OHIO STATE UNIVERSITY EXTENSION
AGRICULTURE AND NATURAL RESOURCES FACT SHEET
ENT-70-15
Ohio’s Natural Enemies: Crab Spiders
Order: Araneae, Family: Thomisidae
Mary M. Gardiner, Department of Entomology, and Mary Griffith, Ohio State University Extension
Overview
Crab spiders are commonly found in home gardens
and landscapes. They are generalist predators, meaning
they feed on a diversity of arthropods. Crab spiders can
be contributors to biological control, where feeding by
natural enemies results in a reduction of pest populations. In addition to hunting insects, they also feed on
pollen and even nectar. Growing a diversity of flowering plants will provide spiders with protein and sugar,
to sustain them in times of low prey availability. Also,
avoiding the use of broad spectrum insecticides such as
pyrethroids or carbamates is advised to promote crab
spider populations and encourage biological control
in the garden.
Identification
Like all arachnids, crab spiders have a two-segmented
body consisting of a prosoma (cephalothorax) and an
opisthosoma (abdomen). They have four pairs of legs
and one pair of pedipalps on their prosoma. Pedipalps
are short appendages near their chelicerae, or mouthparts, which serve sensory functions, assist with prey
capture and feeding and are even utilized in mating.
Crab spiders get their name from their crablike
appearance, and their ability to walk sideways. They
are small- to medium-sized spiders, with a body length
of 2-11 mm. Their body is somewhat flattened and they
have stout robust legs. A crab spider’s front two pairs
of legs are longer than the third and fourth pairs. They
have eight relatively equally sized eyes.
Feeding and Habits
A crab spider’s relatively small eyes can only detect
prey at very close distances, but they can detect motion
up to 20 cm away. Crab spiders are sit-and-wait predators, meaning they hunt motionless until a potential prey
item comes within their grasp. Crab spiders capture
their prey with their front two pairs of legs and bite
it, injecting venom to paralyze their meal. The use of
Like all spiders, Thomisidae have two body regions, a
prosoma and an opisthosoma. They have four pairs of legs,
pedipalps, eight eyes, and chelicera on their prosoma. The
opisthosoma or abdomen includes the lung slits (for breathing), spinnerets (to produce silk) and the epigastric furrow
which houses the internal reproductive organs. Females also
have an epigynum, an external reproductive structure that
accepts sperm from the male’s palp during mating (Photos:
John Maxwell: full body; and Iustin Cret: eyes and abdomen).
Prosoma
Opisthosoma
Pedipalp
Leg 4
Leg 1
Leg 2
Leg 3
Median eyes
Lateral
eyes
Lateral
eyes
Chelicerae
Epigyum
Lung slit
Spinnerets
Lung slit
Epigastric furrow
extension.osu.edu
agnr.osu.edu
Ohio’s Natural Enemies: Crab Spiders—page 2
venom to cause paralysis allows crab spiders to capture
and consume even large insects. The hunting ground
of crab spiders varies among species. They may hunt
on the soil surface, leaf litter, mulch, trees and shrubs,
or garden plant leaves, stems or flowers. Crab spiders
do not build webs, but do use silk to attach drop lines
to vegetation. If the spider becomes dislodged when
attempting to capture a meal it can use the drop line to
climb back into position. Crab spiders feed on a diversity of other arthropods including insects considered
garden pests, but also beneficial insects such as bees
and other spiders.
Life Cycle
When they reach the adult stage, male crab spiders
must locate a reproductive female. It’s not fully understood how males find their mate, but they may use airborne pheromones or visual cues, and some species are
known to follow drop lines left by other spiders. Once a
male locates a female, courtship and potentially mating
will follow. In some species this courtship includes the
male covering the female loosely with strands of silk;
this does not restrict her movement and is thought of as
a form of courtship—referred to as a bridal veil. Spiders
do not mate directly like insects do. Instead the male
deposits sperm onto a small web he constructs specifically for this purpose; he then uses his pedipalp to take
up the sperm from the web and store it. He will then use
his pedipalp to inseminate the female. When ready to
lay her eggs the female will find a protected location,
or create one using silk to roll a leaf into a protective
structure. She will guard her eggs until they hatch. Crab
spiders develop via gradual metamorphosis, meaning
they hatch from an egg and undergo several molts as
a juvenile before eventually becoming a reproductive
adult without entering a pupal stage. Most crab spiders
species will have one generation per year in Ohio. They
overwinter as either eggs or immatures.
This white banded crab spider snacks on pollen as it awaits a
possible insect meal with its front two pairs of legs outstretched
(Photo Kim Moore).
Crab spiders mating. Males are often smaller and can differ in
coloration from females (Photo: MaLisa Spring).
The hunting spot selected by this northern crab spider,
Mecaphesa asperata, is somewhat precarious. This spider has
attached a drop line; if it is dislodged during prey capture it can
regain its position and try again (Photo: Dan Leeder).
A female Xysticus stands guard, protecting her egg sac against
any potential egg predators (Photo: Roberta Gibson).
Ohio’s Natural Enemies: Crab Spiders—page 3
Common Crab Spiders
Approximately 30 species of crab spiders have been
documented in Ohio. Several species of crab spiders in
the genera Xysticus and Ozyptila can be found, which
range in color from light grey to dark brown and black
and blend in well with mulch, soil and leaf litter. The
bark crab spider, Bassaniana versicolor, has a mottled
brown to black coloration that camouflages this spider
well. Species that use flowers as hunting grounds tend
to be brightly colored to blend in with their surroundings. The goldenrod crab spider, Misumena vatia, and
white banded crab spider, Misumenoides formosipes,
are even able to change color from white to yellow in
response to the color of the flowers it is hunting within.
These spiders produce pigments called ommochromes,
which catalyze this color change in an outer layer of
cells on their bodies. Changing color happens within
just a few days, and the spider is able to change back
to its white coloration as well.
Using pigments it produces, the goldenrod crab spider,
Misumena vatia, is able to change from white to yellow. This
cripsis may increase a spider’s hunting success within flowers,
and/or protect it from its own predators such as wasps and birds
(Photo: Peter Hollinger: yellow; and Charley Eiseman: white).
References
Several genera of crab spiders including Xysticus (top) and
Bassaniana (bottom) have a mottled brown, grey and/or black
coloration that camouflages well with tree bark, soil, mulch and
leaf litter where these species hunt (Photos: Xysticus: Harvey
Schmidt; Bassaniana: Carol Davis).
Anderson, J.T., and D.H. Morse. 2001. Pick-up lines:
Cues used by male crab spiders to find reproductive
females. Behavioral Ecology 12: 360-366.
Bradley, R. 2015. The provisional list of Ohio spiders.
osumarion.osu.edu/SpiderWeb/provisional_spider_
list.pdf
Gardiner, M.M. 2015. Good Garden Bugs. Quarry Books.
Beverly, Massachusetts. 176 pages.
Kaston, B.J. How to Know the Spiders. 1953. W.M. C.
Brown Company Publishers. Dubuque, IA. 220 pages.
Pollard, S.D., M.W. Beck, and G.N. Dodson. 1995. Why
do male crab spiders drink nectar? Animal Behaviour
49: 1443-1448.
Robinson, M.H. 1982. Courtship and mating behavior
in spiders. Annual Review of Entomology 27: 1-20.
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