A M . ZOOLOCIST, 9:133-144 (1969).
A Spider's Vibration Receptor: Its Anatomy and Physiology
CHARLES WALCOTT
Department of Biological Sciences, State University of Nexu York
at Stony Brook, N. Y. 11790
SYNOPSIS. The common house spider, Achaearanea tepidariorum, has a sensitive
vibration receptor on each of its eight legs. This receptor is the tarso-metatarsal
lyriform organ, and while it may not be the only vibration receptor the spider has, it
appears to be the most sensitive. The 10 receptor units of which the sense organ is
composed are all sharply tuned to specific frequencies between 60 and 1400 cps, but
the sensitivity of each receptor unit depends upon the tension of the slits of the
lyriform organ. Physiological experiments have shown that the tuning of the receptors
occurs only in response to air-borne sound; no discrimination is made of frequencies of
web-borne vibration. One can speculate that the high sensitivity to air-borne
sound is a consequence of the relatively poor transmission of vibration through
Achaearanea's web.
Most species of spiders are literally covered with "lyriform" organs—sensory organs containing slits. The common house
spider, Achaearanea tepidariorum, has a
set of lyriform organs near the tarsometatarsal joint on each of its eight legs.
This organ is larger than those elsewhere
on the spider's body, and the slits are oriented at right angles to the long axis of the
leg.
There have been many speculations
about the function of the lyriform organs.
They have been thought to act as detectors
of smell, temperature, taste, chemoreception, or leg position. (Gaubert, 1892;
Mclndoo, 1911; Vogel, 1923; Kaston, 1935;
Millot, 1949). It has probably been a mistake to assume that all these sense organs
serve the same function. Pringle (1955)
has shown that the lyriform organs of scorpions act as stress receptors in the cuticle
much like insect campaniform sensilla. But
it appears that the lyriform organ at the
tarso-metatarsal joint in Achaearanea is especially modified to respond to vibration.
This does not mean that the lyriform organ is the only vibration receptor Achaearanea has; many of the Trichobothria also
The research reported here was supported by
contracts between Cornell University and The
Office of Naval Research, Nonr 140-117; between
the Quartermaster Corps, U. S. Army and Harvard
University, Dal9-129-QM1428; and by contract
Nonr 1866 (46) and Nonr 3225 (00) between The
Office of Naval Research and Harvard University.
respond to air-borne sound. But the intensity of sound needed to elicit a response
from them is so much greater than that
needed to stimulate the tarso-metatarsal
lyriform organ that I suspect, in Achaearanea at least, the lyriform organ provides
the most information. This paper will
summarize some of our observations on the
anatomy of the receptor, the information
the receptor provides, and the relationship
between the spider's behavior and the
properties of its vibration receptor.
ANATOMY
The anatomy of the tarso-metatarsal
lyriform organ has been examined by
Salpeter and Walcott (1960) and Walcott
and Salpeter (1966). Figure 1 is an artist's
reconstruction of serial sections made with
the electron microscope. Figure 2 is a photograph of a lyriform organ from the tibia
of Achaearanea. Clearly there is a profound difference in the microscopic anatomy of the two sense organs. In the metatarsal lyriform organ the nerve cell process
ends on the side of the cuticular lamella;
in the tibial organ it ends on the inner
membrane of the slit. In addition the
metatarsal slits are much wider than those
on the tibia. The tibial sense organ is, in
many respects, reminiscent of the insect
campaniform sensilla; Pringle (1955) has
shown that in scorpions the lyriform or-
133
1S4
CHARLES WALCOTT
FIG. 1. Inset: Surface view ot the lyriform organ
located at the tarso-metatarsal joint o£ Achaearanea. The lyriform organ in this photograph shows
only nine slits; others may have up to 11. The
slits are oriented at right angles to the leg.
Drawing: An artist's reconstruction of the lyriform organ, made from serial sections viewed with
the electron microscope, to show the basic structure common to all the slits of the vibration
recejjtor. Each slit forms an outer chamber (c) in
135
VIBRATION RECEPTOR OF SPIDER
the cuticle bounded by an outer (o) and inner (i)
membrane and two cuticular lamellae (L). A
vessel (v) attached to the inside of the inner
membrane forms a bulge into the interior of the
leg. A dense-walled tubule (T) runs through the
vessel (v) and through an opening in the inner
membrane (i) to attach to the side of the cuticular
lamella (L). The tubule itself is an extension
of the neurilemma (n) which surrounds the axis
cylinder from a bipolar sense cell (N) that is
situated some distance up the leg. The axis cylinder terminates as an end bulb (B) near the bulging
vessel, and a thin filament (F) arises within
the end bulb, runs into the tubule (T), and is
carried with it to the point of attachment. An
outer sheath cell (S) surrounds the combined
structure of tubule and vessel. (From Salpeter and
Walcott 1960).
gans are proprioceptors responding to
stresses in the cuticle. This leads us to the
speculation that the metatarsal lyriform
organ is simply a modification of these
more common lyriform organs, and that
the modifications we see are responsible for
the great sensitivity to small cuticular distortions over a very wide range of frequencies.
The microscopic internal anatomy of the
metatarsal lyriform organ is quite complex. The organ is composed of approximately ten parallel slits each one of which
is innervated by a single bipolar sensory
cell. The distal filament of the nerve cell
attaches to the wall of the slit at its widest
part, and, looking at a surface view of the
slits, it is evident that this wide portion of
the slit is staggered around the circumference of the leg. Whatever the reason for
this staggering, it means that any single
section through the receptor shows different aspects of the different slits much as
one might see in serial sections.
The slits are bounded on both the outer
and inner sides with a cuticular membrane. The space between the two membranes appears to be fluid-filled. A process
from the nerve cell extends to an end bulb
which in turn gives rise to a filament
which, passing through an elaborate series
of vessels, attaches to the wall of the slits.
How the various anatomical features of the
receptor detect sound is largely unknown.
It is clear that only the compression of
the slits leads to excitation, but where and
how this compression leads to the generation of nerve impulses is not known.
One way of investigating this question is
to examine the changes in the anatomy
and physiology of the receptor when the
spider molts. Because the lyriform organ is
an integral part of the cuticle, every time
the spider sheds, it must regenerate its vibration receptor. If the regeneration were
gradual, one might correlate changes in
the physiological properties of the receptor
with changes in its morphology (Fig. 3).
Unfortunately, the old vibration receptor
remains functional until at most a few
hours before the shedding of the cuticle.
When the cuticle is shed, the new vibration receptor becomes functional within a
few minutes. Thus the only physiological
change seen in some spiders is a decreasing
sensitivity to sound as the molt approaches,
followed by full sensitivity after shedding
the old cuticle (Walcott and Salpeter,
1966). The relationship between the physiology of the receptor and its anatomy is
still unclear.
PHYSIOLOGY
The sense organ is composed of about
ten parallel slits each innervated by a single nerve cell. By recording from the sensory nerve and using a pulse height analyzer (Littauer and Walcott, 1959) we
can follow the activity of a single receptor
unit. The isolated spider leg was rigidly
mounted in a lucite chamber and the action potentials recorded with a sharpened
tungsten wire inserted through the cuticle.
The electrodes and leg were mounted in
such a way that vibrations of the electrodes
did not excite the receptor, but the tip of
the leg and the lyriform organ extended
into free space. The experiments were conducted in a variety of enclosures including
the anechoic chamber in the Crufts Laboratory at Harvard University. There were
no significant differences in the responses
to air-borne sound in any of these cham-
136
CHARLES WAI.COTT
^'^WL^
/
FIG. 2. An electron micrograph of the tibial lyriform organ on Achaearanea. The arrow points to
the attachment between the terminal filament and
the outer membrane. T, tubule; F, filament which
runs between the outer membrane and the bipolar
sense cell.
VIBRATION RECEPTOR OF SPIDER
IS?
bers as long as adequate provisions were
made to eliminate reflections of sound
from the chamber walls and thus standing
waves. Sound pressure was measured with
a calibrated microphone and is given here
in db re 0.0002 dyne/cm2. For further details, see Walcott and Van der Kloot
(1959) and Walcott (1963).
If one measures the sound pressure
necessary to elicit a response of five action
potentials per second from a single receptor unit, one finds great variation from one
frequency to another. Figure 4 shows that
one receptor had a maximum sensitivity
at 102 cps but was relatively insensitive at
other frequencies. At frequencies above 1.5
kc the receptor again became sensitive.
Another receptor unit in the same preparation had its lowest threshold at 215 cps,
and a third at 78 cps. As far as we can tell,
FIG. 3. The lyritorm organ being developed in the
new cuticle about 6 '/£ hours prior to the shedding
o£ the old cuticle. Notice the nerve filaments extending through the new slits and running
to the old slits which are out of the field in
the upper right. The spider was still sensitive to
vibration at this stage.
138
CHARLES WALCOTT
and the high frequency receptors less. If,
instead of moving the leg, the tension on
the slits was altered with a small glass
probe, it was found that increasing the
tension, i.e., stretching the slits, increased
the sensitivity of the low frequency receptors. Artificially increasing the blood pressure inside the leg had the same effect.
Thus, it appeared that the physical tension
on the leg tunes the sense organ. To explore this further, and also to see whether
the tuning of the receptors was due to a
physical difficulty in getting the leg tip to
vibrate at some frequencies, or whether
once the leg tip was vibrating some frequencies were more effective than others in
eliciting action potentials from the recep0.5
O.I
0.2
0.4
tors, we forced the leg tip to vibrate by
FREQUENCY (kcs.)
cementing it to a crystal phonograph carFIG. 4. The response oE two receptor units to varitridge. By applying a known voltage to the
ous frequencies of air-borne sound. The curve
previously
calibrated crystal we could disrepresents the sound pressure necessary to elicit a
place the leg tip through a known excurthreshold response from a single receptor as indicated by the height of its action potentials. In
sion at any given frequency. Examining
neither case was the leg arranged for maximum
the output of a single receptor unit when
sensitivity at these frequencies.
excited this way reveals that its tuning has
each of the ten receptor units of which the disappeared (Fig. 5). Furthermore, the
sense organ is composed is sharply tuned total output of the ten receptor units of
to a specific frequency which is different which the sense organ is composed is subfor each receptor. In examining the fre- stantially identical to that from a single
quencies to which the different receptors receptor. These results imply that the
on each of the spider's eight legs are tuned, tuning is due to a mechancial resonance of
about 80 in all, we have never found two the leg tip and not to any selectivity in
tuned to exactly the same frequency. Yet the transducing mechanism in the recepthe frequencies of maximum sensitivity for tors.
This finding raises an obvious and cruall the receptors measured lie between 60
and 1400 cps, with the greatest concentra- cial issue: a spider on its web has its leg
tips firmly attached to strands of silk.
tion between 80 and 800 cps.
In measuring the intensity of sound From a physical point of view this is a
necessary to achieve a threshold response situation which much more closely resemfrom the various receptors in a leg, one bles the excitation by the crystal than by
• notices that their sensitivity varies greatly. having the leg tip freely exposed to airIn some legs the unit responding to 80 cps borne sound. To examine this point a spiwill be the most sensitive, the unit at 800 der leg was arranged as before, but the leg
cps the least; in other legs the reverse will tip was attached to a strand of spider silk.
be true. Further investigation disclosed Exciting the other end of the silk strand
that changing the position of the leg with a vibrator revealed no tuning of the
changed the sensitivity of each of the re- receptor units; the response was identical
ceptors; when the leg was flexed the high to that found when the leg was attached
frequency receptors were the most sensi- directly to the vibrator without the intertive; when it was extended, the low fre- vening web strand. But what about the
quency receptors became more sensitive response to air-borne sound? Offhand one
139
VIBRATION RECEPTOR OF SPIDER
10.0
1.0
FREQUENCY
(kcs.)
FIG. 5. The response of a single receptor unit
(dashed line) to direct vibration of the leg tip
with a crystal vibrator. The voltage applied to the
crystal is a measure of its physical excursion at
each frequency. The solid curve is the threshold of
the entire sense organ, all ten receptors taken together, to direct vibration. Threshold is defined as
the amplitude of vibration necessary to elicit a
noticeable change in the rate of action potentials.
would expect the response to be the same
as to web vibration. But doing the experiment showed that the tuning was present!
Furthermore, the sharpness of the tuning
peaks was somewhat greater than before.
Removing the leg tip from the web strand
showed that it responded in a normal
manner to air-borne sound; reattaching it
to the web increased the sensitivity of the
receptor but did not alter the frequency to
which it was tuned. But changing the tension between web and leg had the predicted effect—namely, increasing the tightness
of coupling increased the sensitivity at
lower frequencies, and decreased it at
higher (Fig. 6). At a frequency of 470 cps,
about in the middle of the spider's tuning
range, the change was -[-1(5 db as the tension was increased. The change was greater
(-)-40db) at 103 cps. It appears then, that
with the leg attached to the web a spider
should be able to discriminate frequencies
of air-borne sound but not frequencies of
vibration transmitted by way of its web.
Let us review briefly the information
that a spider might be able to derive from
its 80 metatarsal lyriform organs. The frequency of an incoming air-borne sound
should be coded by whichever receptor
units are active. At frequencies above 1.5
kc, all the receptors seem equally sensitive, and discrimination disappears. Frequency discrimination will also be poor,
even in the low range, for sounds of
relatively great intensity. For example, the
receptor tuned, to a frequency of 102 cps
will be the only one to respond as long as
the intensity is below about -J-80 db. As the
CHARI.ES WALCOTT
140
1
i
i
i
i i
90 -
-
80
-o
UJ
r 70 _
_
CO
CO
jj
tr
a.
60
sour
a
50 -
-
40 -
-
i
100
1
300
i
i
500
i
i i
1,000
FREQUENCY (cps.)
FIG. 6. Increasing the tension between the spider
leg tip and the web strand (lower curve) has
increased the sensitivity of the receptor, but has
not altered the frequency of air-borne sound to
which it is tuned.
sound pressure increases, other units tuned
to adjacent frequencies will begin to fire,
until at about 100 db almost all the receptors will be active but at quite different
rates. Expressed another way, an individual receptor unit has a dynamic range,
i.e., the frequency of action potentials increases with increasing sound pressure,
only over a range of intensities of about
20-30 db. As one receptor saturates by producing its maximum output, other units
tuned to different frequencies begin to respond. This effectively increases the dynamic range of the whole sense organ, but at
the expense of accurate information about
the frequency of the sound. It is also clear
that by adjusting the tension of the receptor slits the spider can greatly alter their
sensitivity. This change with leg position
can amount to as much as 40db. The net
result of all these variables is uncertainty
for the spider about the exact frequency
and intensity of a sound unless it adopts a
strategy for sorting them out. One tech-
nique a spider might use is alternately to
flex and straighten its legs. As it did this,
the tuning of each of its receptors would be
systematically varied but at one point during the "knee bend" would presumably be
optimal. A spider faced with a sound
which saturated one receptor would move
its leg, thus decreasing the sensitivity of
this receptor. The response of adjacent receptors to the incoming sound would also
decrease and perhaps even drop to 0. But
the receptor tuned to the frequency most
closely corresponding to the sound should
drop out last. By flexing and extending its
legs, the spider should be alternately trading sensitivity for selectivity, first at one
end of its frequency range and then at the
other.
Surprisingly, the information produced
by direct vibration of the spider's web is
much less than may be presumed to accrue
from stimulation of the receptors by airborne sound. Frequency discrimination
does not seem to occur in response to
web vibrations. The rather messy web
that Achaearanea builds raises the question of how well vibration is transmitted
by its strands? Clearly the mode of vibration that involves the least loss is that
which alternately stretches and releases the
fiber; i.e., vibration is parallel to the long
axis of the strand. Measuring the attenuation in this mode gave a figure of 1 db/cm
of web for all frequencies from about
40-2800 cps. Reducing the tension on the
web strand increased the attenuation to
perhaps 1.5 db/cm and stretching the
strand to just short of the breaking point
gave only slightly less than 1 db/cm.
Vibrating the web strand at right angles
to its long axis gave noticeably poorer
transmission, but no quantitative measurements have been made.
The usual Achaearanea web is an irregular meshwork of strands. It begins as a
small web made by a young spider, and by
maturity an average web may measure 20 x
20 x 10 cm. Considering the attenuation
of a single strand as 1 db/cm, a vibration
originating at one edge of the web should
be attenuated by at least 20 db in traver-
141
VIBRATION RECF.PTOR OF SPIDER
sing the web. In reality the attenuation is
much greater because no strand runs free
across the web. One strand may intersect
20-100 other branching strands with a
great attendant loss of transmission. Measurements of vibration transmitted across
intact webs are highly variable. The attenuation was never less than 40 db across a
20 cm web and frequently was as much as
80 or 100 db. In contrast, the attenuation
of an air-borne sound over such distances
would be approximately 40 db. These very
crude measurements suggest that airborne sound might provide a better channel of communication between a trapped
fly and a hungry spider than would vibration of the web. The most critical element
in the system is how effectively the buzzing
fly is coupled to the web. If it was only
loosely snared one would expect air-borne
sound to be the most important stimulus.
If it was firmly attached, vibrations of the
web, caused by the insect's struggles particularly at frequencies well below those that
we have been considering might be the
most important.
BEHAVIOR
What use does Achaearanea make of its
tarsal lyriform organ? To answer this question we first examined both the air-borne
and web-borne components of the vibrations made by honey bees (Apis melifica)
and house flies (Musca domestica) snared
in spider webs. The web-borne components were recorded by a calibrated
phonograph cartridge and the air-borne
component by a calibrated condenser microphone. They were recorded simultaneously on a two-channel tape recorder and
compared both by sound spectrograph and
octave analyzer. Both these measures
showed that the frequency spectrum and
power distribution of both web-borne and
air-borne signals appeared to be identical.
Figure 7 presents the air-borne frequency
spectrum generated by a honey bee and a
housefly that were snared in an Achaearanea web. These sound spectrograms tell
us several important things: (1) the maximum energy of the housefly lies at about
300 cps while that of the honey bee is
We do not have any direct measure- about 1200 cps; (2), the frequency range
ments for transmission in orb-webs, but of both bee and fly is exactly the range in
simple observation shows that the mode of which the spider is able to discriminate
vibration is very different. A fly snared in frequencies of air-borne sound; and (3)
an orb-web clearly sets the whole web into the maximum air-borne sound level genervibration. Furthermore, transmission along ated by a trapped fly or bee is about -(-80
the strands, particularly the radii, is prob- db at 1 cm from the insect which would be
ably much better than in Achaearanea, well above the threshold of an Achaearsince they appear to be made of a heavier anea for air-borne sound even if it were 20
silk. It is unfortunate that direct, quantita- cm away. For Araneus, using the measuretive measurements do not exist, but one ments we have made of its threshold at 400
can speculate that transmission of vibra- cps or the behavioral measurement made
tions through the orb-web is more efficient by Frings (1966), the intensity of air-borne
than through Achaearanea's web. Cou- sound at a distance of 1 cm from either a
pling this with our measurements showing trapped bee or fly would be insufficient to
a very low sensitivity of some orb-web elicit a response from the spider. I suspect
spiders to air-borne sound (Araneus diade- that different species of spiders are using
rnalus never gave an electrical response to different cues to trigger their attack behavair-borne sounds of less than —(—80 db at any ior. For the orb-weavers it appears probafrequency between 40-20,000 cps) sup- ble that web-borne vibration is the imporports the importance of web-borne vibra- tant cue; for Tegenaria, Parry (1965) retion in the orb-weavers. This general in- ports that a variety of web-borne signals is
sensitivity to air-borne sound agrees well important. In Achaearanea it is conceivawith the behavioral measurements made ble that air-borne sound plays an important role.
byFrings (1966).
142
CHARI.ES WALCOTT
•01
.1
I
" 10
FREQUENCY (kc)
TIG. 7. The frequency distributions o£ sound energy generated by honey bees and house flies snared
in spider webs. Notice that the main energy peak
of the bee is above 1,000 cps whereas the main
peak of the fly is below it.
FREQUENCY
To explore this question further, we arranged a small loudspeaker in a funnel so
that the sound energy was concentrated at
the small end. Spiders living in normal
webs were exposed to various sounds generated both by audio oscillators and tape
recordings of flies in spider webs. It was
impossible to control accurately the intensity of the sound impinging on the spider
because the windows and walls near the
webs caused a variety of reflections and
(kc.)
standing waves. The sound pressure 1 cm
from the output end of the funnel was
maintained at about -)-60 db. The reactions
of the spiders to sounds presented in this
way were highly variable. Generally, in response to frequencies from 300-700 cps or
to the recording of a buzzing housefly, the
spiders would rush toward the source of
the sound and hold out their front legs
toward it. By moving the loudspeaker
around the web, it was frequently possible
143
VIBRATION RECEPTOR OF SPIDER
to lead the spider from place to place in
the web. The spiders showed no reaction
to air-borne sound of a frequency above
1100 cps nor even to the ultra-sonic pulses
of bats, although electrophysiological measurements showed that spiders could detect
pulses from a flying bat up to 25 feet
away.
These results were then compared with
the effect of vibrating the web directly
with as little accompanying air-borne
sound as possible. Under these conditions,
spiders attacked the vibrator when it was
producing vibrations of 400-700 cps. But at
frequencies above 1000 cps the spiders
either retreated or dropped from their
webs. It is obvious that the animals could
discriminate between vibrations of 500 and
1000 cps. The possibility occurred to us
that the attack behavior seen in response
to vibrations of 300-700 cps and the fleeing
in response to 1100 cps might be related
to the frequencies produced by the bees
and flies snared in spider webs. We tossed
live bees and flies into the webs and found
that although the spiders treated bees and
flies differently, there was no evidence that
their behavior was different before they
actually touched the insect. Such measurements as the time required to initiate an
attack, the time from first orientation
toward the insect to rushing out to it, and
the speed of the approach were all statistically indistinguishable for bees and flies.
Of course, this result does not prove that
spiders cannot distinguish bees from flies.
Nor does it tell us anything about Achaearanea's ability to distinguish frequencies of
sound and vibration. Fortunately, Bays
(1962) reported that he had been able to
condition Araneus diadematus to discriminate between tuning forks vibrating at 262
cps and 523 cps. We were able to repeat
his experiment with Achaearanea, and of
the ten spiders we tried, three were able to
learn to distinguish between the two
tuning forks. How the tuning fork was
presented to the spider was crucially important; if either tuning fork touched a
strand of the web, the spider almost invariably attacked it. The spider only discrimi-
nated between the forks when they were
not touching a web strand. This suggests
that Achaearanea is better able to discriminate frequencies of air-borne sound than
of web-borne vibrations.
To summarize our results, it appears
that Achaearanea has a sensitive vibration
receptor in each of its eight legs. This
receptor appears to be the tarso-metatarsal
lyriform organ; we have never recorded
electrical responses from any other receptor in response to low intensity sound or
web vibration. The physiological properties of this receptor suggest that it might
be used for detecting insects caught in the
spider's web, but behavioral observations
have not shown exactly how the spider
makes use of the information the receptor
should provide. It is quite clear from the
results presented here and from the experiments of others (Parry, 1965; Frings, 1966;
Liesenfeld, 1956, 1961) that different species of spiders use different vibration receptors and different strategies in capturing prey. We know something of the
physiology of Achaearcmeas' receptors; unfortunately comparable information about
the sense organs of the other spiders does
not seem to exist. A comparative study of
prey-capture and vibration-reception in
the various groups of spiders should be
undertaken.
REFERENCES
Frings, H., and M. Frings. 1966. Reactions of orbweaving spiders (Argiopidae) to air-borne
sounds. Ecology 47:578-588.
Gaubert, P. 1892. Rechcrches sur les organes des
sens et sur les systemes Icgiimentaires, glandulaires et musculaires des appendices des Arachnides. Ann. Sci. Nat., Zool., 7th Ser. 13:31-184.
Kaston, B. J. 1935. The slit sense organ of spiders.
J.Morphol. 58:189-209.
Liesenfeld, E. J. 1956. Untersuchungen am Netz
und iiber den Erschiitterungssinn von Zygiella
X-nolata. Zeit. Vergl. Physiol. 38:563-592.
Liesenfeld, E. J. 1961. Ueber Leistung und Sitz des
Erschiitterungssinnes von Netzspinnen. Biol.
Zentr. 80:465-475.
Littauer, R. M., and C. Walcott, 1959. Pulse-height
analyser for neuro-physiological applications.
Rev. Sci. Instrum. 30:1102-1106.
Niclndoo, X. E. 1911. The lyriform organs and
tactile hairs of Araneads. Proc. Acad. Xat. Sci.
Philadelphia 63:375-418.
144
CHARLES WALCOTT
Millot, J. 1949. Classe des Arachnides. I.
Morphologie general et anatomie interne, p.
263-319. In P. P. Grasse, (ed.), Traite de Zoologie, VI. Masson et Cie., Paris.
Parry, D. A. 1965. The signal generated by an
insect in a spider's web. J. Exptl. Biol.
43:185-192.
Pringle, J. W. S. 1955. The function oE the lyriform
organs of arachnids. J. Exptl. Biol. 32:270-278.
Salpeter, M. M., and C. Walcott. 1960. An electron
microscopical study of a vibration receptor in the
spider. Exptl. Neurol. 2:232-250.
Vogel, H. 1923 Uber die Spaltsinnesorgane der
Radnetz-spinner. Jena Z. Xaturw. 59:171-208.
Walcott, C, and W. G. Van der Kloot. 1959. The
physiology of the spider vibration receptor. J.
Exptl. Zool. 141:191-244.
Walcott, C. 1963. The effect o£ the web on vibration sensitivity in the spider, Achaearanea tepidariorum (Koch). J. Exptl. Biol. 40:595-611.
Walcott, C, and M. M. Salpeter. 1966. The effect of
molting upon the vibration receptor of the
spider, Achaearanea tepidariorum. J. Morphol.
119:383-392.