An orb‐weaver spider exploits an ant–acacia mutualism for enemy‐free space

Exploiters of protection mutualisms are assumed to represent an important threat for the stability of those mutualisms, but empirical evidence for the commonness or relevance of exploiters is limited. Here, I describe results from a manipulative study showing that an orb‐weaver spider, Eustala oblonga, inhabits an ant‐acacia for protection from predators. This spider is unique in the orb‐weaver family in that it associates closely with both a specific host plant and ants. I tested the protective effect of acacia ants on E. oblonga by comparing spider abundance over time on acacias with ants and on acacias from which entire ant colonies were experimentally removed. Both juvenile and adult spider abundance significantly decreased over time on acacias without ants. Concomitantly, the combined abundance of potential spider predators increased over time on acacias without ants. These results suggest that ant protection of the ant‐acacia Acacia melanocerus also protects the spiders, thus supporting the hypothesis that E. oblonga exploits the ant–acacia mutualism for enemy‐free space. Although E. oblonga takes advantage of the protection services of ants, it likely exacts little to no cost and should not threaten the stability of the ant–acacia mutualism. Indeed, the potential threat of exploiter species to protection mutualisms in general may be limited to species that exploit the material rewards traded in such mutualisms rather than the protection services.     

Evidence of exploitative competition among young stages of the wolf spider Schizocosa ocreata

Summary Previous research by many investigators has demonstrated food limitation in both web-building and wandering spiders. Field experiments have tested for exploitative competition for prey in web-building, but not wandering species. As a first step to examining the question of whether spiders without webs exhibit exploitative competition, we manipulated densities of young stages of a common wolf spider, Schizocos ocreata, and measured (1) spider growth rate and (2) numbers of Collembola, a potential prey organism. Replicate populations of recently hatched S. ocreata were established in 1-m² fenced plots at four levels: 0×, 0.25×, 1× and 4× natural density. Increasing spider density had a negative effect on spider growth rate, defined as increase in weight or cephalothorax width. Early in the experiment spider density had a weak negative effect on Collembola numbers [p(F)=0.08]. Taken together, this probable response by Collembola and the clear effect of spider density on growth rate constitute the first experimental evidence of intraspecific exploitative competition for prey in a species of wandering spider. We discuss (1) the strength of this evidence given the constraints of the experiment's design, and (2) the implications of the strong convergence in spider densities that had occurred after 2.5 months.     

Evaluation of airborne methyl salicylate for improved conservation biological control of two-spotted spider mite and hop aphid in Oregon hop yards

The use of synthetic herbivore-induced plant volatiles (HIPV) to attract natural enemies has received interest as a tool to enhance conservation biological control (CBC). Methyl salicylate (MeSA) is a HIPV that is attractive to several key predators of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and hop aphid, Phorodon humuli (Schrank) (Homoptera: Aphididae). A 2-year study was conducted to evaluate the recommended commercial use of MeSA in hop yards in Oregon. Slow-release MeSA dispensers were stapled to supporting poles in 0.5 ha plots and these plots were compared to a paired non-treated plot on each of three farms in 2008 and 2009. Across both years, there was a trend for reduced (range 40–91%) mean seasonal numbers of T. urticae in five of the six MeSA-baited plots. Stethorus spp., key spider mite predators, tended to be more numerous in MeSA-baited plots compared to control plots on a given farm. Mean seasonal densities of hop aphid and other natural enemies (e.g., Orius spp. and Anystis spp.) were similar between MeSA-treated and control plots. Variability among farms in suppression of two-spotted spider mites and attraction of Stethorus spp. suggests that the use of MeSA to enhance CBC of spider mites in commercial hop yards may be influenced by site-specific factors related to the agroecology of individual farms or seasonal effects that require further investigation. The current study also suggests that CBC of hop aphid with MeSA in this environment may be unsatisfactory.     

Consumption of Habenaria sagittifera pollinia by juveniles of the katydid Ducetia japonica

While Habenaria (Orchidaceae) is a species‐rich genus and the orchid diversification is considered to be tightly related to its diverse pollination system, floral visitors of few Habenaria spp. have been studied. Here, we investigated the diurnal floral visitors of Habenaria sagittifera. While Orthoptera have not been considered a regular floral visitor, we observed that juvenile katydid Ducetia japonica (Tettigoniidae) regularly visited and consumed the pollinia and anther caps of H. sagittifera. The relationship between Habenaria and Ducetia would not be a tight mutualism. However, the regular visitation and pollinia consumption may showcase the evolutionary route to Orthoptera–orchid pollination mutualism.     

Impact of transgenic Bacillus thuringiensis cotton on a non-target pest Tetranychus spp. in northern China

Field studies were carried out to evaluate the effect of two transgenic cotton varieties (SGK321 carrying Cry1A+CpTI and DP99B carrying Cry1Ac) and the conventional variety (shiyuan321‐parental line of SGK321) on spider mites, Tetranychus spp. from 2002 to 2004. In 2002, this experiment included three treatments: Bt cotton field (SGK321) treated with acaricides against spider mites, untreated non‐Bt cotton field (Shiyuan321), and untreated Bt cotton field (SGK321). In 2003–2004, there are four types of treatments after a new transgenic Bt cotton variety, DP99B (non‐chemical control), was added into the experiments. The results showed that there were no significant difference in densities of spider mites among Bt without acaricides and non‐Bt without acaricides cotton fields, nor was there a significant difference in damage of spider mites to cotton among these treatments (P > 0.1). However, there are significant differences (P < 0.05) in densities of spider mites and damage caused by spider mites between cotton fields with and without acaricides. Acaricide significantly reduced the densities of spider mites in Bt cotton (P < 0.05). These results suggest that Bt cotton has no effect on spider mites populations. However, spider mites have the potential for severe damage in Bt cotton fields. Acaricides are essential tools in controlling cotton spider mites in northern China.     

Ontogeny of prey selection inSirthenea carinata: Generalist juveniles become specialist adults

Prey selection bySirthenea carinata (F.) [Hemiptera: Reduviidae] was investigated using both field captured and laboratory-reared nymphs and adults. Small nymphs (instars 1–3) showed no preference for mole crickets [Orthoptera: Gryllotalpidae: Scapteriscus] as prey overGryllus spp. orAnurogryllus muticus (De Geer) [Orthoptera: Gryllidae]. Larger nymphs (4th and 5th instars) and adults showed a significant preference for mole crickets in the same sort of choice experiments, choosing mole crickets 84% of the time. Laboratory hatchedSirthenea nymphs matured faster on a mixed diet ofGryllus spp.,A. muticus, andScapteriscus spp. Than did siblings fed a diet ofGryllus spp. alone, but no differences were found in size or duration of individual stadia between the diet groups.      

Regional patterns in the invasion success of <Emphasis Type="Italic">Cheiracanthium</Emphasis> spiders (Miturgidae) in vineyard ecosystems

Invasions have often been linked to reduced biodiversity, but the role of non-native species in the decline of native species is ambiguous. In a 2003 survey of four California vineyard regions, exotic spiders (Cheiracanthium spp.) were more dominant in vineyards with lower spider species diversity and reduced spider abundance. There was no evidence for the role of species interactions in the invasion of Cheiracanthium spiders, however, as native spiders from the same feeding guild were most abundant in regions with high Cheiracanthium levels. Comparison with a survey conducted 10 years earlier indicated that the recent invader C. mildei simply represented an addition to the spider community, with no apparent change in proportions of the congener C. inclusum. Invasion success is discussed with respect to agricultural habitat, as results suggest that disturbed conditions in many vineyards may favor Cheiracanthium spp. and native wandering spiders while decreasing overall spider diversity.     

The effect of colour variation in predators on the behaviour of pollinators: Australian crab spiders and native bees

1. Australian crab spiders exploit the plant–pollinator mutualism by reflecting UV light that attracts pollinators to the flowers where they sit. However, spider UV reflection seems to vary broadly within and between individuals and species, and we are still lacking any comparative studies of prey and/or predator behaviour towards spider colour variation. 2. Here we looked at the natural variation in the coloration of two species of Australian crab spiders, Thomisus spectabilis and Diaea evanida, collected from the field. Furthermore, we examined how two species of native bees responded to variation in colour contrast generated by spiders sitting in flowers compared with vacant flowers. We used data from a bee choice experiment with D. evanida spiders and Trigona carbonaria bees and also published data on T. spectabilis spiders and Austroplebeia australis bees. 3. In the field both spider species were always achromatically (from a distance) undetectable but chromatically (at closer range) detectable for bees. Experimentally, we showed species‐specific differences in bee behaviour towards particular spider colour variation: T. carbonaria bees did not show any preference for any colour contrasts generated by D. evanida spiders but A. australis bees were more likely to reject flowers with more contrasting T. spectabilis spiders. 4. Our study suggests that some of the spider colour variation that we encounter in the field may be partly explained by the spider's ability to adjust the reflectance properties of its colour relative to the behaviour of the species of prey available.     

Spatial variation in the strength of mutualism between a jumping spider and a terrestrial bromeliad: Evidence from the stable isotope N

Psecas chapoda, a neotropical jumping spider strictly associated with the terrestrial bromeliad Bromelia balansae in cerrados and semi-deciduous forests in South America, effectively contributes to plant nutrition and growth. In this study, our goal was to investigate if spider density caused spatial variations in the strength of this spider–plant mutualism. We found a positive significant relationship between spider density and δ¹⁵N values for bromeliad leaves in different forest fragments. Open grassland Bromeliads were associated with spiders and had higher δ¹⁵N values compared to forest bromeliads. Although forest bromeliads had no association with spiders their total N concentrations were higher. These results suggest that bromeliad nutrition is likely more litter-based in forests and more spider-based in open grasslands. This study is one of the few to show nutrient provisioning and conditionality in a spider–plant system.     

Non‐pollinating Fig Wasps Decrease Pollinator and Seed Production in Ficus andicola (Moraceae)

Fig trees ( Ficus spp.) and Agaonine fig‐wasps participate in an obligate mutualism. Fig wasps can only develop within fig inflorescences (syconia) and they are the only organisms capable of pollinating fig flowers. Other non‐pollinating wasps that lay eggs by inserting their ovipositors from the outside can also develop in syconia. These parasitic wasps may be parasitoids of either pollinating or other non‐pollinating wasps, or form galls in fig flowers or other tissues. Depending on this interaction, parasitic wasps may have various effects on the production of pollinating wasps and seeds. Wasps in the genus Idarnes, which parasitize New World figs (subgenus Urostigma), have an effect on wasp production but not on seed production. Heterandrium spp., which have short ovipositors and lay on external flowers, are infrequent and no effect on seed production has been documented. In the Colombian Andes, Idarnes spp. and Heterandrium spp. are the most frequent parasites of the Ficus andicola — Pegoscapus sp. mutualism, affecting 62 and 43 percent of syconia, respectively. Controlling for other factors that influence wasp and seed production, such as number of foundresses, syconium size and tree, we found that Idarnes reduced pollinator production by almost half but did not reduce seed production, whereas Heterandrium reduced seed production by 40 percent, and marginally affected pollinator production. Our results provide the first clear documentation of Heterandrium spp. impact on fig seed production. Whether the relative abundance of this genus is a generalized phenomenon in montane forest remains to be determined.     

Are Helicoverpa armigera and Tetranychus spp. populations still susceptible to pesticides? A Zimbabwean study

The African bollworm, Helicoverpa armigera (Hübner), and the cotton red spider mite, Tetranychus spp., are important pests of cotton in Zimbabwe. A study to assess H. armigera resistance to fenvalerate 20 EC (Cyano (3-phenoxyphenyl) methyl 4-chloro-α-(1-methylethyl)benzene acetate) and Tetranychus spp. resistance to amitraz 20 EC (n’-(2,4-dimethylphenyl)-n-[[(2,4-dimethylphenyl)imino]methyl]-n-) was conducted at the Cotton Research Institute (CRI) during the 2005/06 cotton-growing season. Field populations of H. armigera and Tetranychus spp. were collected from some of Zimbabwe’s major cotton-growing areas of Sanyati, Umguza, Chisumbanje, Chinhoyi and the CRI in Kadoma and exposed to bioassays. The African bollworm leaf disc technique and the red spider mite attached leaf-dipping technique were used to assess responses of the African bollworm and red spider mite to the pesticides. Susceptible laboratory populations served as the standard populations and their responses were compared with those of the field populations. The graphical method and MSTAT-C probit analysis computer program were used to calculate LC₅₀ values. Although the CRI field population, used as a reference population for the registration of H. armigera insecticides, had the highest LC₅₀ value (graphical?=?0.000100000; MSTAT-C?=?0.000088195) compared with all the other field populations, overall log-dose probit bioassays on all field-collected strains of the bollworm showed no resistance to the pyrethroid (RFs?=?0.04–0.54-fold). Tetranychus spp. showed very low levels of resistance (RFs?=?1.26–2.00-fold). Continuous monitoring of major cotton pests, especially H. armigera and Tetranychus spp., from all cotton districts of Zimbabwe is vital for early detection of resistance development.     

Actinomycotic intracavitary lung colonization

We describe four cases of actinomycotic intracavitary lung colonization and review the literature on the subject. Aspergillus fumigatus, A. niger, A. flavus, Pseudallescheria boydii are responsable for the majority of fungi intracavitary lung colonization (fungus ball). The similarities in clinical symptom (haemoptysis) and radiologic feature (pulmonary air meniscus) of fungus ball and actinomycotic intracavitary colonization prompted the investigation into a range of microorganisms, including Nocardia spp. [2–6] and Actinomyces spp. [1–5]. We report four cases of such actinomycotic syndrome, three of them in diabetic patients, and review briefly the literature.     

Spider assemblages associated with leaf litter of three tree species in central South Africa (Arachnida: Araneae)

Spiders were collected by sifting leaf litter of three common tree species, Cussonia paniculata sinuata, Olea europaea africana and Searsia lancea, in an undisturbed grassland habitat in central South Africa. The study aimed to collect baseline data on spider assemblage structure, seasonality and the effects of litter structure on spider assemblages. In total, 1385 spiders were collected, representing 26 families and 56 species. Four species, Obatala sp. (Amaurobiidae, 22.7%), Camillina maun Platnick & Murphy (Gnaphosidae, 17.0%), Proevippa sp. (Lycosidae, 11.4%) and Zelotes frenchi Tucker (Gnaphosidae, 9.2%) dominated the fauna. Spider abundance was the highest in Olea litter (n = 607), followed by Searsia (n = 453) and Cussonia (n = 325). Searsia had the greatest number of species (41 spp.), followed by Olea (35 spp.) and Cussonia (30 spp.). Both spider abundance and species richness per sample varied significantly between the tree species. Of the ten most abundant species, all but two showed a significant preference for particular litter types. Mean spider abundance and species richness per sample were the lowest in Cussonia litter, which was the deepest litter type, but with the most interstitial space, whereas mean abundance and species richness per sample were the highest in Olea litter, which was the shallowest and moderately compact in structure.     

Spider predation on a mirid pest in Japanese rice fields

Spiders are common generalist predators, and understanding their potential in biological control is important for the development of integrated pest management programs. In this study, predation by three groups of spiders on the mirid bug Stenotus rubrovittatus (Hemiptera: Miridae) in rice paddies was investigated using DNA-based gut-content analysis. A laboratory feeding study revealed that the detection half-lives of bug DNA in the spider gut at 25 °C was 3.4 days for Lycosidae and 1.5 days for Tetragnathidae. Individual spider predation on the mirid bug was investigated by detecting DNA of prey in field-collected spiders. In total, 1199 spiders were assayed from three spider groups: Pirata subpiraticus (Lycosidae), Tetragnatha spp. (Tetra-gnathidae), and Pachygnatha clercki (Tetra-gnathidae), which each differ in their preferred microhabitat as well as their predatory habits. Detection rates of prey DNA in spiders increased significantly with the density of prey across all spider groups. P. subpiraticus and Tetragnatha spp. predation showed a better fit to a saturated response curve to increasing prey density, while P. clercki showed a simple linear relationship with prey density. Densities of alternative prey species did not affect the detection rates of mirids. These results suggest that predation on pests by generalist predators in an agroecosystem is affected not only by prey abundance but also by predator preference for specific prey. Predator preference is therefore an important factor to consider when estimating the role of natural enemies as biological control agents.     

Environmentally induced post‐spin property changes in spider silks: influences of web type,spidroin composition and ecology

Many spiders use silk to construct webs that must function for days at a time, whereas many other species renew their webs daily. The mechanical properties of spider silk can change after spinning under environmental stress, which could influence web function. We hypothesize that spiders spinning longer‐lasting webs produce silks composed of proteins that are more resistant to environmental stresses. The major ampullate (MA) silks of orb web spiders are principally composed of a combination of two proteins (spidroins) called MaSp1 and MaSp2. We expected spider MA silks dominated by MaSp1 to have the greatest resistance to post‐spin property change because they have high concentrations of stable crystalline β‐sheets. Some orb web spiders that spin three‐dimensional orb webs, such as Cyrtophora, have MA silks that are predominantly composed of MaSp1. Hence, we expected that the construction of three‐dimensional orb webs might also coincide with MA silk resistance to post‐spin property change. Alternatively, the degree of post‐spin mechanical property changes in different spider silks may be explained by factors within the spider's ecosystem, such as exposure to solar radiation. We exposed the MA silks of ten spider species from five genera (Nephila, Cyclosa, Leucauge, Cyrtophora, and Argiope) to ecologically high temperatures and low humidity for 4 weeks, and compared the mechanical properties of these silks with unexposed silks. Using species pairs enabled us to assess the influence of web dimensionality and MaSp composition both with and without phylogenetic influences being accounted for. We found neither the MaSp composition nor the three‐dimensionality of the orb web to be associated with the degree of post‐spin mechanical property changes in MA silk. The MA silks in Leucauge spp. are dominated by MaSp2, which we found to have the least resistance to post‐spin property change. The MA silk in Argiope spp. is also dominated by MaSp2, but has high resistance to post‐spin property change. The ancestry of Argiope is unresolved, but it is largely a tropical genus inhabiting hot, open regions that present similar stressors to silk as those of our experiment. Ecological factors thus appear to influence the vulnerability of orb web spider MA silks to post‐spin property change. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 580–588.     

A Multi-Forest Comparison of Dietary Preferences and Seed Dispersal by <Emphasis Type="BoldItalic">Ateles</Emphasis> spp

Investigations of coevolutionary relationships between plants and the animals that disperse their seeds suggest that disperser-plant interactions are likely shaped by diffuse, rather than species-to-species, coevolution. We studied the role of dietary plasticity in shaping the potential for diffuse coevolution by comparing dietary fruit preferences and seed dispersal by 3 species of spider monkeys (Ateles spp.) in 4 moist forests in Colombia, Ecuador, Panama, and Surinam. In all forests, spider monkeys were highly frugivorous and preyed upon seeds of few species. We estimated dietary use of fruiting taxa based on absolute consumption and preference, which accounts for resource availability. Of the 59 genera that comprised the 20 most frequently consumed genera summed in each forest, only 3—Brosimum (Moraceae), Cecropia (Cecropiaceae) and Virola (Myristicaceae)—ranked within the top 20 at every forest. Most genera were within the 20 most frequently consumed at only 1 or 2 forests. Based on preferences, only 4 genera ranked in the 20 most-preferred in all 4 forests: Brosimum, Cecropia, Ficus (Moracae), and Virola. Patterns in fruit consumption and preference at the familial level were similar in that only 2 families—Myristicaceae and Moraceae—were in the 10 most-consumed or most-preferred in all 4 forests. Interforest variation in plant specific composition and abundances and supra-annual fruiting phenologies, combined with dietary flexibility of Ateles spp., may partly explain these patterns. Our results suggest that variation in plant community structure strongly influences dietary preferences, and hence, seed dispersal by spider monkeys. Thus, diffuse coevolution in spider monkey-plant relationships may be limited to few taxa at the generic and familial levels.     

Foraging at a safe distance: crab spider effects on pollinators

1. The ability of pollinating insects to discover and evade their predators can affect plant–pollinator mutualisms and have cascading ecosystem effects. Pollinators will avoid flowers with predators, but it is not clear how far away they will move to continue foraging. If these distances are relatively small, the impact of predators on the plant–pollinator mutualism may be lessened. The plant could continue to receive some pollination, and pollinators would reduce the time and energy needed to search for another patch. 2. A native crab spider, Xysticus elegans, was placed on one cluster in a small array of Baccharis pilularis inflorescence clusters, and the preferred short‐range foraging distances of naturally visiting pollinators was determined. 3. Nearly all pollinator taxa (honey bees, wasps, other Hymenoptera, and non‐bombyliid flies) spent less time foraging on the predator cluster. 4. The key result of this study is that inflorescences within 90 mm of the crab spider were avoided by visiting honey bees and wasps, which spent three‐ and 18‐fold more time, respectively, foraging on more distant flower clusters. 5. Whether honey bees can use olfaction to detect spiders was then tested, and this study provides the first demonstration that honey bees will avoid crab spider odour alone at a food source.     

Spider-fed bromeliads: seasonal and interspecific variation in plant performance

Background and Aims

Several animals that live on bromeliads can contribute to plant nutrition through nitrogen provisioning (digestive mutualism). The bromeliad-living spider Psecas chapoda (Salticidae) inhabits and breeds on Bromelia balansae in regions of South America, but in specific regions can also appear on Ananas comosus (pineapple) plantations and Aechmea distichantha.

Methods

Using isotopic and physiological methods in greenhouse experiments, the role of labelled (¹⁵N) spider faeces and Drosophila melanogaster flies in the nutrition and growth of each host plant was evaluated, as well as seasonal variation in the importance of this digestive mutualism.

Key Results

Spiders contributed 0·6 ± 0·2 % (mean ± s.e.; dry season) to 2·7 ± 1 % (wet season) to the total nitrogen in B. balansae, 2·4 ± 0·4 % (dry) to 4·1 ± 0·3 % (wet) in An. comosus and 3·8 ± 0·4 % (dry) to 5 ± 1 % (wet) in Ae. distichantha. In contrast, flies did not contribute to the nutrition of these bromeliads. Chlorophylls and carotenoid concentrations did not differ among treatments. Plants that received faeces had higher soluble protein concentrations and leaf growth (RGR) only during the wet season.

Conclusions

These results indicate that the mutualism between spiders and bromeliads is seasonally restricted, generating a conditional outcome. There was interspecific variation in nutrient uptake, probably related to each species'' performance and photosynthetic pathways. Whereas B. balansae seems to use nitrogen for growth, Ae. distichantha apparently stores nitrogen for stressful nutritional conditions. Bromeliads absorbed more nitrogen coming from spider faeces than from flies, reinforcing the beneficial role played by predators in these digestive mutualisms.     

Interspecific predation as a mortality factor among overwintering spiders

Summary Results from field experiments indicate that predation occurs among spruce-living spiders during winter in SW Sweden. Field observations of natural activity showed that Philodromus spp and Pityohyphantes phrygianus together make up 80% of the spiders active on spruce in winter. They are therefore potential predators on other overwintering spiders. Laboratory experiments were performed at +4° C to assess the importance of such predation between spiders. Small spiders (length <2.5 mm) had a mean winter mortality of 58% when kept together with large spiders (2.5 mm) which had a mean mortality of 3% only. Among the small spiders the Erigninae spp seemed to be more vulnerable to predation than other taxonomic groups. Predation also occurred when large P. phrygianus were kept together, but such predation caused mortality of less importance to the spider populations than the mortality among small spiders. Differences in spider density and food availability did not change this pattern. Considerable weight increase occurred in subadult P. phrygianus when fed during winter. This suggests that winter foraging specimens increase their fitness. Interspecific predation among spiders is suggested to be an important mortality factor in natural populations at high spider densities in November and December, when the ambient temperature often is above 0° C and when the density of large spiders is not yet substantially reduced by bird predation.     

The natural history of Myrmarachne melanotarsa,a social ant‐mimicking jumping spider

Abstract

Myrmarachne melanotarsa, an ant‐like jumping spider (Salticidae) from East Africa, is an accurate mimic of Crematogaster sp. and associates unusually closely with its models. M. melanotarsa is remarkable in that it forms dense aggregations and builds large nest complexes (numerous individually‐occupied nests connected to each other by silk). Other salticids (Pseudicius spp., Menemerus spp.) live with M. melanotarsa in the same nest complex. These aggregations, which can exceed 50 conspecific individuals per colony, are considerably larger than those few previously described, and seem to have primarily a protective function. We provide baseline information on the natural history of M. melanotarsa, paying particular attention to predatory behaviour and association with Crematogaster sp., and fit this within current theory on the function of sociality in spiders. Other unusual behaviour of M. melanotarsa includes “mouthing”, in which the spider opens and closes its chelicerae while pressing its mouthparts against nest silk. We investigated the role of prior presence of Crematogaster sp. on nest silk in eliciting this previously unreported behaviour.