Thomas J. Walker

Acoustic Synchrony: Two Mechanisms in the Snowy Tree Cricket

Snowy tree crickets synchronize their chirps by responding to the preceding chirp of their neighbors. If a neighbors chirp precedes his own, a cricket shortens his chirp and the following interval. If it follows his own, he lengthens his chirp interval and sometimes the following chirp. A single response of the first type may advance his phase of chirping 160� and one of the second type may retard it 200�.

Energetics of Singing in Crickets: Effect of Temperature in Three Trilling Species (Orthoptera: Gryllidae)

Summary1.Oxygen consumptions of resting and trilling crickets were measured at various temperatures. Oscillograms taken at comparable temperatures were used to identify the major factors determining the cost of stridulation.2.Species used wereAnurogryllus arboreus (mass ≃0.4 g), wing stroke rate at 23°C of 71 strokes per s; andOecanthus celerinictus andO. quadripunctatus, two sibling species, (masses ≃0.06 g), wing stroke rates at 23°C of 57 and 38 strokes per s respectively.3.At 23°C the three species have similar total mass-specific metabolism during singing (

Effects of temperature on rates in poikilotherm nervous systems: Evidence from the calling songs of meadow katydids (Orthoptera: Tettigoniidae:Orchelimum) and reanalysis of published data

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Cryptic Species Among Sound-Producing Ensiferan Orthoptera (Gryllidae and Tettigoniidae)

μl·(g·h)−1; Table 3) even though their wing stroke rates are different.4.A. arboreus has no change in net singing metabolism with increasingTa; however, cost per wing stroke decreases slightly. TheOecanthus both increase their net singing costs with increasedTa and the cost per wing stroke remains roughly constant.O. quadripunctatus has a cost per wing stroke about 1.6 timesO. celerinictus (Tables 1, 3; Fig. 10).A. arboreus does not elevate its thoracic temperature significantly while stridulating and it is doubtful that tree crickets thermoregulate due to their small size.5.The cost of singing inA. arboreus varies from 10 to 16 times resting; inOecanthus, from 6 to 12 times resting (Table 3).6.Although the two tree cricket species have different wing stroke rates at any common temperature, the number of file teeth struck per s is almost the same;A. arboreus strikes nearly twice as many teeth per s as do either of the tree crickets (Fig. 9).7.The two factors that explain most of the variation in net cost of trilling are the wing stroke rate (Fig. 10) and the number of teeth struck·(wing stroke)−1. Related factors that merit study are interspecific differences in file tooth depth and angle, wing mass, and wing velocity.8.For three species of crickets and two species of katydids the average net cost of trilling is about 1.5×10−5 ml O2·(g·wing stroke)−1 (Fig. 10).9.Chirping should be energetically less expensive than trilling, with costs equivalent to the average cost per wing stroke times the total number of wing strokes per time. The latter factor is 10–95% lower in chirping species than in trillers.10.An estimated daily respiratory energy budget shows calling taking about 56% of the daily respiratory budget ofO. celerinictus and 26% forA. arboreus (Table 4).

Monitoring the Flights of Field Crickets (Gryllus Spp.) and a Tachinid Fly (Euphasiopteryx Ochracea) in North Florida

A knowledge of the intraspecific variation in cricket calling songs1 and of the factors causing these variations is fundamental to the study of other aspects of the songs. For instance, work on the behavioral significance of the calling song must take into account the changes in calling song that occur with changes in certain environmental factors. Likewise, evaluation of interspecific differences and attempts to explain their origin are dependent upon a correct understanding of intraspecific differences. Finally, one working on the nervous control of singing must know what he has to explain before he can produce a thorough explanation. The factors responsible for intraspecific variation in cricket calling songs can be classified conveniently under three headings: (1) current environment, i.e., the environment of the cricket at the time he is producing the song, (2) previous interactions with the environment, and (3) genetic factors. Each of these will be discussed in turn, but first I will describe the mechanism of sound production in crickets and the physical characteristics of cricket calling songs.

Symposium: Insect Behavioral Ecology--85: Stochastic Polyphenism: Coping with Uncertainty

Summary1.Male calling songs of 10 species ofOrchelimum were tape-recorded 9 to 52 times over ranges of ambient temperatures as great as 20 °C.2.For each species the relation between wingstroke rate and temperature was approximately linear. Calculated regression lines had coefficients of determination (r2) between 0.76 and 0.99 (aver.r2=0.93). The slopes of the regression lines varied from 0.9 to 5.1, but when extrapolated downward toŷ=0, the lines tended to converge at 11 °C (x±SD=10.9±1.9).3.These results are similar to those published for 27 species of crickets and known for 20 additional species of katydids.4.In previous studies, by others, the effects of temperature on rates within poikilotherm nervous systems have generally been reported asQ10 values. Such values are appropriate if rates approximate an exponential function of temperature. However, reanalysis of 15 published data sets that were adequate to justify a comparison showed that 13 fit a linear model more closely than an exponential one. Furthermore, if one half a data set was used to predict the other half, the linear model was superior to the exponential model 26 of 30 times. The temperature ranges of the 15 data sets were as small as 12 and great as 26 Celsius degrees.5.For those 13 data sets with anr2>0.90, the regression lines tended to converge like those of katydids and crickets. For seven species of electric fish the values ofx whenŷ (discharge rate)=0 clustered about 4 °C (x±SD=4.0±1.8 C).6.Empirically the linear model is superior to the exponential one in (1) goodness of fit, (2) prediction of effects beyond the temperature range studied, and (3) prediction of data sets from a single or no datum.7.The origin and slope of the linear regression are generally more useful thanQ10 values as short-hand expressions of temperature effects on rates in poikilotherm nervous systems.8.Rates in poikilotherm nervous systems are more complex in their determinants than are rates ofin vitro chemical reactions. It is therefore not surprising that the former rates fail to show the simple exponential relations to temperature that the latter show. On the other hand, that poikilotherm nervous systems should generally have approximately linear relations to temperature and that the extrapolations of linear regression lines should tend to converge at zero rate are unexpected and reveal a need for more study of underlying causes.

Pulse Rates in the Songs of Trilling Field Crickets (Orthoptera: Gryllidae: Gryllus)

The life cycles of crickets can be divided into two basic categories, one with seasonality and the other without it (Alexander, 1968). Since adult crickets live a relatively long time and continue to lay eggs, this distinction may become vague in warm climates. Even in such cases, however, the two categories can be recognized when the underlying developmental characteristics are experimentally analyzed. A life cycle that shows a more or less fixed phase relationship with the seasonal cycle of environment usually involves physiological responses that buffer the life cycle from perturbing fluctuations in external conditions. Such responses form a coordinated system of seasonal homeostasis, in which diapause and photoperiodism are principal components. When development is controlled by this system, its rate is not always a simple function of temperature. The thermal coefficient Q10 is often shifted from an ordinary value of 2–3 to a lower or even a negative one by intervention of diapause or other photoperiodic responses. The life cycle thus includes thermally heterogeneous phases. This situation may be described by the classical though not widely used word heterodynamic (Roubaud, 1922). When there is no such switching of developmental phases, the cricket responds to heat summation in more or less similar ways throughout the entire life cycle, so that its development is homodynamic These words are used here because of their convenience and adequacy.

Arboreal singing in a burrowing cricket,Anurogryllus arboreus

Studies of calling songs and seasonal life histories of crickets and long-horned grasshoppers have revealed many species that were unrecognized on the basis of morphological studies. Once recognized, such cryptic species usually prove to have identifying morphological characters. Nearly one-fourth of the ensiferan species of eastern United States are cryptic, and high proportions of cryptic species have been found in other groups that have conspicuous, non-morphological, species recognition signals or that have been intensively studied. Similarly high proportions of cryptic species must exist in many groups which have not been intensively studied and in which cryptic species are difficult to detect. The existence of cryptic species demonstrates the lack of correlation between reproductive isolation and degree of morphological differentiation. Therefore the taxonomic treatment of morphologically similar, allopatric or allochronic populations must remain subjective and arbitrary until we have reliable criteria for predicting the evolutionary consequences of such populations becoming sympatric and synchronic.