Age and Sex-Based Differences in the Use of Prey Sensory Cues in Wolf Spiders (Araneae: Lycosidae)

Differences in foraging patterns mediated by sensory cues were examined between adult and juvenile male and female wolf spiders (Schizocosa rovneri; Lycosidae). Patch residence time for thirty-one spiders were tested among juveniles and adults in artificial foraging patches. Patches varied in sensory information provided by live prey (crickets) as follows: visual stimuli alone; vibratory stimuli alone; visual and vibratory stimuli together; and control (no stimuli). Spiders moved between patches for one hour, but could not feed. Adult Schizocosa rovneri use primarily visual information to determine patch residence time, but juveniles use vibratory cues as well. Significant age and sex-based differences in the use of sensory cues suggest that observed divergent foraging strategies are partly due to the use of different perceptual cues in prey detection.     

Species-Specificity of Chemical Signals: Silk Source Affects Discrimination in a Wolf Spider (Araneae: Lycosidae)

Female spiders deposit chemical cues that elicit male courtship behavior with silk. These cues are often assumed to be species-specific although male spiders may court in response to chemical cues of closely-related species. We used behavioral assays to test the extent of species discrimination of female chemical cues by male Schizocosa ocreata, a wolf spider (Lycosidae). Discrimination, expressed as relative courtship intensity of males, varied significantly with phylogenetic distance. Males did not discriminate between female cues of conspecifics and a sibling species, S. rovneri. Courtship response was intermediate for another species within the ocreata clade and not different from control for spiders outside the clade. These findings support the sibling species status of S. ocreata and S. rovneri, and also suggest the composition of female chemical signals is conserved across closely related wolf spider species.     

The Effect of Predator Chemical Cue Age on Antipredator Behavior in the Wolf Spider Pardosa milvina (Araneae: Lycosidae)

The wolf spider, Pardosa milvina, exhibits reduced movement when detecting chemical cues (silk and excreta) from a larger wolf spider, Hogna helluo. We tested if cue age influenced Pardosa activity. Pardosa response was measured during 1-h trials using video-tracking equipment. Five treatments of predator cues were used: 5-day-old, 1-day-old, 1-h-old, and fresh cues and a control lacking predator cues. Pardosa moved significantly more slowly on substrates with fresh or 1-h-old cues compared to all other treatments and spent less time walking in all Hogna treatments relative to the control except with 5-day-old cues. Pardosa survived longer in the presence of Hogna with fresh compared to older cues. Prey may evaluate cue age as a measure of predation risk and grade antipredator behavior accordingly.     

The Influence of Predator Sex on Chemically Mediated Antipredator Response in the Wolf Spider Pardosa milvina (Araneae: Lycosidae)

The wolf spider, Pardosa milvina, reduces activity in the presence of chemical cues (silk and excreta) from a larger predatory wolf spider, Hogna helluo. Hogna is sexually dimorphic in body size and males and females differ in their propensity to attack prey. Consequently, each sex may present different levels of risk to Pardosa. We measured predation risk of Pardosa in the presence of male or female Hogna. We also assessed Pardosa antipredator responses and survival in the presence or absence of previously deposited chemical cues from male or female Hogna. In the absence of predator chemical cues, Pardosa survived significantly longer in the presence of male Hogna compared with female Hogna. We then assessed Pardosa survival in the presence of chemical cues from each Hogna sex by placing Pardosa in containers previously occupied by a female Hogna, a male Hogna, or no Hogna (control). We then introduced a female Hogna into each container and measured predation latency. Pardosa survived significantly longer in the presence of female and male cues compared with the control treatment. Median survival time of Pardosa was over four times longer on substrates with female Hogna cues compared with male cues, but this difference was not statistically significant. We tested Pardosa activity levels in the presence of chemical cues from male or female Hogna. Both Hogna sexes were maintained in separate containers after which we placed an adult female Pardosa in one of the containers or a blank control container. Pardosa significantly decreased activity in the presence of chemical cues from either sex relative to the control. Activity was lowest on substrates with female Hogna cues, but not significantly lower than on substrates with male Hogna cues. Results suggest that chemical information from male or female Hogna significantly reduces Pardosa activity which results in increased survival.     

The Effect of Limb Loss on the Courtship and Mating Behavior of the Wolf Spider Pardosa milvina (Araneae: Lycosidae)

Limb loss is common in the wolf spider Pardosa milvina, appearing in nearly one third of adult males but occurring less frequently among adult females and juveniles. Since males wave their first pair of legs during courtship displays, the reproductive consequences of limb loss may be significant. We measured the courtship and mating effects of the loss of one, two, or four legs among adult male P. milvina. Missing one or two legs did not significantly reduce a male's ability to mate, but missing four legs was detrimental to mating success, reduced both courtship intensity and copulation duration, and increased cannibalism frequency. Results suggest behavioral flexibility in compensating for limited leg loss and a defensive function of the anteriormost legs to thwart female cannibalism attempts.     

The Effect of Predator Hunger on Chemically Mediated Antipredator Responses and Survival in the Wolf Spider Pardosa milvina (Araneae: Lycosidae)

The wolf spider Pardosa milvina exhibits effective antipredator behavior (reduced movement) in the presence of silk and excreta from a larger co‐occurring predatory wolf spider Hogna helluo. As the quantity and quality of the silk and excreta may vary with the hunger state of the predator, we tested if chemical cues from a hungry vs. satiated H. helluo affected the activity level and survival of P. milvina. Pardosa milvina response was measured on substrates containing chemical cues from (1) a satiated H. helluo, (2) a H. helluo that had been withheld food for 2 wk, (3) cues from adult domestic crickets (Acheta domesticus), or (4) a blank test substrate (20 replicates/treatment). Pardosa milvina activity level was recorded on each substrate over a 30‐min period using video‐tracking equipment (Videomex‐I^®; Columbus Instruments, Columbus, OH, USA). We then measured P. milvina survival in the presence of hungry or satiated H. helluo on cues from a hungry H. helluo, satiated H. helluo, or a blank control (2 × 3 design). Pardosa milvina significantly reduced activity in the presence of H. helluo cues and showed significantly less activity in the presence of cues from a hungry H. helluo compared with a satiated one. Cue type and predator hunger state significantly affected P. milvina survival in the presence of live predators. However, cues from hungry vs. satiated H. helluo resulted in no difference in P. milvina survival. Pardosa milvina can discriminate between hungry vs. satiated predators based on silk and excreta cues alone, but differences in behavior as a result of this discrimination did not translate into increased survival in the presence of a live predator.     

Silk production in adult females of the Wolf spider Pardosa amentata (Lycosidae, Araneae)

The production of silk in adult females of the wolf spider Pardosa amentata (CI.) has been studied. The role of female silk in courtship behavour is discussed on teh basis of experimental data.     

Assessing the conservation status of the strict endemic Desertas wolf spider,Hogna ingens (Araneae,Lycosidae)

The Desertas Islands (Madeira, Portugal) are the sole home of one of the largest and rarest wolf spider species, Hogna ingens (Blackwall 1857) (Araneae, Lycosidae). Despite its size, it inhabits a single valley in the North of the Deserta Grande Island, Vale da Castanheira, currently invaded by the herb Phalaris aquatica. This invasive species competes with the native flora and was subject to several eradication experiments, namely through fire and chemicals. The objectives of this work were to: (1) estimate the current distribution and abundance of H. ingens and respective trends; (2) evaluate the impact of the invasive plant and eradication methods on the spider population; (3) suggest future measures for the recovery of the species; and (4) evaluate its conservation status according to the IUCN criteria.The current distribution of H. ingens covers 23 ha, a recent reduction from its original 83 ha, corresponding to the entire Vale da Castanheira. A total of 4447 and 4086 adults and 71,832 and 24,635 juveniles were estimated to live in the valley during 2011 and 2012, respectively. We found a significant negative impact of P. aquatica cover on the presence and abundance of H. ingens and that chemical treatment specifically directed towards the invasive plant species may be the only way to effectively recover the spider's habitat. We suggest (1) regular monitoring; (2) extend chemical treatments; (3) ex-situ conservation with future reintroduction of adults. Based on the current area of occupancy (AOO) of H. ingens and its recent decline in both AOO and number of individuals, it was recently classified as Critically Endangered by IUCN and we suggest its urgent inclusion in the Habitats Directive species lists.     

Prey Capture Behaviour in the Social Spider Anelosimus eximius (Araneae: Theridiidae): Responses to Prey Size and Type

Some species of web building spiders use different capture tactics for different prey types. The main factors influencing the attack behaviour are the ability of the insect to escape, the risks of injury to the spiders and prey size. This study evaluated the effects of size and prey type on prey capture behaviour of the social spider Anelosimus eximius as influenced by the number of spiders attracted by prey movements that did not bite until the immobilization (bystanders) and the number of spiders that contributed to prey immobilization (catchers). We carried out a two‐factor (prey size and type) experiment offering prey belonging to four orders: Diptera, Lepidoptera, Hymenoptera and Orthoptera, in a size gradient within each prey type. Both factors influenced the number of spiders recruited as bystanders, but only prey body size influenced the number of catchers in the subduing process. The possible advantages of the presence of bystanders around the interception site are discussed.     

Effects of Early Contact with Maternal Parent on Locomotor Activity and Exploratory Behavior in Spiderlings of Hogna carolinensis (Araneae: Lycosidae)

In this study we investigated the effect of rearing conditions (stimulus complexity) on the locomotor activity and exploratory behavior of spiderlings of Hogna carolinensis in a novel open field arena. Experimental groups consisted of spiderlings that were allowed to remain with their maternal parent for 1 day (group 1), 3 days (group 2), and 5 days (group 3) after emergence from their egg sacs, and those who had no contact (group 4) with a maternal parent. Spiderlings that had physical contact with their mothers for 3 and 5 days required significantly less time to enter the arena, to reach the central grid area of the arena, and for an initial return to the start box than spiderlings in groups 1 and 4. In addition, spiderlings in groups 2 and 3 exhibited a significantly greater number of grid crossings as compared to groups 1 and 4, and spent more time in the arena. This is the first demonstration that environmental complexity, in the form of a social factor such as physical contact with a maternal parent, can affect the subsequent behavior of spiderlings.     

Study on Chemosensitive Hairs in Wolf Spiders (Araneae, Lycosidae) by Scanning Electron Microscopy

The occurrence of chemosensitive hairs in some lycosid species is examined. The distribution and shape of such hairs dorsally on the male subadult palpal tarsus and the cymbium are compared. In certain species (e.g. of the genera. Pardosa and Alopecosa) the cymbium has a dense covering of these hairs while there are rather few of these in the male subadult palpal tarsus. The cymbium of Aulonia atbimana has comparatively few chemosensitive hairs dorsally, a condition supposedly related to the web-building habit in this species. Indications are given that the cymbial chemosensitive hairs are involved in the detection of presumed contact sex pheromones produced by the female. Certain intergeneric differences in the shape of the apical part of the cymbial chemosensitive hairs are noted.     

Transgenic Cabbage Expressing Cry1Ac1 Does Not Affect the Survival and Growth of the Wolf Spider,Pardosa astrigera L. Koch (Araneae: Lycosidae)

Both herbivores that consume transgenic crops and their predators can be exposed to insecticidal proteins expressed in those crops. We conducted a tritrophic bioassay to evaluate the ecotoxicological impacts that Bt cabbage (Brassica oleracea var. capitata) expressing Cry1Ac1 protein might have on the wolf spider (Pardosa astrigera), a non-target generalist predator. Enzyme-Linked Immunosorbent Assays indicated that protein levels were 4.61 ng g^-1 dry weight in fruit flies (Drosophila melanogaster) fed with the transgenic cabbage and 1.86 ng g^-1 dry weight in the wolf spiders that preyed upon them. We also compared the life history traits of spiders collected from Bt versus non-Bt cabbage and found no significant differences in their growth, survival, and developmental rates. Because Bt cabbage did not affect the growth of fruit flies, we conclude that any indirect effects that this crop had on the wolf spider were probably not mediated by prey quality. Therefore, exposure to Cry1Ac1 protein when feeding upon prey containing that substance from transgenic cabbage has only a negligible influence on those non-target predatory spiders.     

A revision of the genus Trabaea Simon (Araneae: Lycosidae)

The genus Trabaea Simon is revised. Nine species are included in the genus of which two are described as new. Trabaeosa straeleni Roewer is newly synonymised with Trabaea purcelli Roewer. A key to the species of Trabaea is provided and the relationships of the genus are discussed.     

Trophic exchange in Pardosa hortensis (Lycosidae, Araneae)

Young Pardosa hortensis not only need their mother's help to leave their cocoon once developed (about 20 days), as they are unable to open it by themselves, but also during the period they are carried around in the cocoon. Using radioactive markers, indirect evidence revealed that the mother periodically opens the cocoon to feed her young and reseals it with fresh silk. Water is probably the main component in trophic exchange.     

Burrow-blocking behaviour in Geolycosa wrightii (Araneae: Lycosidae)

Patterns of behaviour associated with preventing wind-blown sand from entering the burrows of the wolf spider Geolycosa wrightii were investigated in a laboratory study. The method of closing the burrow depended upon the rate of sand entry. The spider employed a web block at low rates and used its body to block at high rates.     

我国四种舞蛛记述

本文记述我国舞蛛属Alopecosa1新种：林站舞蛛A．1inzhan sp．nov．,及3新纪录种：方隔舞蛛A．akkolka Marusik,1994、客居舞蛛A．inquilina(Clerck,1757)和独行舞蛛A．solivaga(Kulczynski,1901)。新种近似于A．sokhondoensis Logunov et Marusik,1994,但新种外雌器中隔扩展部端部向前方延伸较明显,超出中隔柄部,交配管较细长,而后者外雌器中隔扩展部向前方延伸不明显,未超出中隔柄部,交配管较短;另外2者在前眼列各眼相对大小和间距方面也有差别。     

Prey preferences of six species of Carabidae (Coleoptera) and one Lycosidae (Araneae) commonly found in UK arable crop fields

Abstract: Laboratory experiments were used to determine the feeding preferences of six carabid beetles and one lycosid spider on aphid and collembolan prey. The first investigation used only five species of carabid Pterostichus melanarius Illiger, Pterostichus madidus F., Harpalus rufipes DeGeer, Nebria brevicollis F. and Carabus violaceus L., which had been caught most commonly in pitfall traps in the headland region of arable crop fields. When offered Brevicoryne brassicae L., Sitobion avenae F., Metopolophium dirhodum Walker and Rhopalosiphum padi L. as prey items, the species consistently consumed in high numbers was M. dirhodum . In subsequent experiments four carabids Pterostichus cupreus L., P. melanarius, P. madidus. H. rufipes and a lycosid spider Trochosa ruricola DeGeer whose distribution was shown by pitfall trapping to extend throughout the arable crop, were the chosen predators. These predators were offered a choice between M. dirhodum and entomobryid collembolans (a recognised alternative prey item) to gauge their preference between the two prey types. Both male and female P. cupreus and P. melanarius showed a significant preference for the aphid prey, while there was no significant preference displayed by the other species. The effect of temperature on the voracity of these five predators fed on M. dirhodum was investigated. There were significant differences in the number of aphids consumed by the species and sexes at the different temperatures. Regression analysis on the mean numbers of aphids eaten by each sex of the five predators, showed that in the majority of cases there was a significant increase in predation with increasing temperature. In considering the dietary preferences illustrated by these experiments, it appeared that P. cupreus and P. melanarius offered the greatest potential in controlling aphids on arable crops.     

Circadian Structural Changes in the Retina of Lycosa tarentula (Araneae: Lycosidae)

Daily structural changes of the rhabdoms are described in the four eye types of a lycosid spider submitted to laboratory conditions: LD 12:12 (light on at 08.00, 100 lux). From a study of animals submitted to constant darkness during fourteen days, rhabdom turnover was shown to be circadian. Each type of retina exhibits its own rhythmic turnover of rhabdoms. Anterior-lateral, posterior-median and lateral eyes are mostly diurnal; anterior-median retinae comprise 300 receptors with mainly nocturnal functioning and 150 receptors with mainly diurnal functioning. A correlation was found between rhythms of locomotor activity, other activity, and rhabdom turnover in L. tarentula suggesting that the same pacemaker controls these different rhythms.     

Circadian Structural Changes in the Retina of Lycosa tarentula (Araneae: Lycosidae)

Daily structural changes of the rhabdoms are described in the four eye types of a lycosid spider submitted to laboratory conditions: LD 12:12 (light on at 08.00, 100 lux). From a study of animals submitted to constant darkness during fourteen days, rhabdom turnover was shown to be circadian. Each type of retina exhibits its own rhythmic turnover of rhabdoms. Anterior-lateral, posterior-median and lateral eyes are mostly diurnal; anterior-median retinae comprise 300 receptors with mainly nocturnal functioning and 150 receptors with mainly diurnal functioning. A correlation was found between rhythms of locomotor activity, other activity, and rhabdom turnover in L. tarentula suggesting that the same pacemaker controls these different rhythms.     

The fine structure of the visual system of Lycosa (Araneae: Lycosidae)

Summary Wolf spiders have four pairs of eyes distributed in three rows. The first row which lie in the frontal region of the caparace, just above the chelicera, contains four eyes: a medial pair known as the anterior medial eyes (AM eyes or principal eyes) and two smaller eyes known as the anterior lateral eyes (AL eyes). The second row which is located also in the frontal region of the prosoma consists of two big eyes. These are the posterior median eyes (PM eyes). The third row contains the posterior lateral eyes (PL eyes) which lie in the flanks of the prosomal caparace. The AL, PM and PL eyes are the so-called secondary eyes.The electron microscope shows that the AM eye photoreceptor cells have the rhabdomere in their distal segment, just behind the vitreous body. The rhabdomere consists of closely packed microvilli about 0.5 long exhibiting a uniform diameter of 500 Å. Each rhabdom consists of two rhabdomeres. The distal segment of the photoreceptor has a prismatic shape with four or five faces depending of their location within the retina.The distribution of the rhabdoms follows two different patterns or organization. In the peripheral portion of the retina they lie oriented either parallel or perpendicular to the retinal radii. In this zone most cells have four sides while in the central region five sided cells are predominant. These cells bear microvilli in three of their five faces and the rhabdoms show no preferential mode of orientation. Each retina contains approximately 450 photoreceptors. In the secondary eyes the rhabdoms lie far from the vitreous body behind the level of the cell nuclei. A light reflecting layer or tapetum is present in the three pairs of secondary eyes. The microvilli forming the rhabdomeres of the AL eyes are 0.5 long and 500 Å wide, while the microvilli of the rhabdomeres in the PM and PL eyes are longer and thicker (1.5 long and 550–660 Å wide). In these eyes the rhabdomeres are surrounded by abundant extracellular material. Like in the principal eyes each rhabdom consists of two rhabdomeres.In the AL eyes the photoreceptor cells send out collateral branches which end, without any specialization, in contact with other photoreceptors. Clear fibers running parallely to the tapetum have been found in the secondary eyes. These fibers show specialized regions corresponding to the zones of contact with the photoreceptor cells. These areas are characterized by an increased density of the membranes and groups of vesicles (the vesicles lie within the fibers).The optic nerves consist of photoreceptor axons, glial cells and a fibrous perineural sheath. The AM and AL eyes are connected to the CNS by a single compact optic nerve while in the PM and PL eyes the optic nerve consists of several individual bundles. The total number of optic fibers entering into the brain is about 12.000.A layer of glial cytoplasm covers each photoreceptor axon and the mesaxons appear as double lines which bifurcate frequently.Research sponsored by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR Grant Nr. 618-64.