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

Abstract

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

Geographic Variation in Reliance on Trial-and-Error Signal Derivation by Portia labiata, an Araneophagic Jumping Spider from the Philippines

Signal-generation behavior of Portia labiata, a web-invading araneophagic jumping spider (Salticidae), was investigated in the laboratory. Individuals derived from two habitats in the Philippines were compared: Los Baños, a low-elevation tropical rainforest site where prey (spider) diversity is especially high, and Sagada, a high-elevation pine-forest site where prey (spider) diversity is less. Maternal effects and variation in experience were minimized because all individuals tested were from laboratory rearing to second and third generation under standardized conditions. Individuals from both populations used a trial-and-error (generate-and-test) algorithm to derive appropriate aggressive-mimicry signals. However, in laboratory experiments, the Los Baños P. labiata relied on trial and error significantly more often than did the Sagada P. labiata. Selection pressures that may have been responsible for evolution of different levels of flexibility are considered, including the different arrays of prey to which the Los Baños and the Sagada P. labiata are exposed.     

Leaf hoppers of New Zealand: Subfamilies Aphrodinae,Jassinae, Xestocephalinae,Idiocerinae, and Macropsinae (Homoptera: Cicadellidae)

The cosmopolitan subfamilies Aphrodinae, Jassinae, Xestocephalinae, Idiocerinae, and Macropsinae are diagnosed and the New Zealand species described and illustrated. Each subfamily is represented in New Zealand by only one or two species, those in Idiocerinae having been introduced from Europe or North America. The species Euacanthella brunnea Evans (Aphrodinae) is synonymised with the Australian species E. insularis Evans (new synonymy).     

Predator–Prey Interactions Between Aggressive-Mimic Jumping Spiders (Salticidae) and Araneophagic Spitting Spiders (Scytodidae) from the Philippines

In Los Baños in the Philippines (Laguna, Luzon), Scytodes sp. indet. is a web-building spitting spider (Scytodidae) that preys primarily on jumping spiders (Salticidae) and Portia labiata is an aggressive-mimic jumping spider that preys especially frequently on Scytodes. Tactics by which three species of Portia (P. africana, P. fimbriata, and P. labiata) and, for Portia labiata, three disjunct populations (Sri Lanka and, in the Philippines, Sagada and Los Baños) capture this especially dangerous prey are compared. Local adaptation to Scytodes by the Los Baños P. labiata is discussed. The Los Baños P. labiata uniquely made consistent use of tactics (soft plucking with palps and signal–detour–leap sequences) that were apparently responsible for greater prey-capture success and more effective avoidance of being spat on. Inter- and intraspecific differences were evident despite having used Portia that were reared in the laboratory with no prioir experience with scytodids.     

Conditional strategies and interpopulation variation in the behaviour of jumping spiders

Abstract

Conditional strategies and interpopulation variation in the mating and predatory behaviour of salticid spiders are reviewed. A functional approach is adopted, and defended, in which specified behavioural phenotypes are accounted for, in large part, by specified selection factors. Courtship versatility, in which a male's behaviour depends on the female's maturity and location, is common in the Salticidae. If a male encounters an adult female in the open, where there is ample ambient light, he performs vision-dependent displays (Type 1 courtship) in front of her. If he encounters an adult female inside her nest, he uses different displays (Type 2 courtship) which are not vision–dependent and consist of various tugging, probing and jerking movements on the silk of the nest. These displays apparently send vibratory stimuli to the female. When a male encounters a subadult female inside her nest, he initially performs Type 2 courtship, then spins a second chamber on the nest and cohabits until the female moults and matures. A modification of optimal foraging theory has been used to examine factors that influence interpopulation variation in male courtship persistence. A study of five populations corroborated predictions from the model. Persistence appears to be related to female availability. Female availability is related to local phenology, which is, in turn, related to local climate. Complex examples of predatory versatility also have evolved in the Salticidae, especially in the genus Portia. All species of Portia studied are araneophagic spiders that invade other spiders' webs and practise aggressive mimicry. Portia fimbriata, uniquely among Portia species studied, uses specialised behaviour to prey on other salticids. Portia fimbriata and one of the salticids on which it preys, Euryattus sp., appear to be co-adapted to each other.     

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.     

Prey classification by an araneophagic ant-like jumping spider (Araneae: Salticidae)

What to attack is one of the most basic decisions predators must make, and these decisions are reliant upon the predator's sensory and cognitive capacity. Active choice of spiders as preferred prey, or araneophagy, has evolved in several distantly related spider families, including jumping spiders (Salticidae), but has never been demonstrated in ant-like jumping spiders. We used prey-choice tests with motionless lures to investigate prey-choice behaviour in Myrmarachne melanotarsa , an East African ant-like salticid that normally lives in aggregations and often associates with other spider species. We show that M . melanotarsa chooses spiders as prey in preference to insects and, furthermore, discriminates between different types of spiders. Myrmarachne melanotarsa 's preferred prey were juvenile hersiliids and its second most preferred were other salticids. To date, all documented examples of araneophagic salticids have been from the basal subfamily Spartaeinae. Myrmarachne melanotarsa is the first non-spartaeine and also the first ant-like salticid for which araneophagy has been demonstrated.     

Conditional use of honest signaling by a Batesian mimic

Jumping spiders (Salticidae) usually avoid ants, but some specieswithin this family single out ants as preferred prey, whileothers (especially the species in the genus Myrmarachne) areBatesian mimics of ants. Field records show that ant-eatingsalticids sometimes prey on Myrmarachne, suggesting that theunwanted attention of predators that specialize on the modelmay be an important, but poorly understood, cost of Batesianmimicry. By staging encounters in the laboratory between livingant-eating salticids and Myrmarachne, we determined that ant-eatingsalticids attack Myrmarachne. However, when Myrmarachne detectsa stalking ant-eating salticid early enough, it adopts a distinctivedisplay posture (legs almost fully extended, elevated 45°,and held out to the side 45°), and this usually deters thepredator. When Myrmarachne detects an ant-eating salticid beforestalking begins, Myrmarachne makes preemptive displays thatappear to inhibit the initiation of stalking. Using immobilelures made from dead Myrmarachne that were either in a displayposture or a nondisplay posture, we ascertained that specificallythe display posture of Myrmarachne deters the initiation ofstalking (ant-eating salticids stalked nondisplaying more oftenthan displaying lures). In another experiment, we ascertainedthat it is specifically the interjection of display posturethat deters stalking. When ant-eating salticids that had alreadybegun stalking experienced lures that switched from a nondisplayto a display posture, they stopped stalking. Although the unwantedattentions of its models' predators may be, for Myrmarachne,a hidden cost of Batesian mimicry, Myrmarachne appears to havean effective defense against these predators.     

The biology of Tauala lepidus,a jumping spider (Araneae: Salticidae) from Queensland: display and predatory behaviour

Abstract

The display and predatory behaviour of Tauala lepidus Wanless, an abundant salticid in north Queensland rainforests, was investigated in the laboratory and, to a lesser extent, in nature. T. lepidus leapt and walked into alien webs to catch spiders and insects, and was captured and fed on by other spiders. Females ate each other’s eggs. During intraspecific interactions, a complex repertoire of displays was used. Courtship versatility occurred, each individual male having a conditional strategy of different behaviours depending on whether the female is at or away from her nest, and whether she is adult or subadult. Yet other combinations of displays occurred during male-male and female-female interactions. Apparently, pheromones on nests and draglines of females released male courtship. Abdomen twitching, a behaviour common to the display repertoires of many salticids, was an especially complex and pervasive behaviour of T. lepidus. T. lepidus also twitched its abdomen when it contacted alien webs and preyed on other species of spiders. The behaviour of T. lepidus is compared to that of Jacksonoides queenslandica Wanless, a species from the same group (Astieae).     

Factors affecting use of mirex‐poisoned protein baits for control of European wasp (Paravespula germanica) in New Zealand

A bait of canned fish poisoned with 0.5 % or 1 % mirex substantially reduced populations of the European wasp, Paravespula germanica (Fab.), in a part‐cleared, part‐forested resort area in the Marlborough Sounds. In separate baiting regimes, bait was taken for as long as 9 weeks when 0.5% formulation was offered from 5 stations, but when 1 % formulation was offered from 10 and from 15 stations the time was reduced to 5 weeks and 4 weeks respectively. Synthetic and extracted materials tested as baits were unattractive to wasps, but fish baits attractive when fresh could be freeze‐dried without loss of acceptability. Marked wasps were caught up to 1200 m from their nests, and in the control programme 64 ppm mirex was recovered from dry brood comb of a defunct nest 700 m from the nearest bait source. The importance to bait control programmes of data on flight distance and foraging habits, and of the winter survival of colonies with prolonged queen production, is discussed. Some observations on reproductive biology are made in an appendix to the paper.     

Larval development of the cockle Chione stutchburyi (Bivalvia: Veneridae) reared in the laboratory

Abstract

Larvae of the New Zealand cockle Chione stutchburyi (Wood, 1828) reared to settlement in the laboratory are described. They are characterised by dissimilar shoulders with a large, broadly rounded anterior shoulder and end, and broadly rounded umbo, typical of the Veneridae. Setting occurred after 20 days at a minimum length of 180/µm. Shell dimensions increased linearly during larval development but hinge length did not. The L:H ratio decreased from 1.27 at L = 100 to 1.1 at L = 200 and the L:D ratio from 1.95 at L = 100 to 1.59 at L = 200. An SEM study revealed that the larval hinge is characterised by a toothed provinculum forming a broad medial projection on the right valve, opposing two projections on the left valve. Conspicuous flanges on the anterior and posterior shoulders of the left valve fit into corresponding grooves of the right valve.     

Vision-based innate aversion to ants and ant mimics

Innate vision-based aversions to model and mimic were investigatedusing a mimicry system in which the models were ants (Formicidae),and both the mimics and the predators were jumping spiders (Salticidae).Jumping spiders are a large group of predatory invertebratesthat usually prey opportunistically on prey of similar size.We used 12 representative species from this group, the "ordinarysalticids" as predators. The mimics considered belonged to anothergroup, salticids that resemble ants. A choice arena containingan empty chamber and a stimulus chamber was used for testingpredator responses to a variety of dead arthropods (ants, antmimics, and an array of non–ant-like species) mountedin a lifelike posture. When presented with visual cues fromarthropods other than ants or ant-like salticids, naive predatorschose the empty chamber no more often than the stimulus chamber.However, when visual cues were from ants or from ant-like salticids,ordinary salticids chose the empty chamber significantly moreoften than the stimulus chamber. These findings suggest learningby the predator is not necessary in order for ant-like salticidsto gain Batesian mimicry advantages.     

河内蚁蛛雌性记述(蜘蛛目,跳蛛科)

首次发现并报道了采自云南的跳蛛科蚁蛛属河内蚁蛛Myrmarachne hanoii,Zabka,1985的雌性个体。为我国新纪录种。文中详细描述了本种雌性个体的特征及与其近似种的比较,同时附有特征图。研究标本保存于湖南中医药大学。     

中国蚁蛛属一新种记述(蜘蛛目:跳蛛科)

记述了我国蚁蛛属1新种：短螯蚁蛛Myrmarachne brevis sp.nov.,标本采自云南景洪和广西北海,保存在白求恩医科大学生物教研室和湖南中医学院生物教研室。正模测量如下（单位：mm),体长6．82,头胸部长3．05,腹部长3．50,眼区长1．26,第1眼列宽1．45,第3眼列宽1．50,头胸部背面棕红色,眼周围黑色,眼区中央有1对短棒状黑褐斑,螯肢较短小,触肢器圆饼状,贮精囊如“C”型弯曲的肠管状。     

Dynamics of the evolution of Batesian mimicry: molecular phylogenetic analysis of ant-mimicking Myrmarachne (Araneae: Salticidae) species and their ant models

Batesian mimicry is seen as an example of evolution by natural selection, with predation as the main driving force. The mimic is under selective pressure to resemble its model, whereas it is disadvantageous for the model to be associated with the palatable mimic. In consequence one might expect there to be an evolutionary arms race, similar to the one involving host-parasite coevolution. In this study, the evolutionary dynamics of a Batesian mimicry system of model ants and ant-mimicking salticids is investigated by comparing the phylogenies of the two groups. Although Batesian mimics are expected to coevolve with their models, we found the phylogenetic patterns of the models and the mimics to be indicative of adaptive radiation by the mimic rather than co-speciation between the mimic and the model. This shows that there is strong selection pressure on Myrmarachne, leading to a high degree of polymorphism. There is also evidence of sympatric speciation in Myrmarachne, the reproductive isolation possibly driven by female mate choice in polymorphic species.     

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.