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Many studies indicate that various vertebrates and invertebrates use sensory cues to recognize predators and to evaluate predation risk. Lizards and birds frequently occupy the same habitats; consequently, avian predation on lizards has been implicated as an important selective pressure on lizard behavior. However, there are few studies on how lizards respond to nonvisual cues. The response of adult male Brown Anoles (Anolis sagrei) to calls of birds was studied to determine whether they use auditory cues as an indicator of predation risk from birds. Anoles responded significantly more often with head tilt (increased vigilance) during playback of predatory vocalizations (Kestrel and Red-tailed Hawk calls) compared with low-risk stimuli (nonpredatory bird calls and white noise). Responses to auditory cues suggest that male Brown Anoles are able to distinguish the calls of birds known to prey upon lizards from the calls of nonpredatory birds. More important, this study demonstrates that anoles, mos...

In most katydids, females listen to and locate a stationary, singing male for mating. Pair formation differs in phaneropterine katydids where pairs form duets and the male typically Þnds the female after hearing her acoustic reply to his song. We recorded the duetting behavior of two cryptic species of phaneropterines, Amblycorypha rotundifolia (Scudder) and Amblycorypha alexanderi Walker (Tettigoniidae: Phaneropterinae), from populations in their zone of sympatry. The songs of the two species differed in their temporal properties, and the duets differed in the timing of the femaleOs replies with respect to the maleOs song. We also measured the hearing sensitivity and auditory tuning in these species by recording extracellular neural responses to sound stimuli varying in frequency and intensity. Individuals of both species were most sensitive to frequencies near 13 kHz, which corresponds to the frequencies of the malesO calling songs and to the peak frequency in the femalesO tick responses. Both species also responded to pulses with ultrasonic carrier frequencies. For higher amplitude stimuli, neural responses had shorter latencies and more action potentials. Latency functions differed for low-frequency and high-frequency stimuli. These data form the basis for understanding how auditory processing and sexual selection might be involved in the recent diver- gence of these two cryptic species.

Since 1934, the rotundifolia complex of Amblycorypha has consisted of two named species: Amblycorypha parvipennis Stal, occurring from the Mississippi River westward into the eastern edges of the Great Plains, and Amblycorypha rotundifolia, occurring in most of the eastern United States. The latter entity is here shown to consist of at least three species with distinctive calling songs and different but overlapping geographical distributions. At 25C, A. rotundifolia (Scudder) produces 26 calling song units (phonatomes) per s, whereas Amblycorypha bartrami n. sp. Walker, A. parvipennis, and Amblycorypha alexanderi n. sp. Walker produce 10, 5, and 2.8 ph/s respectively. Amblycorypha rotundifolia occurs from Illinois to New York and southward along the Appalachians to northern Georgia. Amblycorypha bartrami occurs in the southeastern states, and A. alexanderi broadly overlaps the distributions of the other two eastern species. Where A. alexanderi and A. rotundifolia are sympatric, the two occur in similar habitats; where A. alexanderi and A. bartrami are sympatric, A. bartrami occurs in more xeric habitats. No morphological characters were found that reliably identify the three eastern species, yet no fewer than three species must be recognized to provide names for populations that behave as distinct species where they co-occur.

We have studied auditory responses in two species of mole cricket (Scapteriscus borellii and S. abbreviatus) to determine (1) whether they show sensitivity to ultrasound, (2) whether their hearing (at both low and high frequencies) is based on the same neural circuitry as that of true crickets, and (3) whether ultrasound sensitivity in different mole cricket species varies with their ability to fly. S. borellii are sensitive to ultrasonic frequencies. There is evidence of a segregation of frequency bands in prothoracic auditory neurons. There are two pairs of omega neurons (ONs) with similar morphology to ON1 of true crickets. The two pairs of ONs differ in tuning. One pair has two sensitivity peaks: at the frequency of the calling song of this species (3 kHz), and in the ultrasonic range (25 kHz). The other pair lacks the high-frequency sensitivity and responds exclusively to frequencies in the range of the species song. These two types are not morphologically distinguishable. In S. abbreviatus, only one class of ON was found. S. abbreviatus ONs are narrowly tuned to the frequency of the species’ calls. A T-neuron had the best ultrasonic frequency sensitivity in S. borellii. This cell showed a broad tuning to ultrasonic frequencies and was inhibited by low-frequency stimuli. A morphologically similar neuron was also recorded in S. abbreviatus, but lacked the high-frequency sensitivity peak of that in S. borellii. We also assessed the responses of flying S. borellii to ultrasound using field playbacks to free-flying animals. The attractiveness of broadcast calling song was diminished by the addition of an ultrasound signal, indicating that S. borellii avoid high-frequency sound. The results indicate that mole crickets process low-frequency auditory stimuli using mechanisms similar to those of true crickets. They show a negative behavioural response to high-frequency stimuli, as do true crickets, but the organization of ultrasound-sensitive auditory circuitry in mole crickets differs from that of true crickets.

Previous studies have shown that sexually signaling males across different taxa show stereotyped spacing behavior that may be related to aspects of their signals, such as intensity. However, few studies have shown that the separation between signaling males affects their relative attractiveness. Using two sound traps broadcasting the calling song of the cricketEunemobius carolinus, we show that the separation, relative intensity, and absolute intensity of the calling songs influence calling song attractiveness. For calling songs separated by 5 m, the proportion of individuals attracted to the higher intensity song increased as the relative intensity difference of the two songs increased from 3 to 6 dB. For calling songs that differed by 6 dB, relative attraction to the less intense song decreased with decreasing song separation. These two results are consistent with the predictions of a model (Forrest and Raspet, 1994) that suggests that dense spacing is more costly for less powerful singers and that this cost increases with increasing differences in relative intensity. When the relative intensity of the songs was held constant (6 dB), we found that discrimination between songs decreases as the song absolute intensity increases. In particular, a greater proportion of individuals was attracted to the high-intensity song when the songs were broadcast at 103 and 97 dB than when the songs were broadcast at 109 and 103 dB. Unlike mammals and birds, the ability ofE. carolinus to discriminate between songs that differ in intensity may decrease as the absolute intensity increases. This may mean that females are less discriminating when they are closer to singing males.

We sampled a population of signalingPhoturis versicolor quadrifulgens fireflies to quantify the variation in flash patterns emitted by males. Males produced five distinct flash patterns during their mate-searching flights. Four of the patterns consisted of two to five equal-intensity pulses and the fifth pattern type was a flicker, a group of rapid modulations in intensity. We found that the proportions of each pattern remained relatively constant from night to night throughout the season. The different flash patterns produced varied significantly with time of night; patterns having fewer pulses occurred earlier in the evening. Local density, an estimate of competition, did not significantly correlate with flash pattern type. On consecutive emissions, individuals changed their flash types with a mean probability of 0.12 (over all males), and they usually switched between patterns differing by a single pulse (from a two- to a three-pulse pattern, from a three- to a two-pulse pattern, etc.). The nightly temporal changes in flash patterns may be related to tradeoffs between female availability and energetic costs of signaling or the changes may be related to increased predation risk from visual predators.

Attraction of flying mole crickets to individual males calling in an outdoor arena was influenced significantly by the relative intensity of the males calling in the arena. Louder males attracted more individuals than males whose calling songs were less intense. Making simple assumptions about the acoustic output from calling males and about the flight pattern and response of flying females, the differential attraction can be explained by a mathematical model. Computer simulation of the model was used to examine the importance of a male's intensity relative to others and the effect of distance between males on the attraction of females. The model and its relation to active female choice and passive attraction are discussed. The model makes predictions about differences in spacing behaviour of males that maximize attraction relative to other males.

We describe the paired hearing organ of the scarab beetle Euetheola humilis. The auditory structures of the beetle are typical of other insect ears in that they have a thinned tympanic membrane backed by a tracheal airsac with associated chordotonal sensory structures. The tympanic membranes of the beetle are part of its cervical membrane and are located behind the head, where the cervix attaches dorsally and laterally to the pronotum. Each membrane is approximately 3 μm thick. The chordotonal sensory organ, which lies within the tracheal airsac, contains 3–8 scolopidia that attach by accessory cells directly to the tympanic membrane. Neurophysiological recordings from the neck connective of the beetle revealed that the auditory system is sensitive to frequencies between 20 and 80 kHz and has a minimum threshold of approximately 58 dB at 45 kHz. The neurophysiological audiogram is identical to the behavioral audiogram for a head roll, one behavioral component of the beetle’s startle response elicited by ultrasound. Blocking experiments show that the membranous structures on the cervix are indeed the hearing organs. Neurophysiologically determined thresholds increased by more than 35 dB when drops of water covered the tympanic membranes and were essentially restored to the control level when the water was later removed. At least three other genera of Dynastinae scarabs have similar tympanum-like structures located in their cervical membranes. Behavioral and neurophysiological data show that the frequency tuning of species in two of these genera, Cyclocephala and Dyscinetus, is nearly identical to that of E. humilis. Our discovery represents only the second group of beetles known to respond to airborne sounds. However, the hearing organs of these scarab beetles differ in structure and placement from those of the tiger beetles, and thus they represent an independent evolution of auditory organs in the Coleoptera.

Scotch broom, Cytisus scoparius (L.), a weed in the Pacific Northwest, is rapidly invading open areas and ecologically sensitive dunes along the coast. Scotch broom populations also exist in the eastern United States, but are apparently stable and not expanding. The eastern Scotch broom populations may be kept in check by the broom weevil, Bruchidius villosus (F.), a bruchid found in eastern populations of broom but absent from those in the Northwest (Bottimer 1968). We studied the natural history and biology of the broom weevil in North Carolina. Our purpose was to relate the bruchidis life history to the phenology of the host plant and to quantify oviposition and seed destruction by the bruchids. Adult weevils were active around the plant from the first flowering in early spring until dehiscence of the seedpods in summer. The sex ratio of the beetles was nearly 1:1 throughout the adult activity season. The number of weevil eggs laid on the pods was correlated to the length of the pod and to the number of seeds in the pod. The larvae develop in and destroy the seeds of the broom plant. Seed destruction at two sites in North Carolina was more than 80%; a field experiment showed that seed destruction was dependent on the density of beetles in cages on the plants. Because of its impact on seed production, the broom weevil may be a viable candidate for biological control of broom in the Northwest.

The signals generated by acoustic insects exhibit temporal patterns on several time scales. Annual or seasonal rhythms provide information about temporal changes in insect population size. Knowledge of such changes might be useful in ecological monitoring programs. Circadian or daily rhythms commonly seen in insect signaling are generated by endogenous ‘‘clocks’’ that are reset by environmental cues. Understanding these daily patterns is also important for monitoring insect populations. Within insect populations, the signals of neighbors sometimes show temporal patterns of synchrony or alternation with timing on the order of seconds. The phase relationships among individuals are maintained by acoustic resetting, whereby an individual’s temporal rhythm will change depending on the phase that neighboring signals are received. On still smaller time scales, temporal patterns of insect songs are diverse and generally differ among species. These small‐scale patterns are often essential components of mating signals and are used in mate recognition and mate choice.

Snowy tree crickets produce a rhythmic acoustic signal composed of short chirps. The chirp rhythms are very regular and dependent on temperature. When signaling in groups, males synchronize their chirps. The rhythmic signals of these tree crickets were used as a model of a ‘‘biological oscillator.’’ The phase responses of males to single probe stimuli similar to the male calling song were measured. The phase response curves (PRC) of males showed both strong (type 0) and weak (type 1) resetting. PRCs differed depending on amplitude, duration, and frequency of the resetting stimuli. In other experiments, males could adjust their natural periods by as much as 15% when phase‐locking (1:1) to an entrainment stimulus. Signaling behavior of males was compared with a simple model of coupled oscillators. The phase resetting was not consistent with the simplest resetting model, in which the male’s phase shift is completed after one cycle of the chirp period. In addition, a simple iteration of the PRC could not simulate the phase‐locking observed in the entrainment experiments indicating that the acoustic coupling between males differs from a simple resetting model.

The tonal quality and temporal complexity of bird vocalizations have long suggested that birds may excel in auditory spectral or temporal processing. However, most psychophysical studies support the notion that birds have spectral and temporal resolving power roughly comparable to that measured in humans. Rarely have such psychophysical tasks involved both frequency and time cues. An intriguing aspect of gap‐detection experiments with sinusoidal markers is the robust dependence on the frequency separation between the markers. In humans, silent gaps become more difficult to discriminate as the frequency difference between the markers increases. This frequency‐dependent pattern of thresholds is well fit with a roex‐filter model. Here, budgerigars were trained by operant conditioning to discriminate a change in the duration of a silent gap between two tonal markers. Frequency separation between the tonal markers had only a small effect on gap discrimination thresholds in budgerigars, suggesting an unusually ...

Frequency responses of shallow, freshwater ponds in northern Mississippi were measured. The response has a highpass characteristic with a sharp cutoff frequency due to the modal properties of the system. The cutoff frequency of the system is inversely related to the depth of water at the shallower transducer (projector or receiver). Frequencies below the first mode are nonpropagating, and the overall effect of this environment on propagation is about 50 dB. Several species of aquatic insects communicate in these shallow‐water ponds using acoustic signals, and they must contend with the physical constraints imposed by the system. Data on the calling song (long range) of a common aquatic beetle (Tropisternus collaris, Hydrophilidae) are presented and discussed in relation to the propagation characteristics of their shallow pond habitats. [Work supported by USDA.]

To infer mating preferences of female Neonemobius sp., we monitored their proximity to males paired in laboratory enclosures. Females were found significantly more often near the larger of the males, and more often near a calling male than a silent one. The proportion of time individual males were observed calling was significantly correlated with male size. Females did not prefer virgin to mated males. When allowed to mate, females mated with the larger of the pair 5 of 7 times. Female preference for large males may result from selection on females to obtain larger investments from males. Female nemobiine crickets feed on glandular secretions provided by males during mating. Large males may offer more material, and females may use male calling songs as a cue to male size.

Lifetime oviposition by caged, individual female southern and tawny mole crickets, Scapteriscus acletus Rehn & Hebard and S. vicinus Scudder, was monitored outdoors; oviposition was highly seasonal. Females that matured in the fall did not oviposit until the following spring along with females that matured in the spring. Most eggs were laid in May and June and percent hatch of clutches decreased later in the season. Dry weight of eggs, number of eggs per clutch, and percent hatch decreased with successive clutches from individual females. Average investment in eggs per clutch ranged from 10 to 24% of female body weight for S. acletus and from 5 to 16% for S. vicinus females. Lifetime investment was >100% of female body weight for 6 of 12 S. acletus females, but only 1 of 8 S. vicinus females had a lifetime investment in eggs equaling its body weight. In S. acletus, but not S. vicinus, large females produced more offspring and average size of their egg clutches was larger than those of smaller females.

Insect size tactics or developmental strategies are discussed in relation to decisions individuals make about when to mature. Such decisions carry with them costs and benefits in terms of that individual's reproductive success. Whenever size affects fitness, selection should act such that individuals evaluate the costs and benefits due to changes in size and should mature when the ratio of benefit to cost is maximized.Predictions about seasonal changes in adult sizes within a population are tested on two species of mole cricket, Scapteriscus acletus and vicinus. Specifically, individuals maturing in the fall should be larger than average because there is no cost associated with delayed reproduction since reproduction occurs only during spring months. Smaller than average individuals should remain in juvenile stages and get larger before reproducing. Also it is predicted that as the spring reproductive season progresses a greater proportion of smaller individuals should mature because the costs due to delaying reproduction increase. The changes in seasonal distribution of adult sizes of mole crickets support the predictions and suggest that individuals make decisions about when to mature based on costs and benefits associated with changes in size.

The southern mole cricket, Scapteriscus acletus, is known throughout the Southeast as an important agricultural and turfgrass pest. Several decades of research on these insects have not yielded satisfactory control methods, perhaps because little has been learned of their basic biology and reproductive behavior. This lack of knowledge stems from the fact that mole crickets are burrowing crickets, spending most of their lives underground. Male and female external morphologies are identical except for the forewings. Male S. ac7ctus, as in many cricket species, produce sound to attract sexually responsive females (Alexander 1975). The sound producing apparatus is manifest as a black spot on the male's forewing; it consists of a scraper and a stridulatory file on each forewing. Sound is produced during stridulation when the scraper of one wing rubs the file of the other wing. Although this apparatus is typical of acoustical crickets, mole crickets are unique in their acoustical behavior. Males call from within special burrows they construct each night prior to calling. Using their fossorial forelegs and large pronotum, males pack and shape the opening of their burrow into an exponentially expanded horn. Bennet-Clark (1970) has shown that this shape amplifies male calling songs in 2 European mole crickets, Gryllotalpa gryllotalpa and G. vineae. This amplification probably holds true for S. acletus (Nickerson, Snyder, and Oliver 1979). Male S. acletus produce a continuous trill during the calling period. This song is species-specific with a carrier frequency of about 2.7 kHz modulated at 50 pulses per second (Ulagaraj 1976). I placed individual S. acletus males in soil-filled, 19-liter buckets. These buckets were covered with aluminum screen to prevent the male escaping, placed in a pit, and surrounded by a trapping device (Fig. 1). Males could then be observed for calling behavior and responding animals trapped around the buckets. A modification was made to assess flight from buckets: the aluminum screen cover was removed and the entire trap covered with a cylindrical hardware cloth cage. Individuals flying from buckets hit the cage, fell, and were trapped around the buckets. Twelve S. acletus males were monitored for nightly calling period with respect to sunset (Fig. 2a). Individual males differed significantly in their

Male crickets produce calling songs that function to attract mates. Sound is produced when membranes of the wings are caused to vibrate during stridulation. Sound fields were measured for three species of crickets. Two species of mole crickets, Scapteriscus acletus and s. vicinus, call from within burrows constructed in the soil. Sound fields of the mole crickets were hemispherical and the power output averaged 4 μW (N = 22, range 2–22 μW). Power output was dependent upon male size and moisture content of soil surrounding the burrow. Efficiency of sound production was estimated to be less than 0.2%. Sound fields of a species of tree crickets, Oecanthus quadripunctatus, approximated that of a doublet source. Power output ranged from 2–17 μW (N = 6) and efficiency was estimated at about 1%.

Accurate estimates of population size are needed to understand the population dynamics of any species. They are also needed to determine when to implement a specific control tactic, and to measure whether that control tactic has been effective. This paper discusses the use of acoustic signals produced by insects and the feasibility of using these signals to census populations. Insect sounds are either incidental (produced as a by-product of some activity) or non-incidental (produced to cause a response in some other animal). Incidental sounds differ from non-incidental sounds with respect to several features that are important to using sound to census populations. These features include species specificity, frequency content, ease of localization, distance traveled, and the duration and timing of sound production. Studies of crickets show that information about which individuals in a population are producing sound, when the individuals produce sound (seasonally and daily), and the probability that individuals produce sound during census periods must be known to accurately estimate the size of a population.

Wing folding in the Insecta evolved early in the history of the group and often the wings are folded one on top of the other over the abdomen. Whether or not the right wing is folded over the left or vice versa is of little importance except when the two wings have evolved different tasks. Such is the case in a number of families of Orthoptera: Gryllidae, Gryllotalpidae, Haglidae, and Tettigoniidae. In these families the forewings of the males are specialized for sound production. The plectrum, or scraper, of one wing is drawn across the pars stridens, or file, on the underside of the other wing. This action causes certain membranes of the wing to vibrate and produce sound. Usually the right wing rests over the left in crickets and the left rests over the right in katydids. Interestingly, the females, whose wings are not usually adapted to produce sound, follow the same rules (Masaki et al. 1987). In many species, because of the specialization of the two wings, they differ considerably with respect to pigmentation, reduction in the number of teeth on the file, and in retrogression of the file (Masaki et al. 1987). In the haglids the males may sing using the left over the right or the right over the left (Morris & Gwynne 1978) and apparently can switch while singing (Spooner 1973). I have examined the wingedness of both sexes in two species of mole cricket, Scapteriscus acletus and S. vicinus, to determine how they relate to the other three groups. Individuals were collected as part of another study (Forrest 1986 ) from the routine sound-trapping station on the Agronomy Farm of the University of Florida (Walker et al. 1983). Quarter-monthly samples of up to 50 individuals were collected during the crickets' spring and fall flights of 1981 and 1982. A total of 1431 S. acletus females, 1222 S. acletus males, 714 S. vicinus females, and 284 S. vicinus males were captured and classified as to wing overlap. These are the largest samples of singing Orthoptera where the wingedness of individuals has been studied. In neither sex of either species did rightand left-wingedness differ from 50:50. Female acletus were 51% right-winged (734:697), males were 49% right-winged (602:620). For vicinus, females were 51% right-winged (367:347) and males were 48% right-winged (135:149). I also examined 19 (2 males and 17 females) Neocurtilla hexadactyla, the northern mole cricket, from the Florida State Collection of Arthropods. Both males had right wings over left but only 5 of the 17 females were this way. Checking two other species of mole cricket, Scapteriscus abbreviatus [n= 13; males (4:4), females (1:4)] and Gryllotalpa africana (n=4), revealed at least some specimens with each configuration. Masaki et al. (1987) found equal numbers of left-winged and right-winged males of a scaly cricket, Ornebius kanetataki. I examined 30 male Cycloptilum antillarTium, another mogoplistine, from the collection and found 16 (53%) with their right wing over their left. It is interesting that the mole crickets and scaly crickets would differ so greatly from the other gryllids and tettigoniids with respect to the constancy of wing overlap. One possible reason for the differences might be because of the ancestry of the group. Evidence from the fossil record leaves "no doubt that mole crickets developed from