• Insectivorous plants • Parasites (Nematodes, Acari, Neuroptera) • Parasitoids (wasps, flies) • Predators (Arachnida, Insecta, Pisces, Amphibia, Reptilia, Aves, Mammalia) Arachnid orders Predatory groups Proportion of arachnid enemies Pekar& Raspotnig (2022) Pompilid wasp Toft & Rees (1998) • Vespulo vulgaris is an important predator of invertebrates in New Zealand • probability of spiders' (Eriophoro) survival was negatively correlated with wasp abundance • more spiders survived in the area with reduced wasp abundance than in the control area Spiller & Schoener (1988) • Bahamian islands without lizards have higher densities of spiders • removing lizards increased the average number of spiders by three-fold Impact of lizards on the density of web-building spiders Rypstra (1984) • survival of spiders in tropical regions was higher when they were protected by cages that excluded vertebrates (birds, primates) • Cages did not prevent movement of spiders and their prey Impact of birds on disappearance of web-building spiders morning afternoon Multiple defences • Each species evolved suite of defences used - at different stages of attack by a single predator - against different predators Frequency-dependent selection - the fitness of a phenotype as it depends on the composition in a population Positive - gives an advantage to common phenotypes Negative (apostatic) - advantageous for rare forms Primary defences Ruxton et al. (2019) • prevent detection • operate before a predator initiates prey-catching behaviour • anachoresis, background matching, disruptive colouration, countershading, transparency ■ Anachoresis ■ Crypsis ■ Aposematism ■ Batesian mimicry ■ Masquerade Pekar& Raspotnig (2022) Secondary defences • operate after detection to avoid attack - function to reduce probability of capture • secondary defences, warning displays, Mullerian mimicry Other defences • to mislead predators • Batesian mimicry, camnouflage, startle, deflection, thanatosis B ■ Chemical ■ Mechanical ■ Stratle ■ Deflection Thanatosis ^^^^B • to stay out of predator's environment • hide under bark (Pseudoscorpiones), in caves (Amblypygi), under stones (Ricinulei), in burrows (Scorpiones, Solifugae), in retreats (Araneae) Manicom et al. (2008) • manipulative experiment to assess the effectiveness of self-made shelters • exposed (without shelters) vs. sheltered spiders • exposed spiders were more negatively affected by lizards than sheltered ones near to the ground rgiope Cyrtophora LU +i Q. (0 n a) 5 o E 50-, 40-30" 20" 10-0- □ Predatory lizards ■ excluded □ included 0 □ □ in E S <1 E S 1-20 E S 21-40 E S 41 + Web spiders Exposed or Sheltered Height above ground (cm) • resembles the colour, pattern, and lightness of background • used by diurnal species employing sit-and-wait foraging strategy • species move slowly, stealthily or rapidly • used by almost all orders Costs: • investment into pigmentation • reduced opportunities in foraging, mating, thermoregulation • restricts occurrence of spiders to a certain microhabitat Messas et al. (2014) Background selection • passive or active selection of a background or change colour • araneid Eustolo perfido • most frequent on trees covered by mosses and lichens • motionless during day and foraging and web-building during night smooth lichen moss lichen+moss Bark type Colour polymorphism Schaller & Kohler (2008) • maintained by apostatic selection due to formation of a search image in predator • melanic forms of Neottiuro predominated in polluted habitat • after habitat regeneration darker individuals increased in abundance • colouration creates false boundaries - some body parts are more discernible than others • can be independent of background • in ground and vegetation dwelling arachnids • used by Acari, Araneae, Opiliones, Scorpiones, Solifuges Costs: • as in background matching • colouration of an arachnid cancels its shadows • surface exposed to light is darker than the opposite surface • independent from background, diurnal activity in open habitat • used probably by Opiliones and Araneae Costs: • thermoregulation • exposure to predators 75 • blends with background - typically in water due to similar light refraction conditions • whole body (all organs) is transparent • used by water mites Costs: • minimise consumption • deployed during/before contact with predator - reduce probability of capture • chemical, mechanical, behavioural Benefits: • predators learns more quickly Costs: • reallocation energy to produce defences Evolutionary models • Kin selection - aggregated defended individuals, killing few individuals will prevent attack on kins • Individual selection - an individual will survive attack, provide protection for itself (thick cuticle) production of toxins, irritating repellents (volatile compounds) venom glands-Araneae, Scorpiones, Pseudoscorpiones exocrine glands - Opiliones, Acari, Thelyphonida, Schizomida Irritant/repellent chemicals • hydrocarbons, terpenes, aromatics - Astigmatid mites • quinones, phenolics, acyclic ketones - Opiliones • carboxylic acids - Thylephonida, Schizomida Poisons • hydrogen cyanide, alkaloids - Oribatid mites • nicotine, anabaseine - Opiliones Pheromones • Alarm - Opiliones Machado etal. (2005) • release droplets from tubercles • secretion diffuses, covers harvestmen body, sprayed or transferred to the enemy by legs • benzoquinones prevent approach by predators - chemical shield • benzoquinones treated prey was rejected by ants, spiders, frogs sac-like glands on metasoma vaporised spray to a big distance acetic acid, ketones, esters repelled Solifuges, mice, shrews, racoons Schmidt et al. (2000) glandularia of water mites produce proteinaceous substances repellent against fish „ . , K b Kerfoot etal. (1980) Mastigoproctus Limnochares Heethoff et al. (2011) • paired oil glands in opisthosoma of Oribatid and Astigmatid mites • produce diversity of substances - hydrocarbons, terpenes, aromatics, and alkaloids • function as alarm pheromones • beetles rejected mites with full glands I 6(1 Oribotritia • spines - Opiliones, Araneae, Acari • urticating hairs - Araneae - effective against badgers, skunks, racoons • strong cuticle - Acari, Araneae - effective against beetles (Heethoff et al. 2018) • silk-Araneae - effective against arthropod and vertebrate predators (Vetter 1980) Nasua aggressive stance, counterattack- Araneae, Scorpiones, Solifuges, Thelyphonida, fleeing, dropping-Araneae, Pseudoscorpiones, Opiliones freezing-Araneae, Opiliones Cyrtophora Vs.- mygalomorph Mastigoproctus • in species with effective secondary defences - potent venom, spines, hard cuticle, chemicals • advertised by a visual, acoustic or chemical (aposematic) signals • visual signals - always on, used during day, perceived at longer distance • acoustic and chemical signals - deployed after attack, used during night, perceived at short distance • signal is conspicuous against background - contrasting colours, deterring sounds and chemicals Benefits: • unconstrained opportunities Costs: • production of the signal Pomini et al. (2010) • visual signals - used by Opiliones, Araneae, Acari • acoustic signals (stridulation) - used to advertise chemical defences in Opiliones, urticating hairs in spiders • aposematic colouration evolved from cryptic in species with defences (pre-adaptations to defences) • followed by shift in habitat preference Kerfoot (1982) • wasps avoided Microtheno spiders due to hard cuticle • fish rejected water-mites (produce mucus-like substance) • in food Brandley et al. (2016) • American Latrodectus species differ in red colouration on abdomen • defended by sticky silk and powerful venom • ventral red marking is conspicuous to birds • birds attacked more dummies imitating completely black than red species ventral d< H'sul wr wT "w W 0.5 0.4 5 mm • related or unrelated species sharing similar aposematic signal • form Mullerian rings • unpalatability vary within rings • all species share costs of predator learning - minimised by increasing species number • absence of polymorphism due to frequency-dependent selection • possibly used by Acari, Araneae, Opiliones • in Malaysia - several species of spiny spiders with sympatric distribution Actinocantha globulata G hasselti Gasteracantha diardi (£)A|©4 Wild al«xanaerwildxom • imitation of low-profitable (noxious, unpalatable, toxic) model by palatable species • imitation of aposematic signal (visual, acoustic, olfactory) • Resemblance is multi-trait - colouration, shape, size, behaviour, ecology • mimics parasite on models • used by Araneae and Solifuges Models of mimetic spiders 5% 3% 78% □ ants □ flies □ bugs □ mutilids ■ beetles □ othe Paraplectena - ľlaskrecki / Mir"1 solpugid Myrmecomorphy • defended (bite, sting, communal attack, formic acid, hard integument, spines) • numerous and occur in many habitats • similar morphology (body size, wingless) Morphological resemblance • 3 body parts - head, thorax, gaster • presence of antennae • 3 pairs of legs Behavioural resemblance • Circadian activity, locomotion, legs movement Shamble etal. (2017) • Myrmorochne walks on 4 legs, wave forelegs only when stationary • exhibited winding trajectory similar to ants • spiders pounced on payback of ant-mimics less than on spiders (a) • Frequency-dependent selection - rate of predation on mimics depends on the relative abundance of models and mimics: the more models the less attacks on mimics Ramesh et al. (2016) birds, lizards, wasps, spiders avoided to catch ant-mimics mantids have innate aversion to ants - avoid to catch ant-mimics too B 50 -i 45 - in 40 - -f-,rJ C n 35 - E 30 ■ tn 25 - u r 20 15 - 10 - — 5 ■ 0 - Camponotus Myrmarachne Carpenter ant Carpenter ant-mimic Nonmimic Mimetic accuracy • Accurate mimics - imitate all traits • Inaccurate mimics - imitate size and colouration Evolutionary models • Multi-model hypothesis: resemble more than one model inaccurately - can co-occur with all models • Multi-predator hypothesis: accurate mimicry will evolve if the selection from visually-oriented predators is strongest, inaccurate mimicry will evolve if selection from other types of predators is strongest • Noxiousness hypothesis: accurate mimics resemble less defended species than inaccurate mimics • Relaxed selection hypothesis: predators do not perceive details of resemblance Edmunds (1993) • Pison wasps are spider parasitoids • of 873 spiders in wasp cells 870 were salticids • wasp take fewer ant-mimics than non-mimics • wasp do not forage near ant nests Abundance of good/poor/non-mimics in the wasp cells and in the field good poor non Pekaret al. (2020) • acoustic signals are important at low-light conditions • Polpimonus spiders co-occur with mutillid wasps under stones • Polpimonus spiders can fall prey to nocturnal predators • mutillids are defended by powerful sting and strong cuticle • Polpimonus is palatable • both use defensive stridulation of similar characteristics • Eusparassus spiders and geckoes avoided mutillids • Eusparassus spiders attacked Palpimanus at lower frequency than control • geckoes attacked but dropped stridulating spiders • stridulation protects Palpimanus from nocturnal predators Sham-operated Silenced Control Wasp Sham-operated Silenced Control Wasp Putptmanus _ Palptmaaus • imitation of inedible objects (bud, branch, seed, flower, poo) • imitated objects are extremely common • do not imitate signals (aposematic) but cues • resemblance is multi-trait - visual and chemical cues • effective for sit-and-wait strategy, often have nocturnal activity • used by Opiliones and Araneae Liu et al. (2014) • Cyclosa ginnaga on the stabilimentum resembles a bird-dropping • spectrometric profiles were similar between spiders and bird droppings • signals (acoustic, visual) produced after attack by undefended prey • signals are hidden and triggered by predators • after display prey relies on fleeing or hiding • stimulates predator's sense to delay subjugation • used against rare predators • used by Acari, Amblypygi, Araneae, Opiliones, Scorpiones, Solifuges Visual displays • posture displays (increase body size)^B • aposematic markings underneath • body jerking (difficult to focus) Acoustic display • stridulation (disturbance) Phoneutria Pholcus {BSlttHEGftaD prey influences position of the initial contact of the predator to decrease risk of harm (chance of escape) based on sensory exploitation of predator's perception in the form of appendotomy: - Autotomy - reflex action - Autotilly - self-removal - Autospasy - restrained by extranal force detached lesg/telson may twitch used by most orders Costs: • some body part is sacrificed - it might/not be regenerated Philodromus ■\WBffi) • adoption of an immobile state reminiscent of dead animal • reduces risk of detection/capture after primary detection • last-resort defence alike fleeing, counter-attack • remain in thanatosis for few minutes • used by Acari, Opiliones, Ricinulei, Araneae Costs: • loss of opportunities Latrodectus Hoplobunus