Stano Pekár
Predation by arachnids
o True predators - catch and kill several animals throughout
their life (Araneae, Scorpiones, Solifuges, Thelyphonida,
Amblypygi, Schizomida, Ricinulei, Pseudoscorpiones,
Opiliones, Palpigradi, Gamasida)
o Scavengers – feed on prey remnants or dead animals
(Opiliones, Holothyrida, Opilioacaridae)
o Parasites - live in close association with a host
(Sarcoptiformes, Ixodida, Gamasida, Actinedida)
o Herbivores - feed on plants (Sarcoptiformes, Actinedida,
Opiliones)
Trophic categories
o majority arachnids are euryphagous
o Araneae, Scorpiones, Solifuges, Thelyphonida, Amblypygi,
Schizomida, Ricinulei, Pseudoscorpiones, Opiliones,
Palpigradi, Gamasida
Centruroides
Araneae Coleoptera
Hymenoptera Isopoda
Mantodea Orthoptera
Myriapoda Scorpiones
Nemastoma
Collembola Isopoda
Arachnida Oligochaeta
Diptera Gastropoda
Homoptera Psocoptera
Eremobates
Arachnida Coleoptera
Dipetra Lepidoptera
Hemiptera Blattodea
Orthoptera Vertebrata
Diet breadth
o prey availability vary with season and
habitat
o polyphagous predators switch to more
common prey or prefer certain prey
Diet of Micrathena in two habitats
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open shaded
Diptera Hymenoptera Coleoptera Homoptera
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spring summer autumn
Diptera Ensifera Heteroptera other
Diet of Pardosa during season
Prey availability
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prey size [mm]
frequency
Theridion Tegenaria
[17 mm][6 mm]
o prey size corresponds to spider’s size
o polyphagous species take small prey – smaller than prosoma
Prey size
o web builders
generally
capture larger
prey than
equally sized
hunting
spiders
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% spider body
%acceptance.
Salticidae, Ctenidae
Lycosidae, Philodromidae, Pisauridae, Theraphosidae
Thomisidae
Selenopidae, Oxyopidae
hunters
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Agelenidae,
Pholcidae
Scytodidae
Dipluridae
Araneidae
web-builders
o predation among guild members as a result of competition
o cannibalism (sexual, filial)
o Scorpions/spiders/solifuges in the desert (Polis & McCormick
1986) – removal experiment
o Scorpiones feed on spiders (8%) and solifuges (14%)
o Scorpions reduced density of spiders, not solifuges
Intraguild predation
Pauroctonus
Spring
Autumn
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Spiders Solifuges Spiders Solifuges
Control Removal
Density
Trophic
Specialisation
o evolved on dangerous, difficult, and abundant prey
o specialists are able to obtain all required nutrients from a single
prey type
o specialisation improves the efficiency of the prey capture and may
free the predator from the interspecific competition
specialists generalists
N = 37 296
Araneae
Mimetidae
o Araneophagous – Mimetidae, Palpimanidae
o Lepidopterophagous – some Araneidae
o Termitophagous – Ammoxenidae
o Crustaceophagous – Dysderidae
o Myrmecophagous – Zodariidae, some Theridiidae
Archaeidae
Ammoxenidae
49%
23%
12%
11% 1% 4%
ants spiders moths
termites flies woodlice
129 species
Araneae
o Ecological (short-term/local) – effect of time and habitat
o Evolutionary (long-term) – evolution of adaptations (psychological,
morphological, behavioural, physiological, venomic)
Euryphagous
generalist
Stenophagous
generalist
Euryphagous
specialist
Stenophagous
specialist
Pekár & Toft (2015)
Ecological dimension
Evolutionary
dimension
o innate olfactory preference in Euryopis spiders
o naïve spiderlings preferred cues from Messor ants
o older spiderlings on Drosophila diet switched their preference
Messor Myrmica Drosophila
Pekár & Cárdenas (2015)
Psychological
Preference of naïve spiders
Preference of older spiders
o Different chelicera shape in Dysdera
o used to catch woodlice
o Species with elongated chelicera used pincer strategy
o Species with flattened fangs used key strategy
o Species with concave chelicera used fork strategy
Dysdera
Řezáč et al. (2008)
Morphological
elongated
concave
flattened
o bolaso swinging in Mastophora to catch flying moths
o M. hutchinsoni captures predominanty two noctuid moth species:
Trichoplusia mynesalis and Lacinipolia renigera
o females produces allomone imitating the sexual pheromone of
moths to attract moth males
Behavioural
Eberhard (1980)
o prey processing in Palpimanus
o extracts all nutrients from spiders
o high performance on spider prey but poor on insect prey
Palpimanus
Pekár & Líznarová (2023)
Physiological
Survival on two diets
o potent venom of Zodarion is used to catch prey
o venom of euryphagous Cybaeodamus is similarly effective on
various prey
o Venom of Zodarion is only potent for ants, not on the
alternative prey
Zodarion
Michálek et al. (2019)
Venomic
Predatory guilds
o group of species (often closely related) exploiting the same
resources in a similar way
o Main classes: passive (sit-and-wait/ambush), intermediate
(stop-and-move), active (pursue)
o Passive: Pseudoscorpiones, Ricinulei
o Intermediate: Amblypygi, Thelyphonida, Schizomida, Palpigradi,
Scorpiones
o Active: Araneae, Opiliones, Solifuges, Gamasida
Time
Distan
ce
ambush
Stop-and-move
pursue
o using data on foraging strategy, prey range, vertical
stratification, and circadian activity (Cardoso et al. 2011)
o 111 spider families classified into 8 guilds
Sensing web
o retreat with signal threads, not used for prey capture but to
signal presence of a prey
o on the ground, under stones, on walls, in crevices
o when prey (crawling invertebrates) touches a thread, spider
darts forth to seize it
o Oecobiidae, Segestriidae, Filistatidae, Ctenizidae
Oecobiidae Segestriidae
Sheet web
o web with a tubular retreat at one end, and irregular threads
above
o built in vegetation
o spider runs on the upper surface of the web
o spider rests in the retreat, when prey stumbles over the
threads and falls into the sheet spider rushes out
o Linyphiidae, Agelenidae, Ammaurobiidae, Hahniidae, Dipuridae
Linyphia
Space web
o 3D web, hundreds of short zig-zag threads, some of them are
with gluey drops or cribellate silk
o capture prey crawling on ground or vegetation - prey gets
stuck, spider may throw more silk on the prey
o Dictynidae, Pholcidae, Nesticidae, Theridiidae
o horizontal or vertical 2D web catching flying prey mainly in the
night
o Uloboridae put cribellate silk, Araneidae & Tetragnathidae put glue
on the catching spiral
o entangled prey is quickly immobilised by wrapping or biting
o Araneidae, Tetragnathidae, Uloboridae
Orb web
Pasilobus
Cyrtophora
Scoloderus
Hyptiotes
o actively hunt prey on the ground or water
o agile hunters during the day or night
o overpower prey with legs or strands of silk
o Gnaphosidae, Clubionidae, Liocranidae, Lycosidae, Oxyopidae
Ground hunters
o Prey is immobilised by venom or silk (Beydizada & Pekár 2023)
o Dangerous (large) prey is immobilised by silk
o Bolder individuals use more frequently venom than silk
Conditional strategy
Drassodes
o capture prey on vegetation or ground
o prey is sized by outstretched forelegs that are stout and
elongated or small web that is held in forelegs
o Deiniopidae, Thomisidae, Sparassidae, Philodromidae
Ambush hunters
o actively search for prey on a flat surface during day
o orient towards prey, approach within a striking distance and leap
on it
o feed on flying or crawling insects
o Salticidae, Scytodidae
Other hunters
Predatory
behaviour
▪ Ethogram of prey capture
Prey capture
o spiders adjust their food selection to regulate intake of nutrients
(Mayntz et al. 2005)
o consume their prey based on their previous diet
o they either eat more of prey that is rich in nutrients they require or
extract specific nutrients from a single prey
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consumption(mg)
lipid-rich protein-rich
previous diet
protein diet
lipid diet
Consumption of different types of diet
Pardosa
Effect on predator
o Most arachnids have limited biocontrol abilities:
- limited functional and numerical responses, present intraguild
predation
o Mites (Phytoseiulus, Neoseiulus, Amblyseius) are used as
efficient biocontrol agents
o Cheyletus is used to control mite pests on stored grain (Cebolla
et al. 2009)
o it feeds on variety of mite pest species
Lethal effect on prey
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Controlefficacy
Predator density
Acarus Caloglyphus
Lepidoglyphus Tyrophagus
Cheyletus
o arachnids can also have non-consumptive effect on their prey
o presence of Tasmanicosa (glued chelicera) affected behaviour
of Helicoverpa - catterpilars spend less time on cotton leaves
(Rendon et al. 2016)
Non-lethal effect
Senses used
o vibrations are perceived through slit sensillae that form lyriform
organs (on legs)
o primary sense in all arachnids, mainly primitive hunters, tube
builders, signal-web builders and weavers
o web-builders have more slits than hunters
o sensitivity of slits increase with its length
20-120 μm long
Lyriform organs on a leg
A single slit
o slits detect the tiniest deformations of the skeleton, sensitive to
substrate-born vibrations (10-100 Hz)
o vibrations are not blocked by obstacles (visual or acoustic) or
blown away by wind
o spiders discriminate among types of vibrations: noisy irregular
signal are more effective than sinusoidal vibrations
Oscillograms and
frequency
spectra of
vibrations on
water
o acoustic signals are perceived by trichobothria on the dorsal
side of legs
o trichobothria are sensitive to air-born vibrations (50-150Hz)
o used mainly by hunters, net-casters, funnel weavers
o hunters have more trichobothria than web-builders (< 10/leg)
o trichobothria are feathery - increase the drag force and
sensitivity
o maximal distance eliciting predatory behaviour is 25 cm
Trichobothria on Ta
Anatomy of trichobothria
o interplay of trichobothria - Cupiennius turned toward the leg
stimulated earliest
o removal of 50% trichobothria from all legs → no behavioural
change
o removal of trichobothria on one side only → spiders turned at
correct angle but to other direction
o removal of trichobothria on forelegs → spider turned backwards
Attenuation of signals
in the air
o visual signals are perceived by eyes (ocelli)
o ME recognise shape and colour, LE are movement detectors
o prey is first detected by wide-angle lenses of LE, then fixed with
movable retina of ME
o narrow field of view is compensated for mobile eye tube of ME
o used by Salticidae, Lycosidae, Deinopidae, Sparassidae,
Thomisidae
o Cupiennius spiders has trichromatic colour vision
(UV+green+blue)
o spatial resolution of Portia AME is 6x worse than in human and
10x better than in dragonfly
o light sensitivity in Deinopis is equal to F=0.58 - better than any
camera lens
o Cupiennius eyes are sensitive enough even under moonlight
Salticid field of view
Spectral sensitivity of the Cupiennius
median eye
o chemical signals are perceived by chemoreceptors on distal
tips of tarsi
o chemoreceptors are inervated by 21 sensory cells
o little is known about chemoreception
chemoreceptor
o zodariid Habronestes bradleyi feeds on Iridomyrmex ants
o is able to identify alarm pheromone of the ants
o spiders locate patches where ant workers are engaged in
agonistic interactions
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number of ants
numberofspiders
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time(s)
alarmedant pheromone inactiveant control
Time spend by spiders in Y-maze arm
with different attractors
Relationship between the number
of spiders and ants engaged in
agonistic interactions
o predator imitates its prey (using
intra- or interspecific signals) in
order to approach the prey and
thus increase efficiency of capture
o UV is produced by sun - silk reflecting UV imitates open space
o primitive spiders (Mygalomorphs, Uloboridae) produce silk that
reflects UV light
o derived spiders (Araneidae) produce silk that exhibits low UV
reflectivity
o web decorations (stabilimentum) are highly reflective
o webs without stabilimentum captured 40% less prey than those
with stabilimentum
Cyclosa
o imitation of prey ensnared in the web
o Portia invades webs of other spiders
o after entering a web Portia vibrates with forelegs to produce:
- strong vibrations (imitation of ensnared insect)
- faint manipulation (prey contacting periphery)
- brief strong rocking (natural disturbance)
o after approaching the resident spider, Portia makes strong
manipulation if resident spider is large, and faint manipulations if
resident spider is small
Portia captures a theridiid
Records of simulated and Portia-made vibrations on web
o Cosmophasis spiders live close to and inside nests of Oecophylla
ants but avoid direct contact with the workers
o feed on the ant larvae not workers and lay eggsacs inside the
colony
o spiders steal larvae from an ant that is carrying them
Cosmophasis
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spider nestmate nonnestmate
Number
Number of aggressive behaviours of ants
Gas chromatogram of ants’ and spiders’
cuticular hydrocarbons
o spiders imitate cuticular hydrocarbons (mono- and
dimethylalkanes) of ants
o since spiders can penetrate other nests, the mimicking
hydrocarbons are rather species than colony specific
Zodarion
o Zodarion hunts ants outside their nests
o after capturing an ant, spider have to carry its prey
away from ants
o in order to avoid ants Zodarion tries to deceive ants by
„prey shielding”
Success: 80%
Formica (Ti)
38 hairs / 0.01 mm2
Zodarion (Ti)
8 hairs but 35 thorns / 0.01 mm2