Dynamics of periodical cicada chorus centers (Homoptera: Cicadidae:Magicicada)

Mating aggregations of three species of periodical cicadas were monitored during the emergence of Brood XIX at a 16-ha study site in northwest Arkansas, May–June 1985. Magicicada tredecassiniappeared first and formed the most choruses. M. tredecimand M. tredeculachoruses formed next, and M. tredeculachoruses outnumbered those of M. tredecim.Of the 268 choruses seen, 84% were composed of M. tredecassini. M. tredecassiniwere often found chorusing in the same trees with the other two species. Such multispecies mating aggregations apparently are unique to periodical cicadas. Choruses were dynamic with respect to their locations and durations. Initially, choruses were located near areas of high cicada emergence densities. One week later, cicadas chorused in trees throughout the forest and at the forest edge. Many choruses were seen only once at a location. Although cicadas chorused for almost 4 weeks, individual choruses persisted only approximately 8 days, on average. Sound intensities under chorus centers ranged from 50 to 80 dh and were correlated with arena sizes during times of peak chorus activity. No distinct habitat preferences of the three species were observed, however, the tree species used by chorusing cicadas differed among the species.     

Feeding ecology and evidence for amino acid synthesis in the periodical cicada (Magicicada)

The periodical cicadas of the genus Magicicada (including M. septendecim, M. cassini, and M. septendecula) have the longest juvenile life span of any insect, living underground for 13 or 17 years and feeding exclusively on root xylem fluids. Due to their inaccessible life cycles very little is known about cicada nutrition, despite the fact that members of Magicicada can achieve a very large biomass in woodland habitats east of the Mississippi and hence constitute a major part of the ecosystem where they occur in high densities. Live cicadas were collected at two sites in early June of 2004, during the emergence of Brood X (both M. septendecim and M. cassini were recovered). We used a combination of stable isotopic measurements (δ¹⁵N and δ¹³C) and multivariate statistical techniques to test for differences in resource acquisition among the cicada species and sexes collected at two locations within the 17-year periodical Brood X range. The amino acid constituents of cicada chitin and organs, plus xylem extracted from a deciduous sapling, were also analyzed. The data show that male and female cicadas have different carbon fractionations, which could reflect differential resource utilization due to oviposition in females. Several essential amino acids for the cicada were absent in xylem. Carbon-isotopic composition of all amino acids in the cicadas was distinctly different from the limited set measured in the xylem. Because of the differences in isotopic composition, we conclude that amino acids were synthesized de novo rather than incorporated directly, most likely produced by endosymbiotic bacteria.     

Comparative thermoregulation of sympatric endothermic and ectothermic cicadas (Homoptera: Cicadidae: Tibicen winnemanna and Tibicen chloromerus)

Measurements of body temperature in the field demonstrated that endothermic cicadas regulate body temperature by behavioral mechanisms as well as by endogenous heat production. Regression analysis suggests both endothermic and ectothermic species are thermoregulating. Body temperature of endothermically active cicadas without access to exogenous heat is approximately the same as the body temperature of basking cicadas. Tibicen winnemanna (Davis) raises body temperature in the field with the heat produced in flight or through the activation of the flight musculature without the act of flight. T. chloromerus (Walker) uses solar radiation to elevate body temperature to the level necessary for activity. The thermal responses of each species are related to its activity patterns with minimum flight temperature and shade-seeking temperatures significantly lower in the endothermic T. winnemanna. Heat torpor temperature appears to be related to the environment rather than behavior pattern. Endothermy in cicadas may serve to uncouple reproductive behavior from environmental constraints; to circumvent possible thermoregulatory problems; to permit the utilization of habitats unavailable to strictly ectothermic cicadas; to reduce predation; to optimize broadcast coverage and sound transmission; and to decrease possible acoustic interference. Accepted: 25 March 2000     

Thermoregulation and activity patterns of two syntopic cicadas,Tibicen chiricahua and T. duryi (Homoptera: Cicadidae), in central New Mexico

Summary Tibicen chiricahua and T. duryi are cicada species that are active as adults early each summer in central New Mexico, and are often syntopic in pinyon-juniper woodlands. Both species regulate thoracic temperature (T_th) within fairly narrow limits by utilizing behavioral mechanisms and evaporative cooling. However, syntopic populations of these two species were found to regulate at different T_th despite having synchronous annual and daily activity periods; overall mean T_th of T. chiricahua was 3.1°C higher than it was for T. duryi. Interspecific differences in evaporative cooling abilities and rates of passive heat exchange could not account for this difference in T_th. Part of the difference in T_th resulted from the fact that individuals of the two species were active in thermally distinct microhabitats. Within each species, mean T_th varied among behavior categories, and differences in how the two species allocated their time between activities also contributed to the interspecific difference in T_th. Though T. duryi is restricted to pinyon-juniper habitats such as the one in this study, T. chiricahua is also found in warmer habitats. The difference in T_th in the syntopic populations probably reflects interspecific differences in thermal preferences and thermal optima that are adaptive over their respective habitat ranges. The degree of dependence of T_th on ambient temperature (T_am) varied between activities within both species, with the least dependence exhibited during singing. Singing involves intense activity of tymbal muscles, which apparently can only function effectively over a relatively narrow range of temperature.     

Infectivity of resting spores of Massospora cicadina (Entomophthorales: Entomophthoraceae), an entomopathogenic fungus of periodical cicadas (Magicicada spp.) (Homoptera: Cicadidae)

Progeny of eastern oyster, Crassostrea virginica, introduced into France in 1992, were reared in IFREMER facilities to test their growth performances. During the summer of 1993, sporadic mass mortalities (80-90%) occurred among C. virginica spat reared in the IFREMER laboratories in La Tremblade (Charente Maritime, France) and Bouin (Vendée, France). Affected oysters presented mantle retraction and deposition of an anomalous conchiolin layer on the inner surface of the shell. The incidence of oysters with gross signs exceeded 80%. No obvious pathogen was identified in soft tissues by histology and transmission electron microscopy (TEM). However, histological examination showed the presence of anomalous basophilic round structures, 0.5-1 microm in diameter, in gill and mantle connective tissues. These extracellular Feulgen-negative structures reacted positively with the von Kossa stain. TEM examination on mantle and gill samples in diseased spat showed that the basophilic bodies consisted of concentric deposits of an amorphous substance interpreted as containing calcium. These observations may indicate that the mineralization process in spat shells was disturbed without exact determination of the cause. Based on the similarities of the gross signs to those reported in juvenile eastern oysters in the United States, we believe that the cause of the mortalities observed in France was probably the Juvenile Oyster Disease. Moreover, we report for the first time the detection of anomalous amorphous structures in gill and mantle connective tissues associated with mortalities and deposition of an anomalous conchioloin layer on the inner shell surface in C. virginica spat.     

Respiratory cooling in rattlesnakes

We used infrared thermography to study respiratory cooling in the rattlesnakes (Viperidae: Crotalinae) and to partition the effects of air temperature, humidity, and activity levels on head-body temperature differences. We observed a single, cooled region centered around the mouth and nasal capsule that extended across the pit membrane at air temperatures above 20 degrees C. Both head and body temperatures of rattlesnakes increased linearly with air temperature. Head-body temperature differentials also increased with air temperature, but declined significantly at higher relative humidities. Rattling rattlesnakes exhibited significantly greater head-body temperature differentials than did resting rattlesnakes. We suggest that respiratory cooling may provide a thermal buffer for the thermoreceptive pit organs at high air temperatures, but caution that this adaptive hypothesis must be tested with direct neural or behavioral assays.     

Eicosanoids mediate control of thermoregulatory sweating in the cicada,Tibicen dealbatus (Insecta: Homoptera)

Cicadas prevent body temperature from exceeding tolerable levels by a combination of behavioral responses and sweating. Sweating is activated when body temperature reaches a critical set-point temperature. We investigated control of sweating in the cicada, Tibicen dealbatus, by chemically manipulating biosynthesis of prostaglandins and other eicosanoids. Injecting prostaglandins in amounts equal to those that induce behavioral fever in scorpions and crustaceans resulted in only a small increase in set-point temperature. Blocking prostaglandin biosynthesis with cyclo-oxygenase inhibitors such as aspirin produced significant changes in set-point temperature, confirming that prostaglandins are involved in control of sweating. However, the effect of cyclo-oxygenase inhibitors was not the opposite of the effect of prostaglandins. Instead, the effect of cyclo-oxygenase inhibitors depended strongly on the value of setpoint temperature prior to treatment. Results of biochemical manipulations of other steps in eicosanoid biosynthetic pathways corroborated the results of cyclo-oxygenase inhibition and indicated that eicosanoids other than prostaglandins may be involved in control of body temperature in normothermic T. dealbatus. The effect of cyclo-oxygenase inhibitors on a given set-point temperature depended on the ambient temperature experienced by cicadas during the experiment. Surprisingly, cicadas exposed to ambient temperatures 40°C delayed activation of sweating until body temperature exceeded values normally recorded from T. dealbatus in the field. Control of body temperature in normothermic cicadas is thus complex, involving inputs from body temperature sensors, ambient temperature sensors, and at least two cyclo-oxygenase-dependent regulatory pathways.Abbreviations PUFA polyunsatured fatty acid(s) - T _a ambient temperature - T _b body temperature - T _set set-point of body temperature for activation of sweating     

The emergence of endothermy in the black-footed and Laysan albatrosses

Eggs with pip-holes of the black-footed (Diomedea nigripes) and Laysan (Diomedea immutabilis) albatrosses were exposed to various air temperatures in the range 20–35°C in order to detect signs of incipient endothermy in late embryos. No evidence of endothermy was found. In contrast, the O₂ consumption of most hatchlings increased in response to cooling, the O₂ consumption at an air temperature of 25° C exceeding that between 34 and 35°C by 40%. In a minority of hatchlings this response was not seen. It was suggested that endothermy may develop at some time during the 24 h after hatching.Abbreviations bm body mass - C _total total thermal conductance of tissues and plumage - f respiratory frequency - FE_{O 2} fractional concentration of oxygen in air leaving chamber - FI_{O 2} fractional concentration of oxygen in air entering chamber - T _a an temperature - T _b deep-body temperature - V air-flow rate - VO₂ oxygen consumption     

Thermal biology of Pacific cicada killers,Sphecius convallis Patton,in the Upper Sonoran Desert

A comprehensive investigation of the Pacific cicada killer, Sphecius convallis Patton, was undertaken to examine the behavioral and physiological mechanisms by which they are able to complete their life cycle in the thermal extremes of the Upper Sonoran Desert. S. convallis were endothermic, exhibiting elevated and relatively constant thorax temperatures during many activities. Males basked in trees at dawn to warm up, then used a variety of behaviors and perching strategies to maintain thorax temperature during territorial behavior. The thorax temperature of females was highest during provisioning and orientation flights, somewhat lower while investigating burrows, and lowest while digging burrows. The optimal thorax temperature for flight was about 40 °C, which was approximated most closely by males resting in the shade during the afternoon. In mating clusters, the mated male was the hottest, the female was coolest and the other males were intermediate. Wasps lost about 5% of body mass during heating treatments, and may use evaporative water loss for cooling. Pacific cicada killers use a complex suite of behavioral and physiological adaptations to regulate body temperature during their nesting season.     

Red-winged blackbird predation on periodical cicadas (Cicadidae: Magicicada spp.): bird behavior and cicada responses

Summary Predation by red-winged blackbirds Agelaius phoeniceus L. on 13-year periodical cicadas (Magicicada spp.) and reactions by periodical cicadas to predators were studied during emergence of Brood XIX during summer of 1985 in northwestern Arkansas (USA). Emergences of periodical cicadas are classic examples of predator satiation due to high local densities of cicadas and birds are the major predators of adult periodical cicadas. Reactions of periodical cicadas to predators were assessed by recording behaviors exhibited by cicadas when approached in trees by a human hand during the 3-week period of peak adult densitics. Most male cicadas made a noise in association with escape behaviors when approached, and 50% of the females, which are silent, attempted escape behaviors. Observations of predation attempts on cicadas by red-winged blackbirds were made during the period of peak predation pressure. Red-winged blackbirds spent less time searching for cicadas over that 2-week period of increasing predation pressure, and became increasingly efficient at capturing cicadas. Handling time of cicadas by red-winged blackbirds increased by about 20 seconds over that period, as blackbirds spent more time consuming female cicadas. The flysquawk response, used only by male cicadas, was effective in deterring red-winged blackbirds; only 5% of the attacks by blackbirds were successful when that behavior was exhibited. All cicadas that remained motionless and silent when approached by blackbirds were captured and consumed. Because females remained inactive when approached more often than did males, blackbirds may have consumed more female cicadas. Changes that appeared in reactions of preiodical cicadas to the model predator and to the attacks of blackbirds reflect both changes in the sex ratio of the cicada populations and changes in behaviors of cicadas associated with mating and egg laying. The loud noise made by male periodical cicadas at mating centers did not appear to deter predation by blackbirds. Changes in the behavior of blackbirds that appeared to be in association with greater predation on female periodical cicadas relates directly to aspects of foraging theory, particularly predictions concerning more selective foraging during periods of abundant food resources.     

Diurnal activity, temperature responses and endothermy in three South American cicadas (Homoptera: Cicadidae: Dorisiana bonaerensis, Quesada gigas and Fidicina mannifera)

1. 1. Measurements of body temperature (T_b) in the field demonstrated that endothermic cicadas regulate T_b by behavioral mechanisms as well as by endogenous heat production.

2. 2. The T_b of endothermically active cicadas without access to exogenous heat is approximately the same as the T_b of basking cicadas.

3. 3. Dorisiana bonaerensis (Berg) and Quesada gigas (Olivier) raise T_b in the field with the heat produced in flight.

4. 4. The thermal responses of a particular species are related to its activity patterns and habitat.

5. 5. Endothermy in cicadas may serve to uncouple reproductive behavior from environmental constraints; to circumvent possible thermoregulatory problems; to permit the utilization of habitats unavailable to strictly ectothermic cicadas; to reduce predation; and to optimize broadcast coverage and sound transmission.

     

Body temperature and the acoustic behavior of the cicadaTibicen winnemanna (Homoptera: Cicadidae)

Tibicen winnemanna (Davis) produces a broad-band frequency- and amplitude-modulated advertisement call. Observations of the animals in the field show that the cicadas produce varied acoustic output. This work investigates the connection between the acoustic behavior of the cicada and the body temperature of the calling animal. The results show there is strong evidence to support the hypothesis that both acoustic output and song intensity are highly dependent on body temperature.     

Central projections of fibers in the auditory and tensor nerves of cicadas (Homoptera: Cicadidae)

Summary The auditory and tensor nerves of cicadas are mixed nerves containing both afferent and efferent elements. In 17-year cicadas, and in Okanagana rimosa, the auditory nerve contains afferents from body hairs, from the detensor tympani-chordotonal organ, and some 1300–1500 afferents from the hearing organ. Within the fused metathoracic-abdominal ganglionic complex the receptors from both the auditory and tensor nerves form a neuropilar structure that reveals the metameric organization of this complex. A few fibers run anteriorly, projecting into the meso and prothoracic ganglia. Within the ganglionic complex a division of auditory nerve afferents into a dense intermediate and a more diffuse ventral neuropile is observed. In addition, a dorsal motor neuropile is outlined by arborizations of the timbal motor neuron. This neuron is one of several efferent cell types associated with the auditory nerve, and there is an indication that several efferent fibers innervate the timbal muscle. There is anatomical evidence for a possible neuronal coupling between the bilaterally symmetrical large timbal motor neurons. In general, central projections from the auditory and tensor nerves support evidence of a structural layering within the CNS of insects.     

A light and transmission electron microscope study of some cells and tissues associated with the tymbal muscle of a periodical cicada (Homoptera, Cicadidae)

Abstract. A light and transmission electron microscope study of sections of cells of—and of cells and tissues of—and of cells, associated with the previously undescribed tymbal muscle of a periodical cicada (Brood X of the 17-year cicada) was undertaken to (i) compare their features with similar features described for other cicada tymbal muscles, (ii) use that information to try to determine cytologically whether the muscle should be considered synchronous or asynchronous, and (iii) seek information about ultrastructural features not previously described for any cicada. In cross section the myofibrils are slightly angular and have an abundance of sarcoplasmic reticulum and T tubules. Longitudinal sections show a pair of T tubules, one of each pair located midway between the Z line and the center (H level) of each sarcomere. These cytological features are consistently found in the tymbal muscles of the majority of other cicada genera and species, which are designated synchronous muscles, and all of which are termed fast muscles. The amount of sarcoplasmic reticulum increases at the Z lines. The largest mitochondria occur in the largest axons, but the smallest axons have more neurotubules per cross-section area. Axon diameters range 0.14–20 μm. Multinucleate adipocytes, with vacuoles that appear either empty or content-containing, and tracheocytes, which could either be binucleate or have a lobate or U-shaped nucleus, are located at the periphery of the muscle. Large numbers of microtubules occur in the interface glia. The diameters of microtubules and neurotubules (∼27 nm) agree closely with the averages usually cited. This study indicates that the tymbal muscles of this cicada should be designated as synchronous, and it describes ultrastructural features that are typical and others that are unusual.     

Heterorhabditis sonorensis n. sp. (Nematoda: Heterorhabditidae), a natural pathogen of the seasonal cicada Diceroprocta ornea (Walker) (Homoptera: Cicadidae) in the Sonoran desert

A new Heterorhabditis species was isolated from nymphal stages of the seasonal cicada Diceroprocta ornea (Walker) in an asparagus field in the state of Sonora, Mexico. Concomitantly, another isolate of the same nematode species was also collected from an oak woodland habitat in the Chiricahua mountain range in southeastern Arizona. Morphological and molecular studies together with cross-hybridization tests indicate these two isolates are conspecific and represent a new undescribed Heterorhabditis sp. This new species is distinguished from other species in this genus by a combination of several qualitative and quantitative morphological traits. Key diagnostic features include: presence of a pronounced post-anal swelling in the hermaphrodite; male with nine pairs of bursal rays, with pairs 4 and 7 bent outwards and one pair of papillae placed on the cloacal opening, value of D% (average: 79); infective juveniles with a well developed cuticular tooth, long tail (average: 105 μm) and values of D% (average: 90) and E% (average: 99). In addition to these diagnostic characters, cross-hybridization tests between the new species with H. bacteriophora and H. mexicana yielded no fertile progeny. Comparison of ITS rDNA sequences with other available sequences of described species depicted the two isolates as a new species. Phylogenetic analysis of these sequence data placed H. sonorensis n. sp. as a member of the indica-group.     

Thermoregulation and the effect of body temperature on call temporal parameters in the cicada Diceroprocta olympusa (Homoptera: Cicadidae)

We investigated the thermoregulatory behavior, thermal responses (minimum flight, maximum voluntary tolerance and heat torpor temperatures) and the effect of body temperature (T(b)) on call parameters in the cicada Diceroprocta olympusa (Walker). Regression of T(b) as a function of ambient (T(a)) or perch temperatures (T(p)) suggests thermoregulation is occurring. Thermoregulation occurs through behavioral changes that alter the uptake of solar radiation. T(p) is a better predictor of T(b) than is T(a). Thermal responses (minimum flight temperature 20.4 degrees C, maximum voluntary tolerance temperature 37 degrees C, and heat torpor temperature 46.7 degrees C) may be related to the humid, grassland habitat of the species. In contrast to other acoustic insects, no significant relationship was found between the temporal parameters of the calling song and T(b) within the population of D. olympusa.     

Reproductive character displacement and speciation in periodical cicadas, with description of new species, 13-year Magicicada neotredecem

Abstract. Acoustic mate-attracting signals of related sympatric, synchronic species are always distinguishable, but those of related allopatric species sometimes are not, thus suggesting that such signals may evolve to "reinforce" premating species isolation when similar species become sympatric. This hypothesis predicts divergences restricted to regions of sympatry in partially overlapping species, but such "reproductive character displacement" has rarely been confirmed. We report such a case in the acoustic signals of a previously unrecognized 13-year periodical cicada species, Magicicada neotredecim , described here as a new species (see Appendix). Where M. neotredecim overlaps M. tredecim in the central United States, the dominant male call pitch (frequency) of M. neotredecim increases from approximately 1.4 kHz to 1.7 kHz, whereas that of M. tredecim remains comparatively stable. The average preferences of female M. neotredecim for call pitch show a similar geographic pattern, changing with the call pitch of conspecific males. Magicicada neotredecim differs from 13-year M. tredecim in abdomen coloration, mitochondrial DNA, and call pitch, but is not consistently distinguishable from 17-year M. septendecim ; thus, like other Magicicada species, M. neotredecim appears most closely related to a geographically adjacent counterpart with the alternative life cycle. Speciation in Magicicada may be facilitated by life-cycle changes that create temporal isolation, and reinforcement could play a role by fostering divergence in premating signals prior to speciation. We present two theories of Magicicada speciation by life-cycle evolution: "nurse-brood facilitation" and "life-cycle canalization."     

Suitability of Aphis fabae, Myzus persicae (Homoptera: Aphididae) and Aleyrodes proletella (Homoptera: Aleyrodidae) as prey for Coccinella undecimpunctata (Coleoptera: Coccinellidae)

The suitability of Aphis fabae Scopoli, Myzus persicae Sulzer and Aleyrodes proletella L. as food sources for Coccinella undecimpunctata L. was evaluated by studying the impact of prey consumption on the predator’s population growth parameters and feeding parameters. Unlike A. proletella, A. fabae and M. persicae supported the development and reproduction of C. undecimpunctata. A. fabae and M. persicae were considered to be essential prey, whereas A. proletella was considered to be an alternative prey. Aphid species showed different degrees of suitability: M. persicae significantly decreased the pre-oviposition period and increased adult longevity, fecundity and fertility compared with A. fabae. Moreover, A. fabae represents a suitable diet for larval development, but is not a suitable food source for adult reproduction. The predator’s population growth parameters, R₀, r_m and λ were increased with M. persicae, whereas T decreased. We found that the 4th instar larvae were the most voracious, particularly when fed on M. persicae; nevertheless, with this prey daily weight gain and feeding efficiency of 4th instar larvae were similar to that of individuals fed with A. fabae.