336,

, Reprinted from the .ANNALS

OF THE ENTOMOLOGICAL SOCIETY OF AMERICA. VOL. 76, No. JANUARY 1983

Disturbance Sounds oí Adult Passalid Beetles (Coleoptera: Passalidae):Structural and Functional Aspects1

PEDRO REYES-CASTILLO2 ANO M. JARMAN3

ABSTRACTI

Ann. Entorno]. Soco Arn. 76: 6-22 (1983)Stridulatory apparatus, method of sound.production, and disturbance chirp duration, chirp interval,

chirp intensity, and resonant oscillation have been studied in 17 species of passalid beetles (Coleoptera:Passalidae). These species were, the North American Odontotaenius disjunctus (IlIiger); the MexicanO. zodiacus (Truqui), Heliscus tropicus (Percheron), Oileus rimator (Truqui), Spurius halffteri Reyes-Castillo, Petrejoides orizabae Kuwert, Verres hageni Kaup, Proculejus brevis (Truqui), Pseudacanthusmexicanus (Truqui) , and Passalus (Pertinax) punctatostriatus Percheron; and the African Didimusalvaradoi Corella, D. latifrons Corella, D. nachtigali (Kuwert), Erionomus pilosus Aurivillus, E.planiceps (Eschscholtz), Pentalobus barbartus (F.) and P. savagei (Percheron). Stridulatory apparatusis abdomino-alary, with specialized afeas of abdominal tergum 6 (pars stridens) rubbing against arestricted afea of each metathoracic wing (plectrum). Disturbance sound is due to friction of the ab-dominal pars stridens against the plectrum in the metathoracic wings. Structures thrown into the resonantoscillation by the stridulatory organs are the wings, which bear rows of spines on their underside.

physical aspects of sound produced by the adults. Theseare the contributions of Park (1937), and Alexander etal. (1963) using O. disjunctus, of Baker (1967) usingthree species ofPentalobus, of Miller (1971) using P.barbatus, and of Meyer-Rochow (1971) using A. ed-entulus and P. dilatatus.

Concerning the structure of the sound and the behav-ioral contexts in which the sounds are produced, theoutstanding contributions are two papers by Schusterand Schuster (1971), and Schuster (1975) on soundsproduced by 57 species of New World Passalidae.Schuster recognizes seven structurally distinct sound types,produced in 13 different behavioral contexts. The in-traspecific acoustic repertoire is remarkably "omplex. Inadults of O. disjunctus, 14 different acoustic "signals"have been recognized, associated with II behavioralcontexts, the most known for any arthropod species(Schuster 1975). -

At present, it seems clear that the varied repertoire ofacoustic signals of passalids represents an important meansof intraspecific communication in the complex life his-tories of these species.

The purpose of this work is: first, to clear up theexistent controversy on stridulatory apparatus alreadydescribed by other authors, and second, to verify soundemission mechanism and to analyze qualitative andquantitative aspects of the disturbance sound producedby adults of New and Old World Passalidae species.P.R.C. developed the morphological study, and M.J.was in charge of the measurements and analysis of therecorded sounds. Both authors carried out the experi-ments to detennine the sound production mechanisms.We previously published a paper on larval stridulation(Reyes-Castillo and Jarman 1980) and present hereinstudies of passalid behavior. The species studied were:Didimus alvaradoi Corella, D. latiforn.l' Corella, D.nachtigali (Kuwert), Erionomus pilosus Aurivillus, E.planiceps (Eschscholtz), Heliscus tropicus (Percheron),Odontotaenius disjunctus, O. zodiacus (Truqui), Oileusrimator (Truqui), Passalus (Pertinax) punctatostriatusPercheron, Pentalobus barbatus, P. savagei Percheron,

Stridulation appears to be a universal character of lar-vae and adults of the family Passalidae (Reyes-Castilloand Jarman 1980).

Stridulatory apparatus of the adults has previously beendescribed in Odontotaenius disjunctus (llliger) by Babb(1901), in Pentalobus barbatus{F.) and Proculus goryi(Melly) by Schulze (1912), in Cylindrocaulus patalis(Lewis) by Mizuta (1959), in three species of Pentalo-bus by Baker (1967), and in Aulacocyclus edentulus(MacLeay) and Pharochilus dilatatus (Dalman) by Meyer-Rochow (1971).

By the classification and terms proposed by Dumor-tier (1963), the stridulatory mechanisms are either ab-domino-elytral or abdomino-alary. In the abdomino-elytralmethod of sound production, the plectrum is providedby a ventral area of the elytron, and the pars stridens isformed either by the pygidium (Riley 1872, Schiodte1874, LeConte 1878, Meyer Rochow 1971) or by cer-tain abdominal pleura (Ohaus 1900, Baker 1967). Gahan(1900) disagreed with LeConte (1878), but offered noaltemative opinion about site of the organs of stridula-tion! In fue abdomino-alary method of stridulation, dis-covered by Babb (1901), a pars stridens is made up oftwo stridulatory protuberances, situated on each side offue abdominal tergum 6, which scrape against spiny afeason the undersides ofthe metathoracic wings, called plec-tra (Arrow 1904, Sharp 1904, Schulze 1912, Gravely1915, Dudich 1921, Wheeler 1923, Mizuta 1959, Du-mortier 1963, Reyes-Castillo 1970, Miller 1971, Schus-ter 1975). Hammond (1979) shows a scanning electronmicrograph of the abdominal protuberances in Proculusgoryi and makes a number of interesting inferences. Se-guy (1973) has described a peculiar stridulatory organin passalid adults, consisting of striae on the costal edgeof each metathoracic wing which rub on the tergal plateof the extremity of the abdomen. Few papers analyze

'Work developed within the project. ..Biosystematics. Ecology and Biogeog-raphy of Different Groups of Insects... supported by Subsecrelaria de EducaciónSuperior e Investigación Cientifica. SEP. México Received for publication 9 June1981.

llnstituto de Ecología. Apartado Postal 18-845. Mexico 11800. DF. Mexico3Dept. of Zoology. Universily of BriSlol. Bristol.England

6

0013-8746/83/0100-0617$02.00/0@ 1982 Entofuological Society of America

January 1 REYES-CASTILLO ANO JARMAN: DISTURBANCE SOUNOS IN PASSAL

s- allowed tape speeds from 17/" lo 60 in./sec. (4.75 loJ- cm'-') lo be used, and al Ihe highesl tape speed)f recorder had a frequency response from 150 Hz los. kHz (:t 3 dE). Less crilical recordings were made.1

a domestic recorder and moving-coil microphone, SIype TC530,. which has a frequency range from be

)r 100HzIo.\3kHz(:t5dB).

Jf Stridulatory ApparatusJs:

In every species that we have studied, the stridulale apparatus is abdomino-alary, with the specialized a~s of the abdominal tergum 6, called the pars strid.1 rubbing against a restricted afea of each metathorl'

wing, known as the plectrum. OUT observations con:; those of Babb (1901) on O. disjunctus, who was

) first to perform experimental work on the functiolId of the stridulatory apparatus in a passalid species.

~;~

Pars stridens

at On each lateral part of abdominal tergum 6 is a n11- or less oval afea, the pars stridens, which is a little n~s- sclerotized than the remainder and which has a seri.

cuticular spines ordered in almost regular ridgesIlg tended transversely to the long axis of the body.~o pars stridens covers an afea of nearly 0.5 mm2 in1m zodiacus, and the cuticular spines are only a few micIch in size.

Ilg Randomly situated on the.pars stridens are struct:s-' resembling trichoid sensilla, each with a single seta (:er IH, Fig. 2e and f). The afea around each sensil)1- lacks cuticular spines, in other species shorter. Vi

of the interior of the cuticle of the pars stridenshe shown in Fig. 3d-f.he These details are, with slight interspecific differenks similar in all specimens that we have studied, as 1je as in P. goryi, figured by Hammond (1979).as In histological (Methylene blue-stained) section,x- pars stridens shows numerous small spines on the~d ternal surface as excrescences of the cuticle (Fig.

c). Among these are the trichoid sensilla whose bia are surrounded by a ring of cells within the cutic

~e layer and connected with a scolopale. Beneath the

I~~ luJar layer that secretes the cuticle there is a layer al50 fLm wide containing secretory and duct cells. P

as of convoluted ducts are numerous and lead through~d cuticle to the exterior. Large drops are visible inal secretory cells. The layer of secretory ceIls is vis

only under the stridulatory bosses. Functions of the ~b- silla and the substance produced by the presumed gl)4 dular ceIls remain to be determined.

e- Plect

~d On the underside of each metathoracic wing, a 2-r1S long band, situated immediately anterad to the d), articulation and occupying an afea of 0.25 to 0.5 rrth is the plectrum (Fig. 4). In the folded wings, plectra

parallel and appear immediately above the pars stri(~r of the abdominal tergum 6. The stridulatory afea ofis

wing is covered by microscopic spines a few micror

Petrejoides orizabae Kuwert; Spurius halffteri ReCastillo, Verres hageni Kaup, Proculejus brevis ('qui), and Pseudacanthus mexicanus (Truqui). Adultlast two species have reduced wings, especially P. br.

-Materials and Methods

Beetles were collected in rotting logs in temperattropical forests of the Ivory Coast, México, and the UnStates. Heliscus tropicus was collected in the autum

l' 1970 near Landa de Matamoros, Querétaro, Méxand in 1979 at Tlanchinol, Hidalgo, México. O.junctus was collected in the spring of 1971 in DForest, Ga. In th~ summer of 1977, four other spewere-collected in México: O. zodiacus in AcaxochitPuebla, Petrejoides orizabae in Xicótepec de JuáPuebla, Verres hageni and Passalus (Pertinax) puntostriatus in the Lacandona regían (Lacanjá-Chansa)Chiapas). In 1979, Oileus rimator, Spurius halffteri,Proculejus brevls were talen from Huauchinango, Puland Psuedacanthus mexicanus at Temascaltepec, Mico, In 1980, the Old World species were collectelTai, Ivory Coast. Taxonomy of the New World Pasidae is based on the revision of Passalidae by Re]Castillo (1970)'.

Insects were kept in large plastic tanks contairrotting wood, mostly oak, at room temperature (1:22°C). Water was added from time to time to mairuhigh humidity in the tanks. About 50 specimens of eOdontotaenius species were available, thus permitlsacrificial experiments. Measurements on sound plSUTe levels were made as soon as possible, and 01experiments were completed within 6 months of (lecting the beetles.

Some critical sound recordings were made withbeetle in an acoustically lined box, but most were inopen laboratory. Individuals were distinguished by m,scratched on the pronotum. No distinction was mbetween male and female specimens. CO2 was usedan anaesthetic to facilitate handling the beetles inperiments where the terga were marked with cologrease or parts of wings or elytra were cut.

Scanning electron micrographs were made witlCambridge Stereoscan S4 instrument, with the surfof the animal viewéd at an angle of 45°. Measurememade from left to right of the micrograph are "tru<based on the magnification ser on the instrument, whermeasurements talen from top to bottom of the print ruto be divided by cos 45° as well as by the nomimagnification to give the true size of the object.

Sound intensities were measured with a B & K Loratories, Ltd., sound pressure level meter type 2:(fitted where necessary with the Octave filter ser t~1613). The accuracy of Ibis is within the limits for rcision sound pressure level meters ser by the intertional standard lEC 179. This sound level meter, fitwith the I-in. (ca. 2.54-cm) microphone type 4145, Ia frequency response from 2 Hz to 18 kHz (:t 2 diand it was often convenient to use the instrument as !)microphone and preamplifier.

Output from the amplifier of the sound level mewas red to an Ampex tape recorder type FR 1100. T

ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMEI Vol. 76, IJ

~

FIG. 1.-Pars stridens of tour species of passalid, showing cuticular spinesarranged in rows and setae of trichoid sens(a) H. tropicus; (b) O. disjunctus; (c) and (d) O. zodiacus; (e) and (f) P. brevis.

January 1 REYES-CASTILLO ANO JARMAN: DISTURBANCE SOUNOS IN PASSALI

~

FIG. 2.-Pars stridens of Passalus (Pertina.x) punctatostriatus. (a and b) Latero-posterior border; (c) and (d) cuticular sparranged in rows, central part of stridulatory boss; (e) and (f) cuticular spines and seta of a trichoid sensillum, central proboss.

ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 76, no. 110

FIG. 3.-(a-c) Histological sections through a pars stridens of O. disjunctus, stained in methylene blue; (d-f) Scanning electronmicrographs of the interior of the cuticle of a stridulatory boss of O. zodiacus, ventral view. a, Axon; cc, collar cell; d, duct; s,seta; sp, cuticular spines.

11REYES-CASTILLO ANO JARMAN: DISTURBANCE SOUNOSIN PASSALIDAEJanuary 1983

FIG 4.-Plectrum, showing caudad-directed spines on the stridulatory afea of the wing arranged in rows. (a) and (b) O.disjunctus, (c-f) O. zodiacus.

12 Vol. 76, no. IANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA

FIG 5.-Structures involved in the fixture of the apex of the wing to the interior of the elytron in O. zodiacus. (a-c) wingspines which insert between the lancets of the elytral groove; (d-f) lancets of the elytral groove.

~

January 1 REYES-CASTILLO ANO JARMAN: DISTURBANCE SOUNDS IN PASSAL

size, separated (in O. disjunctus) by a distance of 6 fThe stridulatory afea of each wing measures about (to 0.5 mm2 and contains 5,700 to 11,400 spinesranged in perhaps 660 irregular rows.

Spines, or microtrichia, cover nearly the wholederside of the metathoracic wing, although their sizedensity are notably greater ayer the stridulatory;where they point in a posterad direction in the fa]wing. In general terrns, these spines help in holdingfolding the metathoracic wings under the elytra. TIwings are pulled by specialized afeas of the pleurathe last abdominal terga as well as by special afeathe internal parts of theelytra. Claridge (1968) has omented on this arrangement in some Curculionidae.

It seems that the folding mechanism of the metatlacic wings of passalids is more complex than thaother scarabaeoids, as Herrnann and Anderson (15have stated. These authors reported a total of 19 foldin the metathoracic wings of O. disjunctus. The f,two longitudinal and one transverse, at the level ofdistal articulation are the most important, but the micfolds (at the level of the stridulatory area) are thedeveloped. In macropterous species treated in this pi(i.e., all except P. brevis and P. mexicanus), we rua broadly similar pattern of wing folding.

We think that the complexity of foldings of wingpassalids is caused by the need to keep the stridulaafea free for friction by the stridulatory boss afilieguro 6, which leads to sound production.

A mechanism fixes the folded wings to the undersof the elytra, preventing up-and-down movement ofwing at the distal articulation level during soundduction (Fig. 5a-f). Hammond (1979) has describedgross structure of this arrangement. In each elytron tiis a small distal groove, covered on both sides by sspines in the shape of lancets. On the metathoracic vare numerous spines at the distal articulation level,serted between lancets of the elytral groove. This ti;mechanism, by pressure of the two spiny afeas, usmínimum of energy. Thus, the folded wing is positfixed, (but probably not direction-fixed), both at itstathoracic basal insertion and at its distal end in

elytral groove.

,1.

creating a series of chirps. Some specimens regul~5 continued this repetition for more than 40 rather equr- spaced chirps, other specimens performing les s regul

and for shorter periods. Alone among the specin1- considered, P. .~avagei chirped continuously, in theId sence of specific stimulus from the experimenter,:a

petri dish with rotting wood and other beetles of!d same species.Id;e

Movement of the Abdomen

Id The friction mechani¡¡m which produces the sounJf operated by a series of muscular movements of the[\- domen. Abdominal movements can be studied 1

clearly, by eye or by cine-photography, if the rear haf- of, say, the right elytron and wing are cut off. (Fig.in In the first phase of the movement, the last few~) ments of the abdomen rise and al so their terga m~s anterad, like the blades of a tan. Only during thisjs ward-and-forward phase of the movement is sound m:le The second phase, return of the abdomen to its sole

times rather ill-defined resting position, is silentst often takes a little longer than the elevation.er For specimens of O. zodiacus, sound started wi:d

30 m/sec of the start of abdominal movement, as d,mined both from cine-films and from an experiment w

Df angular movement of the abdominal sterna was mry

tored photoelectrically via a mirror of 1 mm2 atta,f- to the sterna.

Vertical movement of the,abdomen appears to bees mainly to the dorsallongitudinal muscles of segmerle to 5, which probably contract in rapid sequence, anuD- to posterior. The ventrallongitudinal muscles of the stle 2 and 3 mar well take part in the movement, as were

the ventrallongitudinal muscles of the plate which fc1ft the sterna 4 to 6, but their utility is limited by the

19 that sterna 4 to 6 appear fused.n- A forward-and-backward movement of tergum 6 ti19 place during sound production in addition to the vel1

Method of Sound ProductionIn passalid beetles, sound emission is due to fric

of the abdominal pars stridens against the plectrunthe metathoracic wings.. Sound thus produced is clified as a disturbance sound, is grating, and can be ]duced when one breathes upon or squeezes a specinwhen it is laid upon its back, and in many other circlstances that could broadly be described as molestat.In laboratory conditions and in the field when be.are disturbed during collection, some make a singleand-down movement of the abdomen, resulting in agle sound (on the upstroke, the downstroke being silof duration typically 0.1 to 0.3 seco This single sois called a phonatone by Walker and Dew (1972)Leroy (1966), although Miller (1971) and Brougl(1963) use the more descriptive word "chirp." Othis sound is repeated at intervals of about 0.5 sec, 1

'~ FIG 6.-View oto. zodiacus with rear part of right el)'d) removed. Solid lines show the abdominal pleurites and ter:I at resto Broken lines show these at the moment when the SIId ends. The drawing was made from a cine~film shot at 64 fr,In per second; short lines show the intermediate positions 01:n margins of the tergites on each frame of the cine-film.15 dotted oval represents the right pars stridens.

14 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 76, no. l

movement. In producing this back-and-forth movement,not only are the dorsal longitudinal muscles used,butalgo a series of transverse and lateral muscles. Musclesof tergum 6 are much stouter than that of the terga l to5, and moreover several of the muscles of tergum 6occupy different positions or are inserted in specialstructures that occur only in this tergum.

Not only the musculature, but algo the form of tergum6 are important in stridulation. In comparison with therest of the terga, the sixth is irregularly sclerotized, isquite curved, and has a longperimeter. Action of themuscles of this tergum, as well as moving it backwardand forward, causes the stridulatory bosses to emergeso that they reach the stridulatory afea of the wing.

In freshly killed and in anaesthetized specimens, theabdominal stema are fully lowered; the abdomen canthen be pushed upward into the elytra and, when re-leased, it retums to its original position. The inferenceis that elasticity of the abdomen tends to keep it in thelowered position unless muscles act to raise ir. Thisstiffness is not necessarily the only antagonist, but it is

one antagonist to the muscles which pull forward tergum6 during sound production.

Extent of vertical movement of the abdomen duringsound production was measured for the following spe-cies: O. zodiacus 0.79:t:0.06 mm (se, 22 specimens);P. punctatostriatus 0019:t: 0.05 mm (se, 4 specimens);V. hageni 0.37:t:0.13 mm (se, 2 specimens).

The upward part of the abdominal movement is notnecessary for sound production. The abdomen can beheld in the elevated position by the experimenter, andthe beetle still produces a series of chirps, with no up-ward or downward abdominal movement. However, ifthe experimenter moves the abdomen up and down byhand (this experiment was performed with anaesthetizedspecimens ofEo pilosus, E. planiceps, O. zodiacus, P.punctatostriatus, and Vo hageni), all specimens soundon the upstroke. Sound produced is similar to the normaldisturbance sound, but weaker. We suggest therefore,that the wings Test lightly on the pars stridens when thebeetle is not sounding, or that pressure is increased whenthe beetle is stridulating of its own volition.

Extent of the anterad movement of tergum 6 was de-termined from cine-photographs of O o zodiacus. Theforward motion of the pars stridens was 1.4 mm. Weapplied Engineer's Blue (a blue grease) to the pars stri-dens of an anaesthetized specimen; when the beetle re-covered and stridulated a few times, a blue stripe appearedon the wing where the boss has rubbed. In two speci-mens of O. zodiacus, the blue stripes measured 2 mmanteroposteriorlyo This agrees reasonably with the pre-vious figure, when it is remembered that the Engineer'sBlue method will overestimate the afea covered in asingle stridulation if successive movements of the parsstridens do not exactly coincide.

Each chirp included several sound impulses, each ofwhich we attribute to a separate impact of pars stridenson wing spineo Chirps usually end with impulses grad-ually weakened and more widely spaced in time as theforward movement of the boss peters out, but in sub-stantial minority of observations, sound ceases abruptlywithout decrease in amplitude or frequency of impulses.The manner in which the wing is folded shows how thismight occur. Figure 7 gives a simplified viewof thefolded wing. The crosses show the possible travel of thepars stridens along the underside of the wing. It seemslikely that the sounds which termínate abruptly do sowhen the pars stridens has moved forward of point Band lost contact with the folded part of the wing.

We think it significant that the pars stridens rubs ona part of the wing that is strengthened by folds, whichprovide a reasonably firm surface for rubbing. It wouldprobably be inefficient for the pars stridens to rub on

something flabby.Three pieces of evidence suggest that a beetle is ca-

rabie of regulating pressure between wing and pars stri-dens: (1) When chirps are artificially produced by theexperimenter pushing and pulling the abdomen in andout of the elytral space, the resulting sounds are muchquieter than those produced by the beetle's own mus-cular effort. (2) Sometimes, when a series of chirps isgenerated after a single stimulation, the amplitudes of

FIG. 7.-Simplified diagram of view from above right wingof O. zodiacus. The line of crosses from A to B shows wherethe pars stridens rubs.

~

January 1 REYES-CASTILLO AND JARMAN: DISTURBANCE SOUNDS IN PASSAl

)[ that rubs on the plectrum and sets the latter in vibra:e rather than the other way round.

to Analysis of the Sounds

lnterval Between Chirp.\' Linked with the S,15 Disturbance

the impulses in each chirp are a little less than thosthe previous chirp. (3) The beetles are apt to pro(amplitude-modulated sounds, particularly when apently fighting, and these often appear very similadisturbance sounds, except for the modulation.

To vary pressure between wings and pars stri(requires coordination of (a) muscles which depresswing (these might al so include those which depres~elytra and so press down the wing); (b) those whictat every intersegmental joint to cause the posteriorments to curl toward the elytra; and (c) those whichact in tipping and deforming the tergum 6.

The position must be very different in those pass!with reduced wings. Among these are O. nonstri(Dibb) and P. brevis. Schuster (1975) notes that tdisturbance sounds are indeed diffferent from thosspecies with complete wings. Present work with P. b,substantiates this observation.

The Sound Impulse

Each chirp consists of a few hundred events separfrom one another by about l msec. Before each of tievents, a wing spine has engaged on the boss andwing has deformed a little, so storing energy. The SOlproducing event is the release of the wing spine fthe pars stridens, whereupon the wing is free to vitat its own resonant frequencies for a fraction of l mThese few cycles of free oscillation start with a peasound pressure, a "sound impulse." the next engment of wing spine with boss is usually fierce en(to terminate this brief period of free oscillation, leato a short silence before release of this next wing scauses a new burst of oscillation (Fig. 13e).

Arguments are presented below to show that it issanable to regard each sound impulse as being calby impact of a pars stridens on row wing spines, nc

single wing spines.

Terms for the Rubbing Parts

In the adult Passalidae which we have studied, cponent parts of the stridulating organ are the metalacic wings and the pars stridens on abdominal ter:6. The wing is normally fixed, flat, and is the part wloscillations give rise to the sound. The pars stridhowever, is the moving part: it is rounded, and w(not think that it vibrates significantly. Moreover,rubbing afeas on the two parts are markedly unequ¡size; in O. zodiacus, the pars stridens is only 0.4long (anteroposteriorly), and it travels a distance othe arder of 2 mm along the wing during a chirp.

Most authors who have worked on the stridulaapparatus of Passalidae have not concemed themsewith fue question of which part is the plectrum and wthe pars stridens. In arder not to confuse the termsaccord with Dumortier (1963), who reproduces the (sic drawing of 8abb (1901), showing the name ..

stridens" for the stridulatory boss, thus leaving the \1"plectrum" to apply to fue stridulatory afeas ofthe wiWe therefore deliberately choose to accept the sillogicality that, in adult Passalidae, it is the pars stri,

le One disturbance often led to production of a Ict series of chirps, 275 being counted in one expering- on P. punctatostriatu.s. Alexanderet al. (1963) not'IY similar behavior in the scarabaeid Trox .suberosus F.

interval between successive sounds in such seriesis measured at room temperature (normally between

t.S and 22°C; chirp durations and intervals decrease t1r .factor of roughly 1.8 for a 10°C increase in temp)f ture). Intervals were measured from the start ofi.\' chirp to the start of the next. Intervals between ch

in a series were averaged on a reciprocal basis sooccasional very long pauses would not bias the aveldisproportionately. Straight averages would have t

'd about 4% greater than those reported on the recipr,, basis.se Measurements are given in Table l. Spot meas

~~ ments for these and other species can be made fsonagraphs published by Alexanderet al. (1963), B.

~ (1971), Meyer-Rochow (1971), Miller (1971),e Schuster (1975), but these authors did not conduct

c¡ tailed statistical analyses.o Three sources of error contribute to variance in~h

mean value of the internal f<ir any one species: (a:, tervals vary within one series of chirps, (b) serie

19 chirps made by one individual on different occasIg differ from one another, and (c) individual animals d

from one another. We concluded from analysis of ti~~ contributions that averaging 10 intervals per series, 10 series per individual would ensure that, under>n conditions, only variation between individual s w(

contribute significantly to the SE of the mean forspecies. SE quoted in Table 1 are square roots of 1variance (from all sources) divided by number of i

n- viduals of the species measured.Ir- Analysis of variance shows a clear difference bet\lm chirp intervals in the species measure (F=20.1) 01se

species with 82 residual degrees of freedom).s, Not all individual s responded to a single stimulu:lo giving a regular series of chirps. Some respondeclIe giving no more than a single chirp, abolir 300 msec ¡in the start of stimulation (320 msec :!: SE 8.7 msec1m

170 chirps of seven individuals of O. zodiacus). OJn sionally others responded with a series at graduall)

creasing intervals, unsuitable for analysis.

~S Duration 01 Cl

fe Durations of many chirps made by each of sevs- individual s in each species were measured, and resrs are summarized in Table l. As with the chirp intervrd the greatest contribution to SE of the mean was norrn:s.

made by variation between individuals. Again, therht a clear difference between species (F = 70 on 17

liS cies, with 81 residual degrees of freedom).

16 ANNALSOFTHEENTOMOLOGICALSOCIETYOFAMERICA Vol. 76, no. 1

Table 1.-Passalids' species, mass, mean interval between chirps, mean duration of chirps, mean number of impulses per chirp, andsound intensities. Species are arranged in descending order of mass; values in parentheses indicate SE of mean in rows 3 and 4, numberof individuals in row S when different from row l.

2.~21.180.470.450.230150.11

1.991.931.711.601.601.14

0.570.440.300.26

1481 (710 (528 (756 (917 (600 (413 (

706 (719 (626 (386 (974 (550 (428 (429 (511 (552 (

475 (169 (167 (

220 (228 (

176(144 (

198 (176 (170 (82 (

248 (

156(124 (149 (166 (141 (

201 '

113,73,

641

70281

281

7161

3641181115153823212021811152109

54.955.540.525.244.825.243.8

47..240.450.346.343.747.047.133.731.535.9

African1 Erionomus p/aniceps (12)2 Erionomus pi/osus (6)3 Penta/obus barbatus (4)4 Didimus /atifrons (5)5 Didimus a/varadoi (2)6 Penta/obus savagei (3)7 Didimus nachtiga/i (4)

American8 Odontotaenius disjunctus (6)9 Odontotaenius zodiacus (21)

10 Oi/eus rimator (3)11 Procu/ejus brevis (8)12 Verres hageni (2)13 Pseudacanthus mexicanus (4)14 He/iscus tropicus (6)15 Passa/us puntatostriatus (5)16 Petrejoides orizabae (2)17 Spurius ha/ffteri (6)

.SE.bNumber tested.

Chirp duration and interval are correlated (r = 0.96)in the 17 species studied (Fig. 8). This correlation con-tinued when individuals were forced to vary their chirpduration and interval by altering the ambient tempera-tuTeo (Fig. 9).

The most extensively studied species was O. zodi-acus. In one experiment, durations of chirps made byfive specimens were measured on each of 15 oécasions,550 chirps being measured in all. Measurements of chirpduration were subjected to a thorough statistical analy-siso First it was determined that the distribution of these550 durations was not quite normal, there being slightpositive skewness and leptokurtosis. However, distri-bution of square roots of chirp durations was well withinthe acceptable limits in Fisher's quite stringent momentstest for normality (Fisher 1946). Next, the 550 mea-surements were subjected to an analysis of variance,which showed highly significant variation between in-

..

~ 041zo

o-..0.2~~O

Z....

.,,/

FIG. 9.-Graph connecting chirp duration and interval inspecimens of the genus Erionomus, the variation being causedby deliberate changes in environmental temperature. Values areexpressed as fractions of the 20°C values.

./

/"

./

"" dividuals (F = 5.35) and also significant variation, af-fecting all individuals similarly, between occasions (F= 3.28). Similar analyses of variance were made for allspecies studied.

/'/"

v l..MEAN INTERVAL SECONOS

FIG. 8.--Graph connecting mean chirp duration and intervalfor 17 species of passalids. The numbering of the species is inalphabetical order. as listed in Table l.

Sound Impulses

Each chirp, which lasts 100 to 200 msec, is made up,typically, of a few hundred sound impulses. Table I

;:53)";:58):t57):t83):t 136):t35):t33)

:t86):t64):t31):t16):t91):t20):t

13):t32):t37):t57)

:t

11)"

:t5):tll):t29):t24):t30):t9)

:t7):t7):t5):t8):t19):t7)%7):t

10):t7):t19)

(8)"(5)(5)(3)(2)(3)12)15)

:4)

:3)

:1)

January 1983 REYES-CASTILLO ANO JARMAN: DISTURBANCE SOUNOS IN PASSALIDAE 17

likely to have any value from zero to the spacing of theleft-organ impulses, and no greater spacing is possible.Thus, the distribution of spacings in the combined (right-and left-organ) train of impulses will be approximatelya rectangular distribution from O to 200% of the meanvalue as shown (but with the right-hand quarter trun-cated to permit easy comparison with the other diagramson the page) in Figo lObo

Another possible mechanism is that the boss mightstrike occasional wing spines, perhaps particularly longones, randomly positioned on the wingo Here Poissonstatistics would apply and the probability of occurrenceof an impulse spacing of time t would be proportionalto exp( -t/T), where T is a constant provided that theboss moves at constant speed along the wing. The theoryis the same whether one or both organs sound; only Tdiffers. The predicted distribution is shown if Fig. lOcoThe theoretical distribution extends to t = 00, but againhas been truncated for convenience at t = 150% of themean value; the area truncated is 22% of the wholeo

As an example of how these predictions help in de-ciding which possible mechanism of sound productionis actually occurring, one example is taken. This derives

gives number of such impulses in chirps from individ-uals of 17 species. Chirps with large numbers of im-pulses are underrepresented in this table be~ause it isoften impossible to distinguish impulses when they areclosely spaced and those from left and right organs over-lapo Because of bias caused by this, SEs have not beengiven, and the table should be considered as a guideonly, rather than as a list of precise measurements.

During stridulation, the pars stridens move through adistance much greater than their own length. Therefore,number of sound impulses produced in each chirp wouldappear to depend either on number of spines or on num-ber of rows of spines that the pars stridens strike on thewings. In O. zodiacus, bosses wipe an afea of 0.25 to0.5 mm2 on each .wing. This afea contains 5,700 to11,400 spines, arranged in rows which are very evenlyspaced and about 6 IJ.m aparto Thus, each boss encoun-ters about 333 rows in its 2 mm of travel, i.e., about666 rows for the two bosses. Because the number ofimpulses per chirp is a few hundred, it is much morereasonable to regard each impulse as being caused by arow of wing spines than by an individual wing spine.OUT micrographs of the wings of O. disjunctus and P.brevis are very similar to those of O. zodiacus, and itseems reasonable to presume that the regularity of wingspines is a family characteristic in the Passalidae.

Certain other mechanisms can be hypothesized, butthey lead to distributions of intervals between successiveimpulses which are at variance with those observed. Wetherefore need to treat this distribution in detail.

r--1 ~~""l-,..,

~

Distribution 01 Intervals between Consecutive Impulses

To predict the theoretical distribution of intervals be-tween consecutive sound impulses, we assume that thepars stridens travels forward at constant speed, disre-garding first 10% and the last 10% of the impulses.Second, we assume that the regular arrangement of wingspines shown in Fig. 4 is typical of all passalids. Third,we assume that when the right and left organs of a beetlesound simultaneously, impulses created by each are in-dependent of those created by the other.

The easiest prediction results from a hypothetical cir-cumstance with rows of wing spines acting as ridges,each of which causes a sound impulse as the pars stri-dens hits it, and with only one stridulatory organ oper-ating. Here, distribution of time-intervals betweensuccessive impulses would be similar to distribution ofrow spacings on the wing. This would realistically bedescribed by a rather narrow normal distribution. Ois-tribution of row spacings, measured from a scanningelectron micrograph of a wing of P. punctatostriatus,has an SO of 19% of the mean spacing. A normal dis-tribution of this width is shown in Fig. lOa.

Next, we as sume that the same mechanism operates,but that the right and left organs sound simultaneously.Further, we as sume wing spines to be evenly spaced oneach wing and the two wings to be identical in thisrespecto Now, each impulse from, say, the right organfalls between two impulses from the left organ, its sep-aration from the preceding (Ieft-organ) impulse is equally

contagoroadings

~ld

c 50 100 150

Inte.val as percentage of mean

FIG 10.-Distributions of intervals between consecutive im-pulses in a chirp. Intervals are expressed as percentages of theirmean value. Freqeuencies are expressed as the percentage ofintervals whose sizes lie in classes of 5% width, e.g., between75 and 80% of the mean for all intervals. The scales are iden-tical in all four distributions. AIl four distributions have beentruncated at 150% oflhe mean Interval, for convenience. (a,b, and c) Theoretical distributions calculated on three differentassumptions. (d) Measured distribution in a chirp from Pas-sa.ius (Pertinax) punctatostriatus, which is seen to match dis-tribution a better Iban b or c.

~

ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AME! Vol. 76, n

from a chirp made by an individual of the specie5punctatostriatus and containing 178 impulses. The19 and last 8 impulses were neglected as atypical,the remaining 150 spaces were grouped into tenso Espace between impulses was measured and expressela percentage of the mean spacing for its group ofThis manoeuvre corrected for any gradual chang(speed of the pars stridens, as it passed along the wThe resulting distribution, whose SO was :!: 11 % ofmean, is shown in Fig. lOdo It resembles much nclosely the theoretical distribution of Fig. lOa than ttof Fig. 10b or C. Thus, it may be concluded that {one organ could have been sounding during that cland that the most likely mechanism was that ofsound impulse arising from the impact of the parsdens on each row of wing spines, since this is the {mechanism that could yield so narrow a distributiolinter-impulse intervals.

Although regular spacing of the impulses is an all1infallible indication that only a single organ is soundit is less satisfactory to use absence of regular spa<as evidence that both organs are acting simultaneouA different type of argument, again relying on evid(from measurements of impulse spacing, is nextvanced to show that, in another chirp, this timeextraordinarily long one from an individual of the :cies O. disjunctus, both organs were sounding togetl

Figure 11 shows a part clase to the end of an O!logram of the sound from this chirp. Spacing of (impulse from its predecessor is shown on the chartFig. 12. The spacing of each odd-numbered impfrom the previous odd-numbered one is shown on cb, and the same for even-numbered ones in Fig. ]The charts show the classic appearance ofbeats, as wtwo notes of slightly differing pitch are soundedgether, and is just what would be expected if both or!were sounding atconstant, but slightly different imprepetition rates. At about impulse numbers 971, ~1,001, and 1,019, liDes b and c cross, indicatingthe faster generator has changed Tole from contribueven~numbered impulses to providingthe odd-num~ones, or vice versa.

P Wing Re.l'onance

'sr Each sound impulse is followed by a few cycles cld nearly sinusoidal variation of sound pressure, which o;h stops abruptly and is followed by an interval of sileas

before the next impulse, as in the oscillogram of IO. 13a. This is the normal appearance whel) sound impu

of do not follow one another too rapidly. The pictuflg. more confused, as in Fig. 13b, when frequent pu

Ile fromthe two organs overlap. Fig. 13c is a rafe exanre where the sinusoidal oscillation is so prominent that lise else is visible. Similar sounds to that of Fig. 13c car

Iy induced in a beetle that has had one wing cut offrp the opposite elytron raised very slightly so as to freeIle functional wing a little. In Fig. 13d, the oscilloscri- has been used to superimpose traces of the sound pIy SUTe after many impulses, showing the remarkable Iof ularity of form of these sinusoidal oscillations. 1

convenient to characterize the oscillations by a "

1st quency" which is zero-crossings ofthe oscillation.lg, "frequency" was measured for the following spec19 H. tropicus, 9.0 kHz ~ SO 1.0 kHz; O. disjunctus,y.

kHz ~ SO 1.7 kHz; O. zodiacus, 7.8 kHz ~ SOce kHz; P. orizabae, 6.3 kHz ~ SO 0.7 kHz. Ford- species O. zodiacus, where readings were taken fild five individual s on 14 occasions, analysis of variae- showed significant difference between beetles, but n:r.

between occasions. Similar results were obtained iril- experiment with the Erionomus species, even though;h temperature was deliberately.varied from occasiorof occasion between limits of II and 27°C. This suggse

that the resonating structure is one whose mass and s1ft ness are independent of ambient conditions; musclesc.

probably not involved, because their stiffness (~n damping) would probably vary much more than the0- onant frequency appears to do.ns In fact, this concept of "frequency" is rather rse

leading, as Haskkell (1961) points out, because5, measured frequency is influenced by that starting tilar sient, and anyway, several modes of oscillation, eIlg with its own resonant frequency, will be operatin,~d once. The figures are therefore valuable as order~

magnitude, and in comparative experiments, but no m

FIG 11.--Oscillogram of a portion near the end of a chirp from O. disjunctus. used as evidence that both left and right orwere soundin~ simultaneously. Time marker is a l-kHz square wave.

January I REYES-CASTILLO ANO JARMAN: DISTURBANCE SOUNOS IN PASSAL

~~~

vy

.m,"","""",.

FIG. l2.-Charts showing impulse spacing during par! ochirp shown in Fig. 11. (a) Spacing of consecutive impl(b) full line showing spacing of odd-numbered impulse~broken line showing spacing of even-numbered impulses.

A series of experiments was made, on individualfue two Odontotaenius species, to find fue structure wlvibrations determined frequency of fue sound follo\each impulse. First, resonance of the air under the elwas ruled out by replacing fue air by gas mixturewhich the velocity of sound differed greatly fromin air. The frequency produced by fue beetles remaiunchanged, whereas that of a gas column would t.varied in proportion to the velocity of sound in theplacing gas. Mechanical resonances of the elytra othe abdominal sterna were ruled out by applying vition-damping substances to fuese parts, whereuponcillograms of the sound showed the resonances t(undamped and unchanged in frequency. This leaves (wings and abdominal terga as likely resonators. Scing the underside of a wing by a celluloid point crea sound fairly similar (to human ears) to that of analchirp, whereas scraping the pars stridens of a recekilled specimen does noto It is therefore suggestedfue wings contain the resonators which contributesinusoidal sound-pressure variation after each impIJas shown in Fig. l3e.

To localize further the position of the resonatowas necessary to work with specimens from whichwing, and sometimes the elytron on one side, had Iremoved under CO2 anaesthesia. Resonance of themaining wing was unaltered, with its median boclamped to the remaining elytron by forceps withber-covered jaws. Likewise, the distal part of themaining wing, which is folded across the abdomenlies on the opposite side, could be immobilized witlaffecting the resonance. However, sound was drancally reduced by making a slit 4 mrn long in the valongside the costal margin; this slit partially dis(nected the stridulatory afea from the stiff margin oiwing. The experimental evidence thus supports thepothesis that fue costal margin of the wing (which ,tains both the costal and the radial veins)provides

springiness for the resonance. Since the costal mroalso contains most of the mass of the wing, the CGmargin may be the resonating structure. There isevidence concerning mode of vibration, e.g., transvetorsional, etc., nor is there evidence concerning Spelwith reduced wings, such as P. brevis.

To support this assertion, an order of magnitudecalculated for resonant frequency of the costal malof the wing. For this, we measured distributions of nand stiffness along the length of the wing. The l~was determined by clamping the wing, costal maJIhorizontally, and measuring with a Cambridge travel.microscope depression of all points on the marginresulted from hanging a known weight from the diarticulation. Standard engineering methods for calcling resonant frequencies of nonuniform bars yieldedfollowing results for a wing of O. zodiacus: (a) assunfue margin to be position fixed and direction fixec

he the root, but completely free at the distal articulat~s; fue predicted transverse resonant frequency was ca. 1,c) Hz; (b) assuming the margin to be position fixed at

root and at the distal articulation, but direction fixeneither place, 3,900 Hz; and (c) assuming the margi

Df be direction fixed at both root and fold, 8,000 Hz. Tise figures, are of fue right order of magnitude to lend '19 dence to the idea that the costal margin is the frequelra

determining resonator

~~ lntensity of Sounds .

:d Sound intensity measurements were made with..e beetles between 2 and 10 cm from the microphone Ie- sound presssure level meter, sometimes in an aneclof box and sometimes in the open laboratory. No obva- difference was noted between readings in the two sels- When suitable beetles occasionally emitted long seJe of chirps at constant strength, the opportunity was taly to check that the sound intensity appeared to fallp- with increasing distance to the microphone based ones

inverse-square law. This was important, to ensure'al sound intensities were being measured in the far-fly and not in the near-field of the beetle.at All measurements were in dB (A), which is a suitle scale for use in these circumstances; it has already 1:e, established (Schuster 1975), and present studies co

borate, that little energy is radiated by fue adults init ultrasonic region, and the beetles are far too smal

lIe radiate much at low frequencies.~n Table 1 shows average figures for sound intensit:e- fue chirps in each of the 17 species of which we 11er had more than a single specimen to work with. A sb- able average was arbitrarily defined by taking the me- of decibellevels for the five loudest chirps in e,ld measured series from individual s of the species (ut cerned. There is some tendency for larger specie:ti- make louder sounds.19 Measurements were made of sound intensity atn- ious azimuths from one specimen of V. hageni, wlle was at the time making a very long series of chirpy- nearly constant intensity. A slight variation of intelJn- with azimuth (Fig. 14) showed reduced sound emis:i1e rearward and enhanced emission toward each sirle.

ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMEI Vol. 76, n

~

starting transient-, rwing oscillat~r

next sF

/ engage~

n 1~~...rJ'v

disengagemen

I

eFIG. 13.--Osci110grams of sound pressure in parts of chirps. (a) The impulses are widely separated, typical of the period tO\

!he end of a chirp. Time marker 1 kHz. (b) The impulses are so closely spaced as to be hardly distinguishable. Time markkHz. (c) The free oscillation is so great that the starting transient is not visible. Time marker 1kHz. (d) Superposition of consec\impulses, underlining their similarity. Time marker 10 kHz. (e) Suggested explanation of the mechanical events leading tcsound pressures that are recorded oscillographically.

a- quency of the wing also shows in the 8-kHz regio!;h this spectrogram, which was selected to show this po

Sound intensity in each third of an octave was :Iyzed for some specimens of O. disjunctus. One ¡record is shown in Fig. 15. Each vertical columnresents fue greatest intensity achieved in that frequfband at any instant during the chirp. The changingsometimes irregular pulse repetition rate (with itsmonics) dominates fue spectrogram; fue resonant

:~

Evolutionary Asp

r- An abdomino-alary stridulatory apparatus is pre~- in Neotropical, Ethiopic, Oriental, and Australian

~

REYES-CASTILLO AND JARMAN: DISTURBANCE SOUNDS IN PASSALIJanuary I

~I~

~

~

!

~~

'""

Y"

~

~~~~~---~

\

~~

¡

FIG 14.-Polar diagram showinng the variation of S4intensity with azimuth for the chirps from one specimen (

hageni.

~

" 20 25 32 +0 50 '1 80 100 12' l.

Bond "m" '"""nc" kHz

FIG 15.-Diagram showing sound intensity in third-o(bands for a chirp from a specimen of O. disjunctus.

sulted from OUT work appear to US to be: (1) that tl1mechanism of stridulation appears to be abdomino-alaIin species that we have studied; (2) that, at the scanninelectron microscope level of detail, rough parts of tl1stridulatory apparatus are qualitatively similar in all spcies studied, notwithstanding that one, P. brevis, isspecies with much reduced wings; (3) that the stridul.tory afea on abdominal tergum 6 appears to be underla~by a secretory system of gland cells and ducts; (4) tha mechanism fixes the distal articulation of each wilinto grooves in the elytra, previously unrecorded in pasalids; (5) that the terms plectrum and pars stridenapplied to wing and abdomen, respectively, give a falimpression of the modus operandi of these parts; (6) ttsometimes both stridulatory organs sound simultallously in a chirp, whereas at other times only one orgsounds; (7) that interspecific correlation coefficients ttween mass, chirp duration, chirp interval and chirp ;

Ind tensity are positive, but only those between duration aV. interval (r = 0.96; Spearrnan r,'O= 0.93) and betwe

mass and intensity (r = 0.62; r, = 0.61) are significa(8) that structures thrown into resonant oscillationthe stridulatory organs are the wings, which bear roof spines on their undersides. Each time the stridulatlafea on the tergum 6 hits a row of spines, wing oS\latían is stopped. Forward movement of the terguengaged with this row, bows the wing until disengament of tergum from wing allows the latter to twangla few cycles until the next row of spines in engagedthe tergum and the process is repeated.

Among the obvious questions that remain to be20 swered are the following. (1) Is the most impol1

mechanism for conduction of sound from the transrtave ting beetle to the receiving animal (a) through air,

through wood, or (c) through animal-to-animal cont¡(2) How do the beetles create the various other SOUIsuch as amplitude- and frequency-modulated chi

les: clicks, etc., that they are known to produce, usuall:l~nt response to actions by other Passalids? (3) What isp~, nature and purpose of the presumed secretions froms I.n abdominal tergum 6? (4) What mechanisms existlml- sound reception in the Passalidae?the It is clear that much work remains to be done;pe- aspects of sound communication in this interesting f

md, ily of beetles.'-~r

:- AcknowledgmentIy The encouragement and help in many ways of ther- H. E. Hinton and of Gonzalo Halffter are gratefl'r- acknowledged. Academia de la lnvestigacion Cientíre

(Mexico). British Council, Consejo Nacional de Ciely Tecnología (Mexico) , The Royal Society, and UNES.lt. kindly made travel grants to permit the collaborat,

1f- H. Harper, of B. & K. Laboratories Ltd., demonstr:s, the effectiveness of the real time analyzer type 334'rI.g

producing the data for Fig. 15. R. E. Woodruff kil11- supplied the specimens of O. disjunctus, and L. Stl

prepared the slides shown in Fig. 3a-c. The techrhelp of P. Bull, J. Clement, and R. Porter is also glfully acknowledged. We are most indebted to th~

re- viewers for their helpful suggestions.

cies of Passalidae. They represent three phyletic lilAulacocyclinae, Passalini, and Proculini. It is evidthat sound emission in passalids has an ancient ori¡evolving before the separation of Gondwanian landthe Late Cretaceous periodo Notwithstanding the silarities presented by the stridulatory apparatus ofdifferent tribes, the sounds produced are different at!cies levelo Each species has a typical disturbance SOlvery characteristic in chirp duration, number of impulper chirp, and time interval between chirps. This s~ificity of sounds in passalids seems to be biologic:significant as a system of communication. It would 1mit an intraspecific recognition and delimitation ofaging and nidification areas in the decaying logs wl

they dwell.Different species may be found in the same habi

Although sympatry is very common, they occupyferent parts of the same logo Related allopatric specsuch as O. disjunctus and O. Zodiacus, show strilresemblances in their sound characteristics, thus icating possible recent segregation and differentatiol

ConclusionsThe most significant of the conclusions that hay

~

ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AME! Vol. 76, n

The publications cost of this article were paid inby a grant from the Publications Fund of the Univeiof Bristol.

Irt LeConte, J. L. 1878. Stridulation of Coleoptera. Psycl:ty 126.

Leroy, Y. 1966. Signaux acoustiques, comportement ettématique de quelques especes de Gryllides (OrthoptéEnsiferes), Bull. Biol. Fr. Belg. 100; 1-134.3.

Meyer-Rochow, V. B. 1971. Observations on stridul¡e- Australian beetles (Hydrophilidae, Cerambycidae, Pas

dae, Dynastidae) using scanning electron microscopicale- electrophysiological techniques. Forma et Functio 4; :

339.us Miller, P, L. 1971. A note on stridulation in some ceramb

beetles and its possible relation to ventilation. J. Entoe- 45: 63-68.It.

Mizuta, K. 1959. Life off Cylindrocaulus patalis. Ni]Koritgr. K. 4; ]83-234.

a- Ohaus, F. 1900. Berich üder eine entomologische Reise7: Centralbrasilien. Stettiner Entomol. Zeitung 61: 164-1

Park, O. 1937. Studies in nocturna] ecology. Further anaof activity in the beetle Passalus cornutus and descri¡

~, of audio-frequency recording apparatus. J. Anim. Eco11- 239-253.

Reyes-Castillo, P. 1970. Coleoptera, Passalidae: Morfo]11- y división en grandes grupos; géneros americanos. Is. Entomol. Mex. 20-22: 1-240.

Reyes-Castillo, P., and M. Jarman. 1980. Some noteP- larval stridulation in neotropical Passalidae (Coleop>- Lamellicornia). Coleopt. Bull. 34: 263-270.

Riley, C. V. 1872. Annua] report of the noxious bene!LIS and other insects of Missouri: innoxious insects. Mo. :s- Entomol. 4: 139-141.

Schiodte, J. C. 1874. De metamorphos eleutheratorum.s, servationes Bridag til insekternes udviklingshistorie

Hist. Trdsskr. Ser. 3: 9. '

s. Schulze, P. 1912. Die Lautapparate der Passaliden Pralund Pentalobus. Zoo]. Anz. Leipzig 40: 209-216.

Schuster, J. C. 1975. Comparative behavior, acousticalc. Dais, and ecology of the new world Passalidae (Coleopt,

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de Zoologie tome VIII fascicule. 7: 595-702.>y Sharp, D. 1904. The stridulation of Passalidae. Entomol. ~

401: 273-274.ic Walker, T. J., and D. Dew. 1972. Wing movements of~s ing katydids: fiddling finesse. Science 178: 174-176.9:

Wheeler, W. M. 1923. Social life among the insects.court, Brace & World Inc., New York. 375 pp.

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