Predator-prey interactions between web-invading jumping spiders and a web-building spider, Holocnemus pluchei (Araneae, Pholcidae)

Three species of web-invading salticid spiders, with different predatory strategies, were tested with Holocnemus pluchei in the laboratory: Portia fimbriata and Portia labiata , which practise aggressive mimicry, and Euyattus sp., which leaps from outside on to spiders in webs but does not practise aggressive mimicry. Portia was shown to be more efficient than Euryattus at catching H. pluchei. Portia fimbriata from Queensland was more consistent at using aggressive mimicry than was Portia labiata and was also more efficient at catching H. pluchei . The web-invaders that were more efficient at catching H. pluchei were also better able to avoid setting off bouncing, a special defence behaviour used by H. pluchei . An experiment, in which H. pluchei was artificially induced to bounce whenever the predator was near, provided additional evidence that bouncing is effective in defending H. pluchei against web-invaders.     

Spectral sensitivity in jumping spiders (Araneae,Salticidae)

1. We report here a psychophysical technique for studying the spectral sensitivity of jumping spiders (family Salticidae), based on a newly discovered oculomotor reflex. 2. Our results, obtained from Maevia inclemens (Salticidae), are compatible with electrophysiological findings of retinal cells maximally sensitive in the green and ultraviolet regions of the spectrum. 3. Sensitivity to longer wavelengths (greater than 650 nm) has been controversial. In our study jumping spiders are shown to have a broad spectral sensitivity function extending from the ultraviolet (330 nm) to the deep red (700 nm).     

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.     

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.     

Learning and discrimination of colored papers in jumping spiders (Araneae, Salticidae)

Color discrimination in jumping spiders Hasarius adansoni was examined by heat-avoidance learning in association with colored papers. The arena for the experiment was divided into two halves by a pair of colored papers. The colored papers used in this study were blue, green, yellow, red, white, gray and black. In training sessions, one half of the arena was heated from the bottom by a hot plate, and freely walking spiders were individually trained to avoid the heated half. In subsequent memory tests without heat, they consistently avoided the heat-associated colored papers. We found that jumping spiders could learn blue-green, blue-yellow, blue-red, blue-gray, green-yellow, green-red, green-gray, yellow-red, yellow-gray and red-gray patterns. Moreover, spiders trained with a blue-white pattern, a green-white pattern, a yellow-white pattern or a red-white pattern could discriminate the blue, green, yellow or red from black. It seems that jumping spiders can discriminate the blue, green, yellow and red papers by their hue, although brightness may also be used together with the color cue to discriminate colored papers.     

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.     

Predator-prey interactions between web-invading jumping spiders and Argiope appensa (Araneae, Araneidae), a tropical orb-weaving spider

A range of web-invading jumping spiders with different predatory strategies was tested with A. appensa in the laboratory: Mimetus maculosus (Mimetidae), Pholcus phalangioides (Pholcidae), Taieria erebus (Gnaphosidae), and 11 species of salticids. Spiders that are known to specialize at web-invading, either by leaping into webs or by walking slowly into webs and practising aggressive mimicry, captured A. appensa ; three salticid species not known to be web-invaders never did. Web-invaders that practised aggressive mimicry were more efficient than were species that only leapt into webs. Portia fimbriata from Queensland was the most consistent at using aggressive mimicry and was also the most efficient at catching A. appensa . Web-invaders that were more efficient at catching A. appensa were also better able to avoid setting off pumping, a special defence behaviour used by A. appensa . Portia fimbriata from Queensland was especially efficient at avoiding setting off pumping: P. fimbriata more consistently than other Portia made its final approach toward A. appensa by coming down from above the web on a dragline and making minimal contact with the web. An experiment, in which A. appensa was artificially induced to pump whenever the predator was near, provided additional evidence that pumping is effective in defending A. appensa against web-invaders.     

Distributional patterns of jumping spiders (Araneae: Salticidae) in Australia

Aim To analyse observed and predicted distributional patterns of selected salticid genera in Australia and to examine these distributions in the light of the origins and attributes of the fauna. To detect and compare the locations of regional hotspots when measured using different scales. Location Australia. Methods A total of 4104 locality records for specimens of 51 genera were stored in BioLink. Maps of observed and predicted (using bioclim ) distributions were prepared for each genus. The predicted distributions were combined to provide estimates of the number of genera likely to be found at each locality in the raster and for each of a set of landscape regions across Australia. The predictions were tested by comparing them with independent data sets. Results The Australian salticid fauna consists of radiations based on Oriental, Papuan and possibly Gondwanan forms, plus pantropical and peridomestic species. The predicted distributions of genera fall into a limited number of categories and these reflect the traditional biogeographical regions of Australia. Maximum regional diversity is predicted for central eastern Queensland, though diversity at single locations is highest further south in the New South Wales/Queensland border region. The locations of hotspots are therefore scale dependent. Patterns of distribution are not simply related to particular lifestyles. Fewer genera were predicted from inland Australia; however, recent work has shown that there are a large number of undescribed genera in the drier parts of Australia. The prediction maps allowed lists of genera potentially present in unstudied areas to be developed. Main conclusions (1) The current distribution of genera is predicted by their bioclimatic profiles rather than by their origins or ecology. Some Oriental genera, however, have not reached south‐western Western Australia, though bioclimatic conditions there are predicted to be suitable for them; (2) the highest diversity of genera is predicted to be in south‐eastern Queensland; (3) the results highlight the shortcomings of past fieldwork in Australia, which has concentrated on the areas with higher rainfall; (4) it seems likely that inland Australia will support a large, highly endemic, fauna adapted to the region, and ultimately perhaps 40 or more genera could be found in each region; (5) the results show the possibility of using the maps of predicted distribution of genera not only for biogeographical analyses but also for conservation management and survey purposes.     

Behavioural evidence of UV sensitivity in jumping spiders (Araneae: Salticidae)

Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-principal eyes. The existence of UV visual cells, however, does not prove that jumping spiders can see into the UV part of spectrum (300–400 nm) or whether such an ability plays any role in salticid intra-specific interactions. In the study reported herein, we performed behavioural experiments to test whether a UV−reflecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-specific communication. The absence of UV cues not only affected intra-specific behaviour by significantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspecific opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspecific mirror images by switching between agonistic and courtship displays. These findings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and sufficient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-specific communication in jumping spiders.     

Anti-predator crèches and aggregations of ant-mimicking jumping spiders (Araneae: Salticidae)

Myrmarachne assimilis , an ant-like jumping spider (Araneae, Salticidae) from the Philippines and a Batesian mimic of Oecophylla smaragdina , the Asian weaver ant, aggregates on leaves in the company of its model. All stages in this species' lifecycle are sometimes found in nest complexes (nests connected to each other by silk). Although aggregating and forming nest complexes is known for a few other salticid species, the aggregations of M. assimilis have some unusual characteristics. In particular, reproductive females appear to be most frequently found with other reproductive females in nest complexes, suggesting that nest complexes have a role in parental care and are often built by females joining other females. An egg-survival experiment showed that eggs in solitary nests were more often destroyed than were eggs in nest complexes, suggesting that, for females of M. assimilis , choosing aggregations as oviposition sites may be functionally akin to life insurance for their progeny.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 475–481.     

Consequences of sexual selection on feeding in male jumping spiders (Araneae: Salticidae)

The chelicerae of male Myrmarachne plataleoides , a salticid spider from Sri Lanka, are about five times the length of those of conspecific females. Intrasexual selection is thought to account for this structural dimorphism. The elongation of the male's chelicerae has resulted in morphological and behavioural differences in the feeding process of males and females. Males, unlike females, lack a fang duct and cannot envenom prey. During feeding, males use their fangs to skewer prey. The prey's contents are extracted from the holes in its cuticle where the spider's fangs protrude through the prey near the spider's mouth.     

The comparative study of the predatory behaviour of Myrmarachne, ant-like jumping spiders (Araneae: Salticidae)

The predatory behaviour of 31 species of Myrmarachne , ant-like salticids, was studied in the laboratory and the field. The ant-like morphology and locomotion of these spiders appears to function primarily in Batesian mimicry. No evidence was found of Myrmarachne feeding on ants. However, predatory sequences were found to differ considerably from those typical of salticids. Instead of stalking and leaping on prey, Myrmarachne lunged at prey from close range. Myrmarachne used its legs I to tap prey before lunging, another unusual behaviour for a salticid. Myrmarachne fed on a wide range of arthropod prey in nature and the laboratory, but appears to be especially efficient at catching moths. Also, Myrmarachne tends to open up, or enter into, other spiders' nests and eat other spiders' eggs. Myrmarachne males were less efficient than females, in laboratory tests, at catching various types of arthropod prey, but they appear to be as efficient as females at oophagy. Myrmarachne tend to use webs of other spiders as nest sites, but no evidence was found of Myrmarachne preying on spiders in webs. It appears that the unusual features of Myrmarachne's predatory and nesting behaviour are important in enabling these spiders to preserve their ant-like appearance.     

Prey-capture techniques and prey preferences of Corythalia canosa and Pystira orbiculata, ant-eating jumping spiders (Araneae, Salticidae)

Corythalia canosa from Florida is an unusual salticid because it is known to eat ants. This species' specialized behaviour for catching ants is described in detail for the first time and compared to its behaviour for catching other insects. Pystira orbiculata from Queensland is shown to be another ant-eating salticid, although its behaviour for catching ants seems less specialized than that of C. canosa. Three different types of tests of prey preference were carried out. In each type of test C. canosa and P. orbiculata took ants in preference to other insects. Another species of salticid, Trite planiceps from New Zealand, failed to eat ants in these tests, although T. planiceps often attacked then released the ants. Corythalia canosa's and P. orbiculata's preference for ants, and their prey-specific predatory behaviour for catching ants, are shown not to depend on prior experience with ants.     

Use of prey-specific predatory behaviour by North American jumping spiders (Araneae, Salticidae) of the genus Phidippus

Prey-capture behaviour of seven species of Phidippus is studied using two types of prey, house flies (adult Musca domestica ) and caterpillars (cabbage loopers, larval Trichoplusia ni ). Each species is shown to be a versatile predator which uses a different prey-specific prey-capture behaviour depending on whether prey is a fly or a caterpillar: spiders approached the two types of prey differently and leapt on them from different distances. Interspecific differences among Phidippus species are not pronounced, cxcept for variation in the distance from which spiders jumped and the spider's success at capturing a fly on the first try.     

Genital Morphology and Sperm Storage in Pholcus phalangioides(Fuesslin, 1775) (Pholcidae; Araneae)

The genital morphology of female Pholcus phalangioidesis examined to clarify the composition of the uterus externus and the place of sperm storage in this species. Two conspicuous pore plates serve as exits for glandular secretion that gets discharged into the uterus externus. The secretion accumulates close to the pore plates and to some extent in the region of the heavily sclerotized valve that separates the uterus externus from the uterus internus. During copulation, the male transfers spermatozoa and male secretions into the female genital tract where they are embedded and stored in the female secretion. As Ph. phalangioidesdoes not possess any separate sperm storage organs such as receptacula seminis, the glandular secretion serves to store and fix the sperm mass in a specific position within the uterus externus itself.     

A new mechanism of sound production by courting male jumping spiders (Araneae: Salticidae, Saitis michaelseni Simon)

Male Saitis michaelseni Simon (Araneae: Salticidae) produce sounds during courtship which can be heard several metres away. Courting males stridulate on dead leaves and are positioned on the opposite side of the leaf from the female. The courtship display contains both visual and acoustic elements. Courtship consists of three phases. In the first two phases, the male stridulates, and in the third phase, in which he makes tactile contact with the female, he alternates bursts of stridulatory sound with bouts of percussive sound in which the first pair of legs strikes the substratum. Stridulation apparently results from the thickened bases of short hairs on the anterior part of the abdomen moving over two files on the posterior part of the carapace. This stridulatory mechanism has not been previously reported for salticid spiders. The frequency spectra and amplitude modulation patterns of sounds produced by stridulation and percussion are presented.     

Web-building and predatory behaviour of Spartaeus spinimanus and Spartaeus thailandicus, primitive jumping spiders (Araneae, Salticidae) from South-east Asia

Behavioural data are provided for the first time for two species of Spartaeus, S. spinimanus from Singapore and Thailand and S. thailandicus from Thailand. These jumping spiders (Araneae, Salticidae), from the primitive subfamily Spartaeinae, build large sheet webs on tree trunks and they capture prey—especially moths—on or near the web by walking to and lunging at them. When walking, Spartaeus waves its palps and legs in an unusual way. In formal tests, Spartaeus captured moths more frequently than flies and captured both moths and flies more readily when with their webs than without their webs.