Haltung und Zucht der Geißelspinne (Damon variegatus) (Phrynichidae) (Chelicerata: Amblypygi)

In the temporary carboniferous hall of „GONDWANA - Das Prähistorium“ in Germany, whip spiders (Damon variegatus) were kept and bred. 3,3 were purchased from a dealer in summer 2007. The night active spiders were kept together in a terrarium. No aggresions were observed. The animals were fed little locusts, young hissing cockroaches, and crickets. In 2008 courtship display and mating could be observed. The biggest male was the only active one. After 7 days after the intake of the spermatophores all females carried eggsacs under the ophistosoma. Each egg sack contained approximately 25-30 eggs. During the carrying phase only one female feasted on a cricket. 98 days after the egg sack was produced the young spiderlings hatched. The coloration of the spiderlings was completely different from the coloration of the adults. The spiderlings were carried by the female for the next 9 days. Then, the spiderlings moulted and left the female immediately. The adults were now separated from their young. The three groups of spiderlings stayed together in a smaller terrarium. However, each group from each female stayed separate from the others for weeks. The second moulting took place 41 days after the first one. No cannibalism was observed. Obviously Damon variegatus seems to be a spider with a social touch. If the terrarium and the climate conditions inside are adapted to the needs of the whip spiders keeping and breeding is possible. The species is highly attractive to visitors.     

Side-effects of insecticides on two erigonid spider species

The current rearing technique forErigone atra (Blackwall) andOedothorax apicatus (Blackwall) (Araneae, Erigonidae) was improved. To reduce time spent rearing on live fruit flies the spiders were kept on a culture of the Collembola speciesLepidocyrtus lanuginosus (Gmelin) (Entomobryidae). Side-effects on spiders of two pyrethroid insecticides (fenvalerate and lambda-cyhalothrin) and one carbamate insecticide (pirimicarb) were tested. Sensitivity of adults of both sexes and juveniles to insecticides and their influence on the rate of emergence of spiderlings from cocoons were investigated using topical application, spraying or residual contact. LD₅₀ values for adults ranged from 0.49 to 2.52 ng a.i./spider for lambda-cyhalothrin and from 5.75 to 98.20 ng a.i./spider for fenvalerate. Topical application also resulted in up to a week's delay of web-building. A moving laboratory spraying equipment was used to spray spiders with different insecticide dosages and water volumes. Pyrethroids sprayed onto adults in webs had stronger effects than pyrethroids sprayed onto sitting or walking spiders on the soil surface. Residual contamination caused higher mortality of spiders after contact with lambda-cyhalothrin than fenvalerate. In all tests, males were more susceptible to pyrethroids than females; this difference was related to body weight. Mortality rate was higher forE. atra than forO. apicatus. Both pyrethroids were also toxic to spiderlings. Lambda-cyhalothrin inhibited emergence ofE. atra spiderlings from cocoons. Pirimicarb was harmless to both spider species.     

Interactions among young stages of the wolf spiders Pardosamoesta and P. mackenziana (Araneae: Lycosidae)

Young stages of the wolf spiders Pardosa moesta and P . mackenziana coexist on the forest floor in a deciduous forest in central Alberta, yet nothing is known of the potential interactions between and among these ubiquitous species. An experiment, using a series of 0.25-m² arenas, was designed to test for inter- and intraspecific exploitative competition. Experimental treatments were established in the arenas in late July. Treatments involved stocking recently hatched spiderlings of each species alone, and with both species together at natural (10 spiderlings per arena) and two times the natural densities. In September the arenas were searched for Pardosa spiderlings, and the survival and mass gain of each species were determined. Other predatory arthropods, and Collembola, a common prey of young wolf spiders, were counted in the arenas before the experimental treatments were established and at the end of the experiment. No evidence for competitive interactions was uncovered, but spiderling survival was 29% for P . moesta and 20% for P . mackenziana , suggesting other mortality factors (e.g., cannibalism, intraguild predation) may be important. Top-down effects (predatory arthropods) had no effect on Pardosa survival. Bottom-up effects, however, were significant as treatments containing spiderlings had fewer Collembola compared to control arenas, further supporting the importance of spiders in leaf-litter food webs.     

The value of two Collembola species as food for a linyphiid spider

Egg production by the cereal spider Erigone atra was used as a fitness parameter for evaluating the food quality of two species of Collembola: Folsomia fimetaria and Isotoma anglicana. Drosophila melanogaster was used as reference prey. We tested the hypothesis that due to differences in food quality, the two Collembola species would affect the reproduction of the spider differently. The quality ranking of the prey types turned out as: I. anglicana > D. melanogaster > F. fimetaria. With F. fimetaria alone, spiders were unable to maintain reproduction. E. atra was more efficient in utilising I. anglicana and D. melanogaster. Thus, daily consumption rates of I. anglicana were lower in spite of higher egg laying rates by E. atra. A mixed diet of F. fimetaria and D. melanogaster resulted in a lower reproductive output than a pure diet of D. melanogaster, indicating a toxic element in F. fimetaria. In the mixed diet F. fimetaria had a negative influence on the consumption capacity of the spider towards D. melanogaster, while D. melanogaster had a positive influence on the consumption capacity towards F. fimetaria. It is concluded that a high abundance of I. anglicana may support a high reproductive output of E. atra, while the presence, of F. fimetaria in fields may reduce the spider's reproductive output.     

Haltung und Zucht der Geißelspinne (Damon variegatus) (Phrynichidae) (Chelicerata: Amblypygi)

In the temporary carboniferous hall of „GONDWANA – Das Prähistorium“ in Germany, whip spiders (Damon variegatus) were kept and bred. 3,3 were purchased from a dealer in summer 2007. The night active spiders were kept together in a terrarium. No aggresions were observed. The animals were fed little locusts, young hissing cockroaches, and crickets. In 2008 courtship display and mating could be observed. The biggest male was the only active one. After 7 days after the intake of the spermatophores all females carried eggsacs under the ophistosoma. Each egg sack contained approximately 25–30 eggs. During the carrying phase only one female feasted on a cricket. 98 days after the egg sack was produced the young spiderlings hatched. The coloration of the spiderlings was completely different from the coloration of the adults. The spiderlings were carried by the female for the next 9 days. Then, the spiderlings moulted and left the female immediately. The adults were now separated from their young. The three groups of spiderlings stayed together in a smaller terrarium. However, each group from each female stayed separate from the others for weeks. The second moulting took place 41 days after the first one. No cannibalism was observed. Obviously Damon variegatus seems to be a spider with a social touch. If the terrarium and the climate conditions inside are adapted to the needs of the whip spiders keeping and breeding is possible. The species is highly attractive to visitors.     

真水狼蛛幼蛛各龄期的形态特征和生长发育

幼蛛在蜘蛛的种群中占有很大比例。通过室内饲养。获得了不同龄期的真水狼蛛幼蛛。其体重、体长、背甲宽、步足长、眼域宽以及中斑下的条形纵斑长度都随着龄期的增大而增加。背甲宽和中斑下的条形斑纹长度可用来判断真水幼蛛的龄期。雌蛛的取食量大于雄蛛,高龄幼蛛大于低龄幼蛛。幼蛛在蜕皮时不取食,蜕皮后,取食量明显增加。     

Diet-Dependent Survival, Development and Fecundity of the Spider Atypena formosana (Oi) (Araneae: Linyphiidae)Implications for Biological Control in Rice

The development time of Atypena formosana was assessed on four different diets: (1) brown planthopper (BPH), Nilaparvata lugens ; (2) green leafhopper (GLH), Nephotettix virescens ; (3) Collembola (Entomobryidae); and (4) a mixed diet of Collembola, hoppers and Drosophila melanogaster . A starvation treatment served as a control. We tested the hypothesis that because of differences in food quality, the diets would affect survival and development differently. Survival differed significantly among the diets. No spiders survived until adult on the diet of GLH, only a single individual survived on the diet of BPH, whereas 70% survived until adult on the Collembola diet and all survived on the mixed diet. Development times were significantly different among the diets tested. Spiders developed fastest on the mixed diet and the Collembola diet. The biomass of prey consumed within 48 h and the total biomass of prey consumed to complete an instar were highest on the mixed diet. Finally the mixed diet resulted in higher fecundity than the Collembola diet. It is concluded that alternative prey are an absolute necessity, as BPH and GLH diets alone would not be able to increase the number of predators, regardless of the number of hoppers present.     

Survival strategies of the crab spider Thomisus onustus Walckenaer 1806 (Chelicerata,Arachnida, Thomisidae)

Summary The initial energy supply of emerging spiderlings is relatively meagre, so survival without feeding on insects during a spell of bad weather is limited to a period of a few days or weeks. During our investigations, spiderlings of Thomisus onustus (Arachnida, Thomisidae) were kept on different diets. There was a significant difference in survival rate between spiderlings that were starved or fed on pollen, nectar, or Drosophila. The results showed that pollen and nectar can be a source of energy for spiders for an extensive period. This demonstrates another way in which spiders may survive starvation when insect prey is lacking and thus ensure the survival of a whole population.     

Influence of prey availability and conspecifics on patch quality for a cannibalistic forager: laboratory experiments with the wolf spider Schizocosa

 Because cannibals are potentially both predator and prey, the presence of conspecifics and alternative prey may act together to influence the rate at which cannibals prey upon each other or emigrate from a habitat patch. Wolf spiders (Lycosidae) are cannibalistic-generalist predators that hunt for prey with a sit-and-wait strategy characterized by changes in foraging site. Little information is available on how both prey abundance and the presence of conspecifics influence patch quality for these cursorial, non-web-building spiders. To address this question, laboratory experiments were conducted with spiderlings and older juveniles of the lycosid genus Schizocosa. The presence of insect prey consistently reduced rates of spider emigration when spiders were housed either alone or in groups. Solitary juvenile Schizocosa that had been recently collected from the field exhibited a median giving-up time (GUT) of 10 h in the absence of prey (Collembola); providing Collembola increased the median GUT to 64 h. For solitary spiders, the absence of prey increased by about fourfold the rate of emigration during the first 24 h. In contrast, for spiders in patches with a high density of conspecifics, the absence of prey increased the 24-h emigration rate by only 1.6-fold. For successful cannibals in the no-prey patches, the presence of conspecifics improved patch quality by providing a source of food. Mortality by cannibalism was affected by both prey availability and openness of the patch to net emigration. In patches with no net emigration, the presence of prey reduced rates of cannibalism from 79% to 57%. Spiders in patches open to emigration but not immigration experienced a rate of cannibalism (16%) that was independent of prey availability. The results of these experiments indicate that for a cannibalistic forager such as the wolf spider Schizocosa, (1) the presence of conspecifics can improve average patch quality when prey are absent, and (2) cannibalism has the potential to be a significant mortality factor under natural field conditions because cannibalism persisted in prey patches that were open to emigration. Received: 12 April 1996 / Accepted: 14 August 1996     

The allometry of CNS size and consequences of miniaturization in orb-weaving and cleptoparasitic spiders

Allometric studies of the gross neuroanatomy of adults from nine species of spiders from six web-weaving families (Orbicularia), and nymphs from six of these species, show that very small spiders resemble other small animals in having disproportionately larger central nervous systems (CNSs) relative to body mass when compared with large-bodied forms. Small spiderlings and minute adult spiders have similar relative CNS volumes. The relatively large CNS of a very small spider occupies up to 78% of the cephalothorax volume. The CNSs of very small spiders extend into their coxae, occupying as much as 26% of the profile area of the coxae of an Anapisona simoni spiderling (body mass < 0.005 mg). Such modifications occur both in species with minute adults, and in tiny spiderlings of species with large-bodied adults. In at least one such species, Leucauge mariana, the CNS of the spiderling extends into a prominent ventral bulge of the sternum. Tiny spiders also have reduced neuronal cell body diameters. The adults of nearly all orbicularian spiders weave prey capture webs, as do the spiderlings, beginning with second instar nymphs. Comparable allometric relations occur in adults of both orb-weaving and cleptoparasitic species, indicating that this behavioral difference is not reflected in differences in gross CNS allometry.     

Artificial nest site preferences of Black-capped Chickadees

ABSTRACT.   To facilitate study of the breeding biology of parids, Grubb and Bronson (1995; Condor 97: 1067–1070) designed artificial "snags" made from polyvinyl chloride (PVC) tubes. Because the cost of artificial snags is greater than that of traditional wooden boxes, we examined alternatives to PVC snags for attracting chickadees to artificial nesting sites. From 2005 to 2007, we compared the use of PVC snags and wooden nest boxes by Black-capped Chickadees ( Poecile atricapillus ) in Sapsucker Woods Sanctuary in Ithaca, New York. We also quantified the use of cavities with and without wood shavings. The probability of chickadee excavation was greater (60–70% per yr) in filled snags (with wood shavings) than in filled boxes (40–50%; logistic mixed model, P = 0.01), and chickadees initiated more nests in filled snags (25–30%) than filled boxes (15%; P = 0.03). Chickadees also initiated significantly more nests ( P = 0.03) in filled than unfilled boxes. Although wooden boxes filled with wood shavings were used more often by Black-capped Chickadees than unfilled wooden boxes, artificial snags filled with wood shavings were used most, were no more likely than boxes to be usurped by House Wrens ( Troglodytes aedon ), and were less likely than boxes to be occupied by mice. Thus, artificial snags may be the better option for investigators studying the breeding biology of chickadees.     

Costs and benefits of facultative aggregating behaviour in the orb-spinning spider Gasteracantha minax Thorell (Araneae: Araneidae)

Abstract The potential costs and benefits of foraging in aggregations are examined for the orb-spinning spider Gasteracantha minax. Web-site tenacity is low in this species; individuals frequently move among sites, thereby joining aggregations of different sizes. Female spiders in aggregations suffered lower predation rates and attracted more males than their solitary counterparts. However, aggregated eggsacs, probably produced by females in aggregations, experienced higher rates of parasitism than solitary eggsacs. We found no evidence of higher prey capture success rates among spiders in aggregations. However, we demonstrate a novel way in which spiders can increase their foraging efficiency by decreasing silk investment. A spider spinning a web within an existing aggregation can attach the support threads of its web to those of other webs, thereby exploiting the silk produced by other spiders.     

An order-specific monoclonal antibody to Diptera reveals the impact of alternative prey on spider feeding behavior in a complex food web

Generalist predators have the capacity to restrict pest population growth, especially early in the season before densities increase. However, their polyphagous feeding habits sometimes translate into reduced pest consumption when they target alternative prey. An order-specific monoclonal antibody was developed to examine the strength of trophic connections between Diptera, a major category of non-pest prey, and linyphiid spiders in alfalfa. We report the development and characterization of a monoclonal antibody with order-level specificity to Diptera. This antibody elicited strong absorbance to 22 Diptera from 13 families, no false-positive reactivity to non-dipteran invertebrates, and antigen detection periods following prey consumption that were comparable between spiders. Over 900 field-collected females of the linyphiid spiders Erigone autumnalis and Bathyphantes pallidus were screened for Diptera antigen. Significantly more B. pallidus screened positive for Diptera (40%) compared to E. autumnalis (16%), indicating differential reliance on these prey. In parallel with the collection of spiders for gut-content analysis, prey availability was estimated at web sites. The two spiders exhibited different feeding responses to prey availability. Consumption of Diptera by B. pallidus was strongly correlated with Diptera abundance whilst the availability of other potential prey did not influence predation rates. Conversely, E. autumnalis did not prey upon Diptera in proportion to availability, but increased Collembola activity-density reduced dipteran consumption. Integration of molecular gut-content analysis with precise sampling of prey demonstrated how two closely related linyphiid spiders exhibit different feeding responses to the availability of prey under natural field conditions. Elucidating the feeding preferences of natural enemies is critical to effective incorporation of biological control by generalist predators in the management of agricultural pests.     

The effect of food deprivation on aeronautic dispersal behaviour (ballooning) inErigone spp. spiders

Adult male and femaleErigone spp. (Araneae: Linyphiidae) spiders were kept without food for several days. Groups of spiders were tested for aeronautic dispersal behaviour (ballooning) in the laboratory. The validity of the assessment method was tested. In comparison with satiated spiders, the starved group exhibited an increased tendency to engage in aeronautic dispersal behaviour. A consistent trend for increased dispersal behaviour was detected in three independent experiments. Implications for spiders in agro-ecosystems are discussed briefly.     

Invertebrate biodiversity affects predator fitness and hence potential to control pests in crops

Natural enemies that control pests usually allow farmers to avoid, or reduce, the use of pesticides. However, modern farming practices, that maximize yields, are resulting in loss of biodiversity, particularly prey diversity. Does this matter? Pests continue to thrive, and without alternative prey the predators should, perforce, concentrate their attentions upon the pests.We showed that a diverse diet significantly enhances predator fecundity and survival. Experiments were conducted using common generalist predators found in arable fields in Europe, the carabid beetle Pterostichus melanarius (Coleoptera: Carabidae) and the linyphiid spider Erigone atra (Araneae: Linyphiidae). We tested the hypothesis that mixed species diets were optimal, compared with restricted diets, with respect to parameters such as predator weights, egg weights, numbers of eggs laid, egg development times, egg hatching rates and predator survival. In carabids, an exclusive earthworm diet was as good as mixed diets containing earthworms for egg production and hatching, but less good than such mixed diets for increase in beetle mass and sustained egg laying. For spiders, aphids alone (Sitobion avenae) or with the Collembola Folsomia candida, drastically reduced survival. Aphids plus the Collembola Isotoma anglicana improved survival but only aphids with a mixed Collembola diet maximized numbers of hatching eggs.Predators offered only pests (slugs or aphids) had lowest growth rates and fecundity. We therefore demonstrated that conservation of a diversity of prey species within farmland, allowing predators to exploit a diverse diet, is essential if predators are to continue to thrive in crops and regulate agricultural pests.     

Invertebrate biodiversity affects predator fitness and hence potential to control pests in crops

Natural enemies that control pests usually allow farmers to avoid, or reduce, the use of pesticides. However, modern farming practices, that maximize yields, are resulting in loss of biodiversity, particularly prey diversity. Does this matter? Pests continue to thrive, and without alternative prey the predators should, perforce, concentrate their attentions upon the pests.We showed that a diverse diet significantly enhances predator fecundity and survival. Experiments were conducted using common generalist predators found in arable fields in Europe, the carabid beetle Pterostichus melanarius (Coleoptera: Carabidae) and the linyphiid spider Erigone atra (Araneae: Linyphiidae). We tested the hypothesis that mixed species diets were optimal, compared with restricted diets, with respect to parameters such as predator weights, egg weights, numbers of eggs laid, egg development times, egg hatching rates and predator survival. In carabids, an exclusive earthworm diet was as good as mixed diets containing earthworms for egg production and hatching, but less good than such mixed diets for increase in beetle mass and sustained egg laying. For spiders, aphids alone (Sitobion avenae) or with the Collembola Folsomia candida, drastically reduced survival. Aphids plus the Collembola Isotoma anglicana improved survival but only aphids with a mixed Collembola diet maximized numbers of hatching eggs.Predators offered only pests (slugs or aphids) had lowest growth rates and fecundity. We therefore demonstrated that conservation of a diversity of prey species within farmland, allowing predators to exploit a diverse diet, is essential if predators are to continue to thrive in crops and regulate agricultural pests.     

Cues for web invasion and aggressive mimicry signalling in Portia (Araneae, Salticidae)

Portia is a web-invading araneophagic spider that uses aggressive mimicry to deceive its prey. The present paper is a first step toward clarifying experimentally the cues that govern Portia's decisions of whether to enter a web, whether to make signals once in a web, and whether to persist at signalling once started. The following conclusions are supported: cues from seeing a web elicit web entry, but volatile chemical cues from webs of prey spiders are not important; seeing a spider in a web increases Portia's inclination to enter the web; after web entry, cues from webs of prey spiders are sufficient to elicit signalling behaviour, even in the absence of other cues coming directly from the prey spider; seeing a prey spider or detecting vibrations on the web make Portia more prone to signal, but volatile chemical cues from prey spiders are not important; once Portia is on a web and signalling, seeing a moving spider and detecting vibrations on the web encourage Portia to persist in signalling; on the basis of visual cues alone, Portia can distinguish between quiescent spiders, insects and eggsacs.     

Development, growth, and egg production of Ageneotettix deorum (Orthoptera: Acrididae) in response to spider predation risk and elevated resource quality

Abstract.  1. Predation risk to insects is often size- or stage-selective and usually decreases as prey grow. Any factor, such as food quality, that accelerates developmental and growth rates is likely to reduce the period over which prey are susceptible to size-dependent predation.
2. Using field experiments, several hypotheses that assess growth, development, and egg production rates of the rangeland grasshopper Ageneotettix deorum (Scudder) were tested in response to combinations of food quality and predation risk from wolf spiders to investigate performance variation manifested through a behaviourally mediated path affecting food ingestion rates.
3. Grasshoppers with nutritionally superior food completed development ≈ 8–18% faster and grew 15–45% larger in the absence of spiders, in comparison with those subjected to low quality food exposed to spider predators. Growth and development did not differ for grasshoppers feeding on high quality food when predators were present in comparison with lower quality food unimpeded by predators. Responses indicated a compensatory relationship between resource quality and predation risk.
4. Surviving grasshoppers produced fewer eggs compared with individuals not exposed to spiders. Because no differences were found in daily egg production rate regardless of predation treatment, lower egg production was attributed to delayed age of first reproduction. Results compare favourably with responses observed in natural populations.
5. Risk of predation from spiders greatly reduced growth, development, and ultimately egg production. Increased food quality counteracts the impact of predation risk on grasshoppers through compensatory responses, suggesting that bottom-up factors mediate effects of spiders.     

Evaluation of lycosid,micryphantid and linyphiid spiders as predators ofRhopalosiphum padi (Hom.: Aphididae) and their functional response to prey density-laboratory experiments

Laboratory experiments were performed to determine the potential of dominant spider species in winter wheat in Germany,Erigone atra (Blackwall),Lepthyphantes tenuis (Blackwall) andPardosa agrestis (Westring) adults and youngs, in suppressing the population ofRhopalosiphum padi (L.) on wheat plants and their functional response to different aphid densities. The presence of spiders significantly caused between 34 and 58% reduction in aphid population development on wheat plants compared to the aphid population in the absence of spiders. The functional response curves for these spiders as predators ofR. padi seem to descrive a typical type II functional response with the prey consumed increasing to a plateau as aphid densities increased. Prey killed without eating was linear on prey density.     

The impact of altered precipitation on spatial stratification and activity-densities of springtails (Collembola) and spiders (Araneae)

Abstract.  1. A field experiment was conducted to determine how short-term changes in moisture can alter activity-densities of spiders and springtails.
2. In a Kentucky forest 10 unfenced 4-m² plots were divided into two rainfall treatments. A clear roof over five plots excluded rainfall to simulate severe drought conditions ( drought treatment). Water was sprayed on the five uncovered plots at a rate equal to two times the long-term mean in order to establish the high-rainfall treatment. Activity-densities of Collembola and spiders were measured using pitfall traps designed to sample the top, middle, and bottom layers of leaf litter. The experiment ran from 20 July to 23 September 2001.
3. Overall (i.e. litter layers pooled) activity-density (mean number trapped each sampling date) of Collembola was ≈ 60% lower in drought plots than in plots receiving increased precipitation. Surprisingly, overall spider activity-density was ≈ 1.6 times greater in the drought plots.
4. Differences in rainfall affected the spatial stratification of Collembola and spiders in strikingly different ways. Activity-densities of neither group differed between drought and high-rainfall treatments in the bottom litter layer. Collembola activity-density was three times greater in the top and middle litter layers in high-rainfall plots than in drought plots. In contrast, spider activity-density did not differ between treatments in the top layer, but activity-density was decreased by 50% in the middle layer of high-rainfall plots compared with drought plots.
5. Three Collembola families (Sminthuridae, Tomoceridae, and Entomobryidae) accounted for most of the Collembola pattern. The spider response was due to altered activity-density of one family of wandering spider, the Gnaphosidae.