out of cultivation, whereas species diversity took longer to build up. A similar effect was obvious in cereal fields with a cultivation cycle that was interrupted by a one-year period of set aside. The dominance structure of the spider assemblage was clearly affected by the agrarian habitat types: While the relative abundance of linyphiid spiders increased from meadows to cereal fields, the dominance position of lycosids decreased in the same sequence of agrarian habitat types. As expected, diversity indices using estimates of alpha (log series) were lowest on cereal fields, and highest on extensively used pastures as well as long-term fallows, independent of the sampling method.
Department of Zoology, Vilnius University, Ciurlionio str. 21/27, LT 2009 Vilnius, Lithuania. E-mail: email@example.com
Relys V.: Arctic-alpine and boreo-montane spider species (Araneae) in epigeic spider communities in the subalpine zone of the Eastern Alps. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 227-234.
Epigeic spider communities from 57 localities situated at altitudes of 1500 m up to 2300 m were analysed with the aim of evaluating any impact of arctic-alpine and boreo-montane spider species on these communities. 27 spider species having such disjunct distribution patterns were found. In 14 subalpine localities no species from both groups were found. Proportions of these groups in the communities were remarkably lower than of the alpine- endemic species. Boreo-montane species were not numerous. In most cases they made up 1- 2%, rarely 3%, of all collected specimens. Most arctic-alpine species have a centre of distribution in the alpine zone, only few were well represented in high subalpine localities. In high subalpine communities more than 15% of species and 10% of specimens can belong to arctic-alpine species. Only two arctic-alpine species (Meioneta gulosa and Oreonetides vaginatus) and one boreo-montane species (Micaria aenea) regularly spread to lower zones and habitats. Ecology and Ronal distribution were rather atypical for the arctic-alpine species Collinsia nemenziana Thaler.
Institute of Entomology, Czech Academy of Sciences, Braniovská 31, 370 05 České Budějovice, Czech Republic. E-mail: firstname.lastname@example.org
Růička V.: Spiders (Araneae) of two valleys in the Krkonoe Mts. (Czech Republic). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 235-244.
Spiders of three localities in the Krkonoe Mts. were studied: a) east-facing exposed rock walls in the Labský Důl valley, 1000 m a.s.l., b) west-facing exposed small rocks in the Obří Důl valley on the slope of Sněka Mt., 1500 m a.s.l., c) the bottom of the Obří Důl valley with a rich herb vegetation, 1000 m a.s.l. Leeward rock walls exhibited a higher species diversity than windward rocks. Tall herb vegetation in a leeward site of a corrie exhibited a higher species diversity than short herb vegetation on the mountain summits. Notes are given on the presence of Diplocentria bidentata, Lepthyphantes arciger, Meioneta milleri, and Micrargus georgescuae. Bolyphantes caucasicus represent new records for Central Europe, Maro lehtineni for the Czech Republic.
Institute of Biology, University of Latvia, Miera iela 3, LV-2169, Salaspils, Latvia. Fax: +371-9-345 412. E-mail: email@example.com
Salmane I.: Investigation of the seasonal dynamics of soil Gamasina mites (Acari: Mesostigmata) in Pinaceum myrtilosum, Latvia. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 245-252.
Investigation was made because of the lack of data on soil Gamasina mite seasonal dynamics in coniferous forests of Latvia and their relation to the changes of soil ecological conditions during the season. Investigations were carried out on the seasonal dynamics of some soil microarthropod groups, numbers of Gamasina species and individuals, and species diversity, in relation to soil ecological conditions. Soil microarthropods, including Gamasina mites, were shown to depend on soil ecological conditions. The soil relative humidity must be recognised as a limiting factor. It was found that when there is enough humidity, the decisive factor is soil temperature.
Bernhard SCHERABON, Benjamin GANTENBEIN, Victor FET, Mark BARKER, Matjaz KUNTNER,
Christian KROPF, Dietmar HUBER
Liebenauer Hauptstrasse 93, A-8041 Graz, Austria
Institute of Zoology, Division of Population Biology, University of Berne, Baltzerstrasse 3, CH-3012 Berne, Switzerland. Fax: +41 31 631 48 88. E-mail: firstname.lastname@example.org,
Department of Biological Sciences, Marshall University, Huntington, West Virginia 25755-2510, USA.
Department of Biological Sciences, George Washington University, Washington, D.C. 20052, USA; Institute of Biology, Centre for Scientific Research of the Slovenian Academy of Sciences and Arts, Novi Trg 5, SI-1000 Ljubljana, Slovenia.
Natural History Museum Berne, Bernastrasse 15, CH-3005 Berne, Switzerland.
P.O. Box 27, A-6811 Göfis, Austria.
Scherabon B., Gantenbein B., Fet V., Barker M., Kuntner M., Kropf C., Huber D.: A new species of scorpion from Austria, Italy, Slovenia and Croatia: Euscorpius gamma Caporiacco, 1950, stat. nov. (Scorpiones: Euscorpiidae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 253-262.
Scherabon (1987) recorded for the Austrian fauna two separate forms under Euscorpius germanus (C. L. Koch), a so-called typical (T-Form) from Tyrol and Carinthia, and a Karawanken-Form (K-Form) limited to southern Carinthia. New morphological data on animals collected in Carinthia, Italy and Slovenia, as well as genetic analyses (allozymes and mitochondrial DNA), show that the so-called K-Form is in fact a separate species belonging to the Euscorpius mingrelicus complex, a phylogenetic lineage distinct from E. germanus (C. L. Koch). The correct name for this species is E. gamma Caporiacco, 1950, stat. nov. (=E. germanus histrorum Caporiacco, 1950). It was described from northeastern Italy and the adjacent territory of Slovenia as a subspecies of E. germanus; we fix a lectotype of this species from the Risano (now Rizana) River in northern Istria, Slovenia. E. gamma is also found in Croatia. A number of other forms of the E. mingrelicus complex are found in the Balkans and Anatolia; their status is still unclear. We also fix a neotype of Euscorpius mingrelicus (Kessler, 1874) from Batumi, Georgia (Caucasus).
Rowley Snazell, Ralph Clarke
Institute of Terrestrial Ecology, Furzebrook Research Station, Wareham, Dorset, BH20 5AS, United Kingdom.
Snazell R., Clarke R.: The colonisation of an area of restored chalk downland by spiders (Araneae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 263-271.
Changes in both the plant and spider communities have been recorded on a 1.5 hectare area of restored downland that was previously arable. The restoration involved the relocation of turf of both high and lower species diversity from the route of the new road using a newly developed technique, and three different seed mixes. Both pitfall trapping and D-Vac sampling have been used, but only the pitfall trap data is used here. The spider data used is from 14 109 individuals representing 65 species. Sampling and botanical survey were carried out in 1993-1996 and 1998, and will be repeated in 2000 and 2002. As the downland sward has developed and the amount of bare ground has decreased there has been a rapid decrease in the number of highly mobile, early colonising species which is mirrored by rapid increase in cursorial species. The latter have already reached a peak and are now declining to numbers more typical of mature downland. The spider communities on the different treatments in each year have been analysed using CANOCO. This shows how the five communities have changed and converged over the six year period.
Department of Zoology, University of Aarhus, Building 135, DK-8000 Arhus C, Denmark. E-mail: email@example.com
Toft S.: Species and age effects in the value of cereal aphids as food for a spider (Araneae). In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 273-278.
All three species of aphids from cereal crops, Rhopalosiphum padi, Sitobion avenae and Metopolophium dirhodum were low quality prey for hatchlings of the wolf spider Pardosa prativaga, as revealed by development, growth and survival of the spider when the aphids were given as single-species diets. The species differed in food value, however, with M. dirhodum of highest value, S. avenae intermediate, and R. padi the lowest value. The latter species was no better than starvation. Spiderlings on a mixed diet of all three aphids showed intermediate performance, indicating that they were unable to select optimally among the prey available. Small juvenile instars of R. padi were of higher value as food than mature females. This result was predicted from life-history theory on the assumption that low food value is associated with a costly (chemical) defence against predators.
Szent István University, Faculty of Agricultural and Environmental Sciences, Department of Plant Protection, Páter K. u. 1., H-2103 Gödöllő, Hungary. E-mail: firstname.lastname@example.org
Tóth F.: Aspirator gun a new device for sampling spiders and insects. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 279-280.
Jakob E. Walter
Rheinfallquai, CH-8212 Neuhausen, Switzerland. E-mail: email@example.com
Walter J.E.: A look at arachnology in the 18th century. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 281-282.
Grażyna Wilczek, Agnieszka Babczyńska
Department of Human and Animal Physiology, The University of Silesia, Bankowa 9, 40-007 Katowice, Poland.
Wilczek G., Babczyńska A.: Heavy metals in the gonads and hepatopancreas of spiders (Araneae) from variously polluted areas. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 283-292.
Spiders, as secondary consumers, ingest considerable amounts of various xenobiotics,
including heavy metals. The amounts of ingested metals depends on hunting activity of the
spider and on the body composition of their prey. On the other hand, specificity of metal
excretion and storage in intracellular granules, rather than the quality of food, is
responsible for their high metal body burden. The aim of this study was to determine
whether heavy metal levels in the gonads and hepatopancreas of selected spiders species
would reflect their adaptability to environmental pollutants in relation to their
physiological and behavioural specificity. Contents of CD, Pb, Cu and Zn were measured by
means of flameless and flame AAS in females of 6 species: Araneus diadematus, Araneus
marmoreus (Araneidae), Metellina segmentata (Metidae), Linyphia triangularis
(Linyphiidae), Pardosa amentata (Lycosidae) and Agelena labyrinthica
(Agelenidae). The material was collected at two sites which differ in the level of
industrial pollutants, including heavy metals: Łosień (near Katowice steelworks
heavily polluted environment) and Brenna-Bukowa in Beskid lšski Mountains (reference
Heavy metal levels in the analysed organs did not reflect the metal content in the predators biotopes. Nevertheless, Cd, Pb and Zn levels in the hepatopancreas were always higher than in the gonads, irrespective of the site from which the spiders had been collected. This may suggest that midgut glands of the predators are an efficient barrier for these elements, protecting other organs, including gonads, against the toxicity of heavy metals.
Heavy metal concentrations in spiders tissues appeared, however, species-dependent, and this might be influenced by both behavioural and physiological methods of inactivation of heavy metals in different tissues. Among the web building spiders, L. triangularis seems to be the most efficient regulator of heavy metals in the tissues as was indicated by a significantly lower concentration of these xenobiotics in comparison with the other species in both of the tissues investigated. On the other hand, the wandering P. amentata and the web-building M. segmentata probably store all the heavy metals ingested with their food as mineral concentrations, mainly in cells of the hepatopancreas.
Marek Żabka, Wolfgang Nentwig
Katedra Zoologii WSRP, 08-110 Siedlce, Poland. E-mail: firstname.lastname@example.org
Zoological Institute, University of Berne, Baltzerstrasse 3, 3012 Bern, Switzerland. E-mail: email@example.com
Żabka M.M., Nentwig W.: Salticidae (Arachnida: Araneae) of the Krakatau Islands (Indonesia) a preliminary approach. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 293-306.
The salticid fauna of the Krakatau Islands is investigated in respect to species composition, immigration, colonisation-extinction rates and relationships with adjacent areas. The changes in fauna of Panjang between 1931 and 1991 are discussed and the salticids of other islands of the archipelago are studied. Of 33 species known from the area in 1984-91, 22 are listed from Anak Krakatau, 19 from Rakata, 14 from Panjang and 12 from Sertung.
Samuel Zschokke, Fritz Vollrath
Department of Zoology, South Parks Road, Oxford OX1 3PS, United Kingdom.
Zoologisches Institut, Universität Basel, Rheinsprung 9, CH4051 Basel, Switzerland.
Institut für Natur-, Landschafts- und Umweltschutz, Universität Basel, St. Johanns-Vorstadt 10, CH-4056 Basel, Switzerland. Fax: +41 61 267 08 32. E-mail: firstname.lastname@example.org
Department of Zoology, Universitetsparken B135, DK8000 Aarhus C, Denmark.
Zschokke S., Vollrath F.: Planarity and size of orb-webs built by Araneus diadematus (Araneae: Araneidae) under natural and experimental conditions. In Gajdo P., Pekár S. (eds): Proceedings of the 18th European Colloquium of Arachnology, Stará Lesná, 1999. Ekológia (Bratislava), Vol. 19, Supplement 3/2000, p. 307-318.
Orb-weaving spiders build more or less planar webs in a complex, three dimensional environment. How do they achieve this? Do they explore all twigs and branches in their surroundings and store the information in some form of mental map? Or do they at first just build a cheap (i.e. few loops, possibly non-planar) web to test the site and if this first web is successful (i.e. the web site is good) later build subsequent improved and enlarged webs, by re-using some of the anchor points and moving other anchor points? The second hypothesis is supported by the fact that the garden cross spider Araneus diadematus Clerck (Araneidae) usually builds several webs at the same site, re-using structural parts of one web for subsequent webs. To further test the second hypothesis, we measured and assessed the planarity of first and of subsequent webs built in the field and in the laboratory.