Mate-odour identification by both sexes of Evarcha culicivora, an East African jumping spider

Evarcha culicivora is an unusual salticid spider because each sex actively courts the other and both sexes make distinctive mate-choice decisions. Here we use olfactometer experiments for investigating the ability of each sex to identify potential mates on the basis of odour alone. Test spiders spent more time in the vicinity of opposite-sex conspecific source spiders, regardless of whether or not these source spiders had previously mated, when the alternatives were conspecific individuals of the same sex, juveniles or a control (no odour source). This trend held regardless of the test spider's and source spider's age after reaching maturity and, for male test spiders, it held regardless of the test spider's mating status. However, after females had mated they no longer expressed a preference for male odour.     

Cross‐Modality Effects of Prey Odour During the Intraspecific Interactions of a Mosquito‐Specialist Predator

One of the predictions from evolutionary game theory is that individuals will increase their willingness (i.e. become primed) to escalate aggression when they detect the presence of a limiting resource. Here, we test this prediction in the context of prey odour priming escalation decisions during vision‐based encounters by Evarcha culicivora. This East African jumping spider (Salticidae) feeds indirectly on vertebrate blood by actively choosing blood‐carrying female mosquitoes as preferred prey. Unlike many salticid species, it also expresses pronounced mutual mate choice. As predicted, we show here that, in the presence of odour from their preferred prey, both sexes of E. culicivora escalate during vision‐based same‐sex encounters. This is further evidence that the odour of blood‐carrying mosquitoes is salient to this salticid. For both sexes of E. culicivora, this particular prey may be a resource that matters in the context of intrasexual selection.     

Adaptive Timing as a Component of a Mosquito-Eating predator’s Specialization Profile

Evarcha culicivora, a salticid spider from East Africa, is a mosquito specialist which feeds indirectly on vertebrate blood by actively choosing blood-carrying mosquitoes as preferred prey and by actively choosing Anopheles as preferred mosquitoes. Here we investigate for the first time whether specialization by this predator is also expressed in the timing of its predatory activity. With data from field sampling and from systematically observing E. culicivora under semi-field conditions, we show that instances of predation tend to be most common in the early morning hours, this being when especially many night-feeding anthropophilic anopheline mosquitoes are resting while digesting blood acquired during the night. Experimental data show that E. culicivora is significantly more responsive to prey in the morning than in the afternoon, where ‘responsive’ includes being significantly more inclined to eat living prey, choose the preferred prey, approach a source of prey odor in the absence of visible prey and approach lures made from dead prey that can be seen but not touched or smelled. We found no significant diel pattern in E. culicivora’s inclination to mate and, although mate, plant and human odors are all known to be salient to E. culicivora, we found no significant diel pattern in response to any of these odors. Our findings suggest that E. culicivora’s innate pattern of predatory activity is adaptively adjusted in a way that facilitates predation on its preferred prey.     

Olfactory search-image use by a mosquito-eating predator

By choosing blood-carrying mosquitoes as prey, Evarcha culicivora, an East African salticid spider, specializes at feeding indirectly on vertebrate blood. It also has an exceptionally complex mate-choice system. An earlier study revealed that search-image use assists E. culicivora in finding prey and mates when restricted to using vision alone. Here we show that search-image use assists E. culicivora in finding prey and mates when restricted to using olfaction alone. After being primed with prey odour or mate odour (control: not primed with odour), spiders were transferred to an olfactometer designed to test ability to find a prey-odour or mate-odour source that was either ‘cryptic’ (i.e. accompanied by a masking odour source, Lantana camara) or ‘conspicuous’ (no L. camara odour). When tested with conspicuous odour, the identity of the priming odour had no significant effect on how many spiders found the odour source. However, when tested with cryptic odour, significantly more spiders found the odour source when primed with congruent odour and significantly fewer spiders found the odour source when primed with incongruent odour.     

The Trochidae and Turbinidae of the Kermadec Ridge (Mollusca: Gastropoda)

Abstract

Taieria erebus (Gnaphosidae) was found to be a versatile predator: it captured insects both cursorially (away from webs) and kleptopar-asitically (on alien webs); it captured spiders in both the presence and absence of webs; and it also ate the eggs of host spiders (oophagy). When T. erebus invaded webs, it was as an aggressive mimic — it performed a repertoire of vibratory behaviours to lure the host spider. Although T. erebus pursued and captured spiders on diverse web-types, it was more effective as a predator when invading densely (rather than sparsely) woven cribellate and non-sticky webs, and was especially effective on non-cribellate sticky webs. Gnaphosids are traditionally referred to as hunting spiders, but T. erebus built a small prey-capture web. T. erebus also preyed on segestriid spiders, then used their webs to catch more prey, this being an unusual example of a spider using, as a tool for predation, the spinning-work of another species from an unrelated family. T. erebus used specialised behaviours to prey on nesting cursorial spiders. Prey was either grasped or stabbed; the venom of T. erebus was highly potent against spiders. Experiments indicated that vision was of little or no importance in the predatory behaviour of T. erebus. The behaviour of T. erebus is compared to that of Portia, a web-building salticid spider which is very versatile in its predatory behaviour and has acute vision. T. erebus is discussed in relation to hypotheses concerning gnaphosid and salticid evolution.     

Complex display behaviour of Evarcha culicivora,an East African mosquito‐eating jumping spider

Abstract

Evarcha culicivora, an East African jumping spider (Salticidae), is an unusual predator because it feeds indirectly on vertebrate blood by choosing blood‐carrying mosquitoes as preferred prey. It also associates with particular plant species, Lantana camara and Ricinus communis. Here we document this species’ exceptionally complex display repertoire. In common with many other salticids, E. culicivora exhibits pronounced courtship versatility, with males using different tactics depending on the female's location and state of maturity. However, in contrast to most other salticids that have been studied, the males and the females of E. culicivora are both active at initiating and sustaining courtship, and both sexes are cannibalistic. Contrary to the emphasis in the literature on female spiders eating males, females of E. culicivora run a higher risk of being killed by males than vice versa during courtship. E. culicivora males also differ from other salticids that have been studied by adopting pronounced copulatory courtship. Male‐female interactions of E. culicivora are especially complex when encounters are in the foliage of L. camara and R. communis.     

Comparative biology of Portia africana,P. albimana,P. fimbriata,P. labiata,and P. shultzi,araneophagic, web-building jumping spiders (Araneae: Salticidae): Utilisation of webs,predatory versatility,and intraspecific interactions

Abstract

Portia is a behaviourally complex and aberrant salticid genus. The genus is of unusual importance because it is morphologically primitive. Five species were studied in nature (Australia, Kenya, Malaysia, Sri Lanka) and in the laboratory in an effort to clarify the origins of the salticids and of their unique, complex eyes. All the species of Portia studied were both web builders and cursorial. Portia was also an araneophagic web invader, and it was a highly effective predator on diverse types of alien webs. Portia was an aggressive mimic, using a complex repertoire of vibratory behaviour to deceive the host spiders on which it fed. The venom of Portia was unusually potent to other spiders; its easily autotomised legs may have helped Portia escape if attacked by its frequently dangerous prey. Portia was also kleptoparasitic and oophagic when occupying alien webs. P. fimbriata from Queensland, where cursorial salticids were superabundant, used a unique manner of stalking and capturing other salticids. The display repertoires used during intraspecific interactions were complex and varied between species. Both visual (typical of other salticids) and vibratory (typical of other web spiders) displays were used. Portia copulated both on and away from webs and frequently with the female hanging from a dragline. Males cohabited with subadult females on webs, mating after the female matured. Adult and subadult females sometimes used specialised predatory attacks against courting or mating males. Sperm induction in Portia was similar to that in other cursorial spiders. Portia mimicked detritus in shape and colour, and its slow, mechanical locomotion preserved concealment. Portia occasionally used a special defensive behaviour (wild leaping) if disturbed by a potential predator. Two types of webs were spun by all species (Type 1, small resting platforms; Type 2, large prey-capture webs). Two types of egg sacs were made, both of which were highly aberrant for a salticid. Responses of different species and both sexes of Portia were quantitatively compared for different types of prey. Many of the trends in behaviour within the genus, including quantitative differences in predatory behaviour, seemed to be related to differences in the effectiveness of the cryptic morphology of Portia in concealing the spider in its natural habitat (‘effective crypsis’). The results of the study supported, in general, Jackson & Blest’s (1982a) hypothesis of salticid evolution which, in part, proposes that salticid ancestors were web builders with poorly developed vision and that acute vision evolved in conjunction with the ancestral spiders becoming proficient as araneophagic invaders of diverse types of webs.     

The Attentive Spider: Search‐Image Use by a Mosquito‐Eating Predator

Evarcha culicivora, a jumping spider from East Africa, feeds indirectly on vertebrate blood by choosing blood‐carrying female mosquitoes as prey. It also has an unusually complex mate‐choice system. Here, we show that both sexes of E. culicivora can use mate‐finding search images and also use prey‐finding search images. In experiments, individuals were primed by seeing blood‐carrying mosquitoes, primed by seeing potential mates or not primed (control: saw neither). They were then introduced into an arena where the task was to find a blood‐carrying mosquito or a potential mate. In all instances, the prey or potential mates were dead individuals used as lures. The lure in the arena was either cryptic (i.e. hidden behind nylon netting and accompanied by distractors) or conspicuous (i.e. netting and distractors absent). When lures were conspicuous, the identity of the priming stimulus appeared to be irrelevant. However, when lures were cryptic, significantly more spiders found the lure that was congruent with the priming stimulus and significantly fewer spiders found the lure that was incongruent with the priming stimulus. On this basis, we conclude that the spiders were using search images for finding the lures and that search images were relevant only when the lure to be found was cryptic.     

Odour‐mediated response to plants by evarcha culicivora,a blood‐feeding jumping spider from East Africa

Abstract

Evarcha culicivora Wesolowska & Jackson, a salticid from the Lake Victoria region of East Africa, is known to associate with Lantana camara L. (family Verbenaceae) and Ricinus communis L. (family Euphorbiaceae), two plant species that are common in the same habitat. E. culicivora is an unusual salticid because, by choosing blood‐carrying mosquitoes as preferred prey, it feeds indirectly on vertebrate blood, and E. culicivora apparently also feeds on nectar taken from L. camara and R. communis. The experimental findings reported here show that the odour of these two plants is salient to E. culicivora. A Y‐shaped olfactometer was used in the experiments, with plant odour on one side and the other side a control (no odour). Juveniles, adult males and adult females chose the odour of L. camara and R. communis more often than the control.     

Male and Female Mate-Choice Decisions by Evarcha culicivora, An East African Jumping Spider

There has been a considerable recent interest in the criteria by which animals choose mates and in the extent to which mating systems tend to be based on mutual mate choice. In this study, we consider Evarcha culicivora, a salticid spider from East Africa. This species has some unusual characteristics, including active display by females as well as males, males that kill females more frequently than females kill males and wide intrasexual variation in body size. For females, larger males are especially dangerous. Here, we demonstrate, using two experimental designs (live‐mate choice and mount choice), that virgin males, virgin females and previously mated males prefer larger opposite‐sex individuals as potential mates, but mated females prefer smaller, safer males as potential mates.     

How cross-modality effects during intraspecific interactions of jumping spiders differ depending on whether a female-choice or mutual-choice mating system is adopted

An important prediction from game theory is that the value of a resource influences the level to which conflict escalates. Here we use jumping spiders (Salticidae) to consider this prediction in the context of species adopting different mating systems (‘female mate-choice’ and ‘mutual mate-choice’). Our experiments are designed for determining whether the odour of conspecific females, more than the odour of heterospecific females, primes males to escalate conflict with a potential same-sex rival and also whether the odour of conspecific males, more than the odour of heterospecific males, primes females to escalate conflict with a potential same-sex rival. Four species were studied: Evarcha culicivora, a species in which mutual mate-choice is pronounced, and Portia fimbriata, Portia africana, and Jacksonoides queenslandicus, more conventional salticids in which female mate-choice and male–male competition appear to be dominant. Our hypothesis is that, for all four species, there is strong competition between males for access to females and that, for E. culicivora, but not for the other three species, there is also strong competition between females for access to males. Our findings are consistent with this hypothesis, as we show that, although the odour of conspecific females primes escalation of vision-based male–male conflict for all four species, E. culicivora is the only species for which there is evidence of odour from conspecific males priming the escalation of female–female conflict.     

Long-duration whirling of Pholcus phalangioides (Araneae, Pholcidae) is specifically elicited by Salticid spiders

Long-duration whirling (gyrating of the body during several hours a day) was shown by the pholcid spider Pholcus phalangioides to salticid spiders and hardly ever to predatory spiders from eight other families in laboratory arenas. Long-duration whirling has not been reported so far, in contrast to short-duration whirling lasting less than a few minutes. Long-duration whirling may have the anti-predatory function of disturbing continual visual fixation of prey in attacking salticids, in contrast to short-duration whirling that has been demonstrated to favour survival of pholcids in the presence of all sorts of predatory spiders.     

Extreme ultraviolet sexual dimorphism in jumping spiders (Araneae: Salticidae)

Jumping spiders (Salticidae) have acute vision with some cells in the retina that are sensitive to ultraviolet (UV) spectra (< 400 nm). However, no study has documented the use of UV signals in salticids. To appreciate the function of UV vision, it is necessary to characterize the UV colours of salticids. In the present study, the UV and human-visible wavelengths of a tropical ornate salticid spider, Cosmophasis umbratica , were analysed using reflectance spectrometry to obtain evidence of sex-specific UV colours. An absolute sexual dimorphism in the UV colours of this salticid species was found. All of the body parts of adult males that are displayed to conspecifics during intra-specific interactions reflected UV (300–400 nm) light, whereas the adult females and juveniles did not reflect UV light from any body part. A great deal of variation was also found in the UV wavebands among males. This is the first full UV characterization of a salticid spider and the first study to demonstrate an extreme sexual UV dimorphism in jumping spiders. The findings obtained provide evidence that UV reflectance may comprise important sexual signals in jumping spiders.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 397–406.     

Salticid predation as one potential driving force of ant mimicry in jumping spiders

Many spiders possess myrmecomorphy, and species of the jumping spider genus Myrmarachne exhibit nearly perfect ant mimicry. Most salticids are diurnal predators with unusually high visual acuity that prey on various arthropods, including conspecifics. In this study, we tested whether predation pressure from large jumping spiders is one possible driving force of perfect ant mimicry in jumping spiders. The results showed that small non-ant-mimicking jumping spiders were readily treated as prey by large ones (no matter whether heterospecific or conspecific) and suffered high attack and mortality rates. The size difference between small and large jumping spiders significantly affected the outcomes of predatory interactions between them: the smaller the juvenile jumping spiders, the higher the predation risk from large ones. The attack and mortality rates of ant-mimicking jumping spiders were significantly lower than those of non-ant-mimicking jumping spiders, indicating that a resemblance to ants could provide protection against salticid predation. However, results of multivariate behavioural analyses showed that the responses of large jumping spiders to ants and ant-mimicking salticids differed significantly. Results of this study indicate that predation pressure from large jumping spiders might be one selection force driving the evolution of nearly perfect myrmecomorphy in spiders and other arthropods.     

The biology of ant-like jumping spiders: intraspecific interactions of Myrmarachne lupata (Araneae, Salticidae)

Myrmarachne lupata is an ant-like salticid in which males have very large chelicerae. The display repertoire of this species is unusually large and complex for a salticid spider. Each individual male uses one of three different mating tactics depending on the female's maturity and location. With adult females outside nests type 1 courtship occurs which seems to be a form of visual communication and includes specialized movements and postures of the legs, palps and body. With adult females inside nests, males use type 2 courtship, which seems to be a form of non-visual communication and consists primarily of probing with the legs on the silk; males mate with receptive females inside the nests. With subadult females, males first use type 2 courtship then spin an adjacent silken chamber and cohabit. After she moults and matures, mating occurs inside the nest. Vacant nests of conspecific females, but not those of another sympatric salticid species, elicit courtship behaviour from males. During male-male interactions, embracing occurs with the large chelicerae spread apart. Females and subadults also display, and different displays occur in interactions depending on the sex/age classes of the spiders involved. Despite the unusual morphology of these spiders, their individual displays are similar to those of more typical salticids. During copulation males stand beside the female instead of over or on her as occurs with typical salticids.     

The Nutritional Content of Prey Affects the Foraging of a Generalist Arthropod Predator

While foraging theory predicts that predatory responses should be determined by the energy content and size of prey, it is becoming increasingly clear that carnivores regulate their intake of specific nutrients. We tested the hypothesis that prey nutrient composition and predator nutritional history affects foraging intensity, consumption, and prey selection by the wolf spider, Pardosa milvina. By altering the rearing environment for fruit flies, Drosophila melanogaster, we produced high quality flies containing more nitrogen and protein and less lipid than low quality fruit flies. In one experiment, we quantified the proportion of flies taken and consumption across a range of densities of either high or low quality flies and, in a second experiment, we determined the prey capture and consumption of spiders that had been maintained on contrasting diets prior to testing. In both cases, the proportion of prey captured declined with increasing prey density, which characterizes the Type II functional response that is typical of wolf spiders. Spiders with similar nutritional histories killed similar numbers of each prey type but consumed more of the low quality prey. Spiders provided high quality prey in the weeks prior to testing killed more prey than those on the low quality diet but there was no effect of prior diet on consumption. In the third experiment, spiders were maintained on contrasting diets for three weeks and then allowed to select from a mixture of high and low quality prey. Interestingly, feeding history affected prey preferences: spiders that had been on a low quality diet showed no preference but those on the high quality diet selected high quality flies from the mixture. Our results suggest that, even when prey size and species identity are controlled, the nutritional experience of the predator as well as the specific content of the prey shapes predator-prey interactions.     

Field predation of twospotted spider mite in a New Zealand strawberry crop

Predation by naturally occurring predatory arthropods was investigated to explain variations in population numbers of twospotted spider mite (Tetranychus urticae Koch) between first and second season strawberry crops. Araneomorph spiders. European harvestman [Phalangium opilio (L.)], Tasmanian lacewing [Micromus tasmaniae (Walker)] and Pacific damsel bug [Nabis kinbergii Reuter] were the only predators found in high numbers. However, spiders and harvestment were more prevalent than lacewings and nabids. Laboratory feedings trials indicated spiders build horizontal webs in the plants and prey predominantly on small flying insects that shelter in the crops. Similar feeding trials cofirmed the palatability of TSSM to spiders and harvestmen. Immunological testing for proteins of TSSM, aphids, Collembola and leafrollers in the intestines of field collected European harvestman, spiders, Tasmanian lacewing and Pacific damsel bug confirmed European harvestman includes TSSM in its diet, but not in large enough quantities to exert a significant regulating pressure on TSSM populations. Lacewings and nabids include TSSM in their diets but only in very small quantities (2% and 1% respectively). Spiders do not take TSSM unless they drop or spin down onto the spider webbing. The immunological testing also showed European harvestman to be a polyphagous and opportunistic feeder. Prey residues were detected more frequently in harvestmen intestines at times of prey abundance which indicated a seasonality to harvestmen diet.      

Prey preferences ofPortia fimbriata,an araneophagic,web-building jumping spider (Araneae: Salticidae) from Queensland

Portia fimbriata from Queensland, a previously studied jumping spider (Salticidae), routinely includes web-building spiders and cursorial salticids in its diet, both of these types of prey being dangerous and unusual prey for a salticid. The present paper is the first detailed study ofP. fimbriata's prey preferences. Three basic types of tests of prey preference were used, providing evidence that (1)P. fimbriata males and females prefer spiders (both web-building spiders in webs and salticids away from webs) to insects; (2)P. fimbriata males and females prefer salticids to web-building spiders; (3)P. fimbriata males and females prefer larger spiders to smaller spiders; (4) there are intersexual differences in the preferences ofP. fimbriata for prey size, females preferring larger prey and males preferring smaller prey; and (5)P. fimbriata's prey preferences are not affected by a prior period without food of 2 weeks. When preferences were tested for by using both living, active prey and dead, motionless lures, the same preferences were expressed, indicating thatP. fimbriata can distinguish among different types of prey independent of the different movement patterns of different prey.     

Aggressive use of Batesian mimicry by an ant-like jumping spider

Batesian and aggressive mimicry are united by deceit: Batesian mimics deceive predators and aggressive mimics deceive prey. This distinction is blurred by Myrmarachne melanotarsa, an ant-like jumping spider (Salticidae). Besides often preying on salticids, ants are well defended against most salticids that might target them as potential prey. Earlier studies have shown that salticids identify ants by their distinctive appearance and avoid them. They also avoid ant-like salticids from the genus Myrmarachne. Myrmarachne melanotarsa is an unusual species from this genus because it typically preys on the eggs and juveniles of ant-averse salticid species. The hypothesis considered here is that, for M. melanotarsa, the distinction between Batesian and aggressive mimicry is blurred. We tested this by placing female Menemerus sp. and their associated hatchling within visual range of M. melanotarsa, its model, and various non-ant-like arthropods. Menemerus is an ant-averse salticid species. When seeing ants or ant mimics, Menemerus females abandoned their broods more frequently than when seeing non-ant-like arthropods or in control tests (no arthropods visible), as predicted by our hypothesis that resembling ants functions as a predatory ploy.     

Next-generation sequencing analysis of Pardosa pseudoannulata&#x27;s diet composition in different habitats

Spiders are the most common and predominant predators in terrestrial ecosystems. The predatory behavior of spiders affects the energy flow across the food web within an ecosystem. Traditiaonal methods for analyzing spider diets such as field observation, anatomy and faeces analysis are not suitable for spider experiments due to spiders’ special dietary behavior. The molecular method based on the specific primers of prey DNA seems to be inefficient either in spite of its wide application in diet analysis. As the next-generation sequencing (NGS) technology becomes prevalent in many different areas, several cases of the NGS-based analysis of mammal diets have been published. This study analyzed the diet differences of Pardosa pseudoannulata (Araneae: Lycosidae) in four habitats (a wetland, a tea plantation, an alpine meadow and a paddy field) by using the NGS technology, combined with the DNA barcode method. The results suggested that the Pardosa pseudoannulata feed on a broad range of prey, and 7 orders and 24 families of insects were detected in the four investigated habitats. Moreover, it is found that the diet diversity of Pardosa pseudoannulata is greatly influenced by their living environments and seasons. In a nutshell, this study established an NGS-based methodology for spider diets analysis, and the results provided some basic materials to inform the protection and utilization of the Pardosa pseudoannulata as a potential eco-friendly predator against pests.