Drop and swing dispersal behavior of a tropical wandering spider: experiments and numerical model

Summary When exposed to certain air flows spiderlings of the wandering spider Cupiennius getazi (Ctenidae) drop from their dwelling plant and swing in the wind from a gradually lengthening dragline. If body contact is made with a nearby substrate the spiderling detaches. We refer to this form of aerial dispersal as the drop and swing dispersal behavior (DASDB). The dragline being only up to about 70 cm long and only rarely ruptured by the drag forces of the wind, this is a close range type of dispersal as opposed to the ballooning known for many other species of spiders. DASDB is readily elicited in spiderlings at an age of ca. 9 days (outside egg sac). At this age their mass is 1.26 ±0.35 mg and their yolk usually depleted. They then start to catch prey and escape from the unfavorable conditions in the small space around the egg sac where hundreds of spiderlings compete. Air flow rates effectively eliciting DASDB in the laboratory are between 0.2 m/s and 1.5 m/s. The number of spiderlings showing DASDB increases considerably if the air flow is turbulent as opposed to laminar. A numerical model defining the window within which DASDB is supported mechanically was developed from theoretical considerations. Taking the effective wind speeds and the mechanical properties of the dragline, the model accounts very well for the fact that actual rupture of the dragline was observed only rarely in C. Getazi. Other features of the DASDB are also correctly predicted. The model is not only applicable to DASDB but also to the drop and swing preballooning behavior known to occur in several other species of spiders.Abbreviations DASDB drop and swing dispersal behavior     

Adaptive advantages of maternal care and matriphagy in a foliage spider,Chiracanthium japonicum (Araneae: Coubionidae)

I examined the function of maternal care in a foliage spider,Chiracanthium japonicum. Females of this species make breeding nests with rolled-up grass leaves and provide themselves to spiderlings as food at the end of maternal care. By removing mothers from their offspring at 2 different times, the effects of maternal care on egg and spiderling survival rates were estimated separately. Mother attendance greatly improved survival and development of eggs as well as spiderlings. Detailed observations on the fate of immatures in breeding nests with and without their mothers showed lower hatching and spiderling emergence rates when mothers were removed. Furthermore, spiderlings that fed on their mother’s body showed accelerated growth and quickly molted into the 3rd instar with the delay of dispersal. This suggests that matriphagy, or eating the mother, enables spiderlings of this species to disperse at a later instar. Therefore, I conclude that the maternal care of this spider consists of guarding offspring, supporting offspring development and feeding spiderlings.     

Ontogenetic Changes in Web Design in Two Orb‐Web Spiders

The first orb web built by newly hatched spiders resembles the adult web in its overall form and structure. However, many details show ontogenetic changes. One possible explanation for these changes is that the tiny early‐instar spiders with their minute brains will make more mistakes and build less ‘perfect’ orb webs than older and larger juveniles and adults. To test this hypothesis, known as the size limitation hypothesis, I analysed orb webs from three developmental stages, spiderlings, juveniles and adult females, in two neotropical orb‐web spiders, the araneid Eustala illicita and the nephilid Nephila clavipes. Neither species showed clear signs of being behaviourally limited or more prone to committing errors as spiderlings than were older juveniles or adults. These findings therefore do not support the size limitation hypothesis in either species. Finally, I looked for evidence of the ‘biogenetic law’, which predicts that juveniles should build less derived orb webs than the adults. Evidence for this was found in E. illicita, but not in N. clavipes.     

Contrasting patch choice behaviour by immature ambush predators, a spider (Misumena vatia) and an insect (Phymata americana)

1. Spiderlings of the crab spider Misumena vatia and nymphs of the ambush bug Phymata americana normally ambush prey in flowers, as do the adults. The immatures of M. vatia are more mobile, by ballooning, than the ambulatory but largely sedentary adult female spiders, but the apterous immatures of P. americana are less mobile than the alate adults. The aim of the work reported here was to investigate how immatures, as compared with adults, select sites from which to ambush their prey. 2. Individual immatures of both species were released in experimental arenas with variously manipulated natural stems: normal, with and without leaves, and with and without flowers of three species of plants. 3. The spiderlings and nymphs showed discriminatory behaviour but not in accordance with optimal foraging in either case. The spiderlings chose more leafy stems than any other kind of stem. For the nymphs, the importance of leaves was less marked, food apparently being more important than shelter. 4. Neither of the predators discriminated among flowering stems of Solidago canadensis, Daucus carota, and Cirsium arvense. 5. In other experiments, in which flowered and deflowered stems were located in two separated groups in the arena and the individual was released in a bare area between the two groups, the spiderlings chose either group as predicted by chance but the nymphs showed a slight preference for the flowered sector. Nevertheless, once in either of the groups, the predators showed similar behaviour in choosing leafy stems more often than other stems. 6. Nymphs of P. americana are much more selective than adults but spiderlings of M. vatia are less selective than adult females. These results appear to accord with the time and energy costs of changing hunting sites, walking being slower than flying or ballooning. 7. The results indicate the need to include other parameters, such as enemy‐free space and time spent in not being able to forage, in the analysis of foraging behaviour.     

Offspring recognition by mother crab spiders with extreme maternal care

Maternal care is provided by several spider species, but there are no reports of mother spiders recognizing their young, which suggests that maternal care can be exploited by unrelated individuals. Diaea ergandros, a crab spider with extreme, sacrificial maternal care, does accept unrelated spiderlings (ca. 43.9% of spiderlings) into its nest in areas of high nest density. However, a field and a laboratory experiment with mother spiders and natural and adoptive spiderlings demonstrated that mothers did recognize their own offspring. Recognition was not expressed in survival as adopted (unrelated) spiderlings had similar survival rate to that of natural offspring. Instead it was displayed in growth; mother D. ergandros caught large prey items for their own offspring, but not for adopted spiderlings, and so natural offspring grew more than adopted spiderlings. Also, mothers produced trophic oocytes, which are important for the sacrificial care that influences spiderling survival, only when they lived with their own offspring.     

Juvenile bolas spiders attract psychodid flies

Large immature and mature female bolas spiders of the genus Mastophora attract certain male moths by aggressive chemical mimicry of those moth species' sex pheromones. These older spiders capture moths by swinging a bolas (i.e., a sticky globule suspended on a thread) at the approaching male moths. Juvenile bolas spiders do not use a bolas, but instead use their first two pairs of legs to grab prey, which our field observations suggested were primarily nematocerous Diptera. Our field experiments over a 2-year period demonstrated that juvenile bolas spiders attract moth flies (Psychodidae), with each species apparently specializing on a particular prey species. In three experiments, sticky traps containing young Mastophora phrynosoma spiderlings consistently captured significantly more male Psychoda phalaenoides than were captured on traps containing spiderlings of other Mastophora species or no spiderlings (control traps). Results from two of the three experiments suggested that Mastophora hutchinsoni spiderlings attract male Psychoda trinodulosa. Only two of our experiments included Mastophora bisaccata and those produced contrasting results. In the first experiment, M. bisaccata appeared to attract P. phalaenoides, albeit in lower numbers than were captured on traps containing M. phrynosoma. However, in a second experiment the following year, M. bisaccata spiderlings attracted Psychoda satchelli, a species that had not been caught on any traps the previous year. As suggested by a systematist four decades ago, the taxon currently called M. bisaccata may consist of two or more sibling species, which could account for the contrasting results obtained from our two experiments involving M. bisaccata. This is the first reported evidence that, during early developmental stadia before these spiders attract moths, juvenile bolas spiders attract their prey.     

Antioxidant responses of the pest natural enemy Hylyphantes graminicola (Araneae: Linyphiidae) exposed to short-term heat stress

Temperature is a critical abiotic factor that causes physiological changes in arthropods. However, little is known about the effect of heat stress on the antioxidant responses of Araneae species. Hylyphantes graminicola is a dominant predator in many cropping systems in China. In the present study, the effect of short-term heat stress (36, 38, 40 or 42 °C) on the reactive oxygen species (ROS) levels, the activities of antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], peroxidases [POD] and glutathione-S-transferases GST]), total antioxidant capacity (TAC), malondialdehyde (MDA) concentrations and survival of H. graminicola spiderlings and adults were investigated. The results showed that H. graminicola adults had a significantly higher survival rate compared to spiderlings at 40 °C. The heat stress increased ROS contents in H. graminicola. The SOD, CAT, POD and GST activities increased in spiderlings and adults under heat stress. These data suggest a defensive function for these enzymes in alleviating oxidative damage. Specifically, SOD plays a key role in reducing the high level of superoxide radicals in spiderlings and adults. Moreover, the POD and CAT capabilities for scavenging H₂O₂ in spiderlings were similar, and CAT may play a more important role than POD in scavenging H₂O₂ in adults at 42 °C. The spiderling TAC increased significantly at 40 and 42 °C, and the adult TAC was stable at 36–40 °C but decreased at 42 °C. These data suggest that TAC was insufficient in H. graminicola adults under more severe stress conditions. These results further our understanding of the physiological response of Araneae species exposed to heat stress.     

Side-effects of insecticides on two erigonid spider species

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

Seasonal changes in resource allocation within an individual offspring of the wolf spider, Pardosa pseudoannulata (Araneae: Lycosidae)

Abstract.  Seasonal changes in resource investment into individual offspring are well documented, but no attention has been paid to the allocation of the invested resource among the body parts of the offspring. In the present study, seasonal changes in the absolute and relative sizes in a spiderling of the wolf spider Pardosa pseudoannulata Boes. et Str. are investigated, and the relationship between spiderling body size and the ability to moult during a food shortage is clarified. Spiderlings that emerge in November have a significantly larger cephalothorax and abdomen than those that emerge in June. In addition, the abdomen–cephalothorax size ratio is significantly greater in November than in June offspring. Under limited food availability conditions, only 40% of spiderlings moult. Nymphs that do moult have a significantly larger cephalothorax, abdomen and abdomen–cephalothorax size ratio than nymphs that do not moult. Thus, both the quantity of resources invested in the cephalothorax and abdomen of a spiderling and the proportional allocation of resources between the two body parts change seasonally in Pa. pseudoannulata ; alteration of the resource allocation occurs in late autumn. Larger spiderlings of Pa. pseudoannulata that emerge in late autumn would be able to develop into advanced instars even during food shortage, and therefore may have better overwintering survival rates.     

Spiderling sex ratio and maternal investment in the bolas spider Mastophora cornigera (Araneae,Araneidae)

Male Mastophora cornigera exit egg sacs as adults, which allowed us to determine spiderling sex ratios and patterns of maternal investment in this species. We collected 15 egg sacs produced by seven mothers, which yielded 1945 emergent spiderlings which were sexed, 1850 of which were weighed. Two emergent broods were significantly male and female biased and were unaffected by pre-emergence mortality. The weights of male and female spiderlings differed in eight broods, with males and females being heavier in four cases each. Five of these broods were derived from multiple egg sac sets produced by one mother, and in each case, the total mean male and female spiderling weights for all broods in a set were biased in the same direction as the biased brood(s) within that set. Mean emergent spiderling weight was independent of brood size and sex ratio for both males and females. Despite such independence, sex allocation in M. cornigera can favor sons, daughters, or both equally, and by numbers, by weight, or both at once. The proximate mechanisms and adaptive significance of such variability is unknown. We also review evidence for gender-biased allocations in arachnid offspring and suggested mechanisms for their applicability to M. cornigera.     

The role of spider cocoons in controlling desiccation

Summary The abilities of the cocoons of the spiders Mecynogea lemniscata and Argiope aurantia to protect the enclosed egg and spiderling stages from desiccation were investigated in the laboratory under controlled humidities, and in the field under ambient conditions. For M. lemniscata, which has a relatively small clutch (8–30 eggs) and remains in the cocoon for approximately 9–10 months, removal of the cocoon had no effect on water loss from the egg stage, nor did it adversely affect hatching or molting success. Cocoon removal did, however, significantly affect water loss and, consequently, survival in the spiderling stage at all humidities in the laboratory and in the field. The importance of the cocoon for survival is probably related to the unusually long time M. lemniscata spiderlings spend in the cocoon overwintering. For A. aurantia, which has a substantially larger clutch size (300–1400 eggs) and remains in the cocoon for a shorter 6–7 months, cocoon removal had no effect on water loss, egg hatching success, molting success, nor spiderling survival. The lack of an effect suggests that other factors (e.g., relative humidity at the oviposition site, or a large clutch size) may be more important in controlling water loss for A. aurantia.     

Preference for feeding on honey solution and its effect on survival,development, and fecundity of Ebrechtella tricuspidata

Members of the spider families Thomisidae, Salticidae, Miturgidae, Anyphaenidae, and Corinnidae have been observed on floral and extrafloral nectaries of plants, where they are presumably feeding on nectar. Nectar feeding is a phenomenon that has long intrigued biologists. However, few studies have focused on the effect of nectar on biological characteristics of these spiders. The aim of this study was to determine whether crab spiders, Ebrechtella tricuspidata (Fabricius) (Araneae: Thomisidae), show an active preference for honey solution (a simulated nectar source) and to test the effect of honey solution on the survival and development time of spiderlings and the fecundity of adult E. tricuspidata. The results showed that the number of females feeding on the 10, 20, and 30% honey solution was significantly higher than those feeding on water alone, and there was no difference in the number of females feeding on the three concentrations of honey solution. Significantly more E. tricuspidata preferred feeding on the 20% honey solution, and they spent significantly more time feeding on 20% honey solution than on water, regardless of whether they were males or females, adults or spiderlings. Ingestion of honey solution significantly increased the survival and shortened the development time of E. tricuspidata. Female spiders that fed on honey solution had a shorter pre‐oviposition period and laid more eggs than those given only water. Our results suggest that nectar could be a high‐quality supplementary food to maintain normal growth and metabolism in spiderlings and adult female spiders in nature.     

Adult male bolas spiders retain juvenile hunting tactics

Bolas spiders in the genus Mastophora exhibit extreme sexual size dimorphism. In temperate regions, the diminutive males become adults about 2 months before females mature. Late-instar and adult females attract certain male moths by aggressive chemical mimicry of those moth species' sex pheromones. While hunting, these larger female spiders hang from a horizontal silken line and capture moths by swinging a “bolas” (i.e., a sticky globule suspended on a thread) at the approaching moths. Small, early-instar bolas spiders of both sexes attract moth flies in the genus Psychoda, which they capture without using a bolas or web. Instead, they position themselves along leaf margins and use their front two pairs of legs to grab approaching prey. The predatory habits of adult male bolas spiders have never been reported. Our field experiments demonstrated that adult males of the bolas spider Mastophora phrynosoma attract adult male Psychoda phalaenoides. Each year during our 3-year study, significantly more P. phalaenoides were captured on sticky traps baited with live adult male M. phrynosoma than on unbaited control traps. Thus, the tiny adult male bolas spiders retain the juvenile hunting tactic of attracting psychodid flies, while female bolas spiders switch from hunting psychodid flies as spiderlings to hunting moths when the female spiders become older and larger. Received: 5 May 1997 / Accepted: 14 July 1997     

Advantages of social foraging in crab spiders: Groups capture more and larger prey despite the absence of a web

Among group‐living spiders, subsocial representatives in the family of crab spiders (Thomisidae) are a special case, as they build protective communal leaf nests instead of extensive communal capture webs. It could thus be inferred that antipredator benefits (e.g., enhanced protection in larger nests) rather than foraging‐related advantages (e.g., capture of more and larger prey) promote sociality in this family. Nonetheless, subsocial crab spiders do share prey, and if this behaviour does not reflect mere food scramble but has a cooperative character, crab spiders may offer insights into the evolution of social foraging applicable to many other cooperative predators that hunt without traps. Here, we performed a comparative laboratory feeding experiment on three of the four subsocial crab spider species—Australomisidia ergandros, Australomisidia socialis and Xysticus bimaculatus—to determine if crab spiders derive advantages from foraging in groups. In particular, we tested artificially composed groups of five sibling spiderlings vs. single siblings in terms of prey capture success and prey size preference. Across species, groups had higher prey capture success (measured in terms of capture rates and capture latency) and were more likely to attack large, sharable prey—dynamics leading to reduced food competition among group members in favour of living and foraging in groups. Within groups, we further compared prey extraction efficiency among the three applied social foraging tactics: producing, scrounging and feeding alone. In A. ergandros, individuals were exceptionally efficient when using the non‐cooperative scrounger tactic, which entails feeding on the prey provided by others. Thus, our multispecies comparison confirms foraging advantages in maintaining a cooperative lifestyle for crab spiders, but also demonstrates the relevance of research into exploitation of cooperative foraging in this family.     

Food imprinting and subsequent prey preference in the lynx spider,Oxyopes salticus (Araneae: Oxyopidae)

This object of this study was to determine if early feeding experience can affect subsequent prey choice in lynx spiderlings (Oxyopes salticus), and if so, is it evidence for food/olfactory imprinting. After emergence from the egg sac, three groups of 10 spiderlings were each fed exclusively for a 1-week period on one of three naturally-occurring prey species (crickets): group 1 fed on nymphs of Gryllotalpa hexadactyla; group 2 (Dialeurodes citrifoli); group 3 (Microcentrum rhombifolium). Following this, they were tested for subsequent prey preference in choice tests conducted in a plastic arena. Each spiderling was presented simultaneously with one individual of each prey species in a randomized design. Spiderlings exhibited a significant first preference for the original diet. Thus, experience with certain foods encountered by newly hatched spiderlings can affect subsequent prey preference in this species. Given the primacy of the early experience, the results are best interpreted in terms of imprinting and represent the first demonstration of olfactory imprinting in a spider.     

Interactions between citrus psylla,Trioza erytreae (Hem. Triozidae), and spiders in an unsprayed citrus orchard in the transvaal lowveld

During a two year survey, a total of 3,054 spiders represented by 21 families were sampled in an unsprayed citrus orchard in the Transvaal Lowveld. Numerically the Salticidae was the dominant family (34.4%) followed by the Theridiidae (21.9%), Thomisidae (11.9%), Araneidae (7.9%), Clubionidae (7.0%) and the Tetragnathidae (3.7%). Eighteen species of spiders were observed to prey on citrus psylla,Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), while six species trap nymphs and adults under their retreats and webs. There were significant positive correlations between the weekly psylla populations and the weekly populations of web-building spiders and wandering spiders present one to four weeks later but no significant correlation between the weekly spider populations and the weekly psylla populations present one to five weeks later. This seems to indicate that while spiders are unable to keep citrus psylla populations at acceptable low levels, they may contribute in reducing their numbers.      

Physiological and Biochemical Analysis to Reveal the Molecular Basis for Black Widow Spiderling Toxicity

The early research found that the spiderlings of black widow spider (Latrodectus tredecimguttatus) exhibited obvious toxicity to animals. The present work performed a systematical analysis of the aqueous extract of newborn black widow spiderlings. The extract was shown to contain 69.42% of proteins varying in molecular weights and isoelectric points. Abdominal injection of the extract into mice and cockroaches caused obvious poisoning symptoms as well as death, with LD₅₀ being 5.30 mg/kg in mice and 16.74 µg/g in Periplaneta americana. Electrophysiological experiments indicated that the extract at a concentration of 10 µg/mL could completely block the neuromuscular transmission in isolated mouse nerve‐hemidiaphragm preparations within 21 ± 1.5 min, and 100 µg/mL extract could inhibit a certain percentage of voltage‐activated Na⁺, K⁺, and Ca²⁺ channel currents in rat dorsal root ganglion neurons. These results demonstrate that the spiderlings are rich in neurotoxic components, which play important roles in the spiderling toxicity.     

真水狼蛛幼蛛各龄期的形态特征和生长发育

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

A mass rearing method for the linyphiid spider species Erigone atra (Blackwall) (Araneae: Linyphiidae)

Abstract:  A mass rearing method for Erigone atra (Blackwall) (Araneae: Linyphiidae) allowing continuous laboratory rearing is described. Twenty 1–2-day old spiderlings were kept together in plastic boxes, which were filled with soil containing a culture of the Collembola species, Lepidocyrtus lanuginosus (Gmelin) (Entomobryidae), and serving the spiders as a continuous available prey source. Once per week vestigial-wing fruit flies of Drosophila melanogaster Meigen (Diptera: Drosophilidae) were provided as additional prey. In addition, the rearing boxes were filled with wood-wool serving spiders as points of contact for their webs. After 3–5 weeks most of the spiderlings developed to adults, which were separated individually into glass tubes filled with soil and Collembola until all of them became adult. To produce a new generation of spiders 20–40 adult/subadult spiders originating from different mass rearing boxes were brought together and kept and fed in the same way as the spiderlings. Within a few days females started to produce eggsacs. The eggsacs were transferred into glass tubes filled with a layer of moist plaster of Paris until the spiderlings hatched, which were then bred as described above. Erigone atra was bred over 12 generations within a period of 2 years. The mean rearing success (from 1 to 2-day-old spiderlings to adults) was 59.3%. Decreasing rearing success, decrease of fecundity or decrease of adult spider size were not observed. Advantages and use of the mass rearing method are discussed in relation to rearing methods for other spiders.     

Kinship Influences Cannibalism in the Wolf Spider, Pardosa milvina

Recent studies have called into question the role of Wright's coefficient of relatedness (r) in the interactions among relatives. Kin selection theory predicts a positive relationship between relatedness and frequency of altruistic acts, but a number of researchers have reported the opposite relationship. I used a lycosid spider (Pardosa milvina) to test the hypothesis that genetic relatedness would affect the propensity of a cannibalistic species to prey on genetic relatives. I considered lack of predation to be a form of altruism where the predator incurs a cost (loss of a meal) that benefits potential prey. Specifically, I questioned whether direct genetic offspring would be avoided as prey items and whether the sex or reproductive condition of a cannibalistic predator would affect the likelihood of predation on conspecific juveniles. As predicted by kin selection theory, spiderling mothers ate significantly fewer of their own offspring than they did of nonkin spiderlings of the same age. Adult virgin female and adult male spiders ate significantly more spiders than females that had recently carried spiderlings. Females with egg sacs consumed significantly fewer spiderlings than did virgin female spiders. These findings support Hamilton's rule and suggest that, in some systems, genetic relatedness plays a strong role in governing altruistic behavior toward relatives.