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Abstract Periodical cicadas are remarkable for their incredibly long, prime-numbered life cycles and almost perfectly synchronized mass emergence. Synchronized emergence is a generally localized event, referred to as a “brood”. Broods are separated in space and time, or parapatric; adjacent broods emerge on different schedules, whereas some cicadas emerge off schedule, called stragglers. Straggling can potentially erode brood boundaries; thus, the mechanism allowing broods to maintain nonoverlapping distributions is highly puzzling. Here, we propose that predation may allow broods to exclude each other. Our model and numerical simulations show that predation could act as an important factor for maintaining the nonoverlapping distributions. The proposed mechanism is most effective in the vicinity of the critical strength of predation, beyond which the population is doomed to extinction. An increase in predation intensity increases resistance to settlement of a minority brood, while suppressing the main brood population.

Periodical cicadas are remarkable for their incredibly long, prime-numbered life cycles and almost perfectly synchronized mass emergence. Synchronized emergence is a generally localized event, referred to as a "brood". Broods are separated in space and time, or parapatric; adjacent broods emerge on different schedules, whereas some cicadas emerge off schedule, called stragglers. Straggling can potentially erode brood boundaries; thus, the mechanism allowing broods to maintain nonoverlapping distributions is highly puzzling. Here, we propose that predation may allow broods to exclude each other. Our model and numerical simulations show that predation could act as an important factor for maintaining the nonoverlapping distributions. The proposed mechanism is most effective in the vicinity of the critical strength of predation, beyond which the population is doomed to extinction. An increase in predation intensity increases resistance to settlement of a minority brood, while suppressing the main brood population. [ABSTRACT FROM AUTHOR]

The fungal genus Massospora (Zoopagomycota: Entomophthorales) includes more than a dozen obligate, sexually transmissible pathogenic species that infect cicadas (Hemiptera) worldwide. At least two species are known to produce psychoactive compounds during infection, which has garnered considerable interest for this enigmatic genus. As with many Entomophthorales, the evolutionary relationships and host associations of Massospora spp. are not well understood. The acquisition of M. diceroproctae from Arizona, M. tettigatis from Chile, and M. platypediae from California and Colorado provided an opportunity to conduct molecular phylogenetic analyses and morphological studies to investigate whether these fungi represent a monophyletic group and delimit species boundaries. In a three-locus phylogenetic analysis including the D1-D2 domains of the nuclear 28S rRNA gene (28S), elongation factor 1 alpha-like (EFL), and beta-tubulin (BTUB), Massospora was resolved in a strongly supported monophyletic group containing four well-supported genealogically exclusive lineages, based on two of three methods of phylogenetic inference. There was incongruence among the single-gene trees: two methods of phylogenetic inference recovered trees with either the same topology as the three-gene concatenated tree (EFL) or a basal polytomy (28S, BTUB). Massospora levispora and M. platypediae isolates formed a single lineage in all analyses and are synonymized here as M. levispora. Massospora diceroproctae was sister to M. cicadina in all three single-gene trees and on an extremely long branch relative to the other Massospora, and even the outgroup taxa, which may reflect an accelerated rate of molecular evolution and/or incomplete taxon sampling. The results of the morphological study presented here indicate that spore measurements may not be phylogenetically or diagnostically informative. Despite recent advances in understanding the ecology of Massospora, much about its host range and diversity remains unexplored. The emerging phylogenetic framework can provide a foundation for exploring coevolutionary relationships with cicada hosts and the evolution of behavior-altering compounds.

Entomopathogenic fungi routinely kill their hosts before releasing infectious spores, but a few species keep insects alive while sporulating, which enhances dispersal. Transcriptomics- and metabolomics-based studies of entomopathogens with post-mortem dissemination from their parasitized hosts have unraveled infection processes and host responses. However, the mechanisms underlying active spore transmission by Entomophthoralean fungi in living insects remain elusive. Here we report the discovery, through metabolomics, of the plant-associated amphetamine, cathinone, in four Massospora cicadina-infected periodical cicada populations, and the mushroom-associated tryptamine, psilocybin, in annual cicadas infected with Massospora platypediae or Massospora levispora, which likely represent a single fungal species. The absence of some fungal enzymes necessary for cathinone and psilocybin biosynthesis along with the inability to detect intermediate metabolites or gene orthologs are consistent with possibly novel biosynthesis pathways in Massospora. The neurogenic activities of these compounds suggest the extended phenotype of Massospora that modifies cicada behavior to maximize dissemination is chemically-induced.

The periodical cicadas of the genus Magicicada Davis, 1925 inhabiting eastern United States are characterized by a long juvenile period of 17 or 13 years and periodical mass emergence of adults. In this genus, only seven species are distinguished and are distributed into three species groups, Decim, Cassini and Decula. We performed comparative cytogenetic study of all seven Magicicada species, and 6 of them were explored for the first time. The techniques used included standard chromosome staining, differential chromosome staining techniques (C-banding, AgNOR-banding and fluorochrome DAPI-staining) and FISH (fluorescence in situ hybridization) with 18S rDNA and (TTAGG)n-telomeric probes. All these species have holokinetic chromosomes, like other Hemiptera. Karyotypes of all species appeared to be remarkably conserved with 2n = 19/20 (18 + X0/XX) (male/female); one very large pair of autosomes and all other chromosomes constituting a decreasing size series; X chromosomes were indistinguishable, at least, at mitotic metaphases. The nucleolus organizer regions (NORs) revealed on one of the medium-sized chromosome pairs in all species and were shown to coincide with the rDNA clusters revealed by FISH. In all species, very small blocks of C-heterochromatin were variously located on chromosomes clearly using DAPI but less distinctly by C-banding. The chromosomes of all the species studied were confirmed to contain the "insect type" motif of telomeres (TTAGG)n.

Abstract We investigate competition between separate periodical cicada populations each possessing different life‐cycle lengths. We build an individual‐based model to simulate the cicada life cycle and allow random migrations to occur between patches inhabited by the different populations. We show that if hybridization between different cycle lengths produces offspring that have an intermediate life‐cycle length, then predation acts disproportionately to select against the hybrid offspring. This happens because they emerge in low densities without the safety‐in‐numbers provided by either parent population. Thus, prime‐numbered life cycles that can better avoid hybridization are favored. However, we find that this advantage of prime‐numbered cycles occurs only if there is some mechanism that can occasionally synchronize emergence between local populations in sufficiently many patches.

Periodical cicadas (Magicicada spp.) mature in 13 or 17 years, the longest development times for any non-diapausing insects. Selection may favor prolonged development since nymphs experience little mortality and individuals taking 17 years have been shown to have greater fecundity than those taking 13 years. Why don't periodical cicadas take even longer to develop? Nymphs feed on root xylem fluid and move little. Ovipositing females prefer fast-growing trees at forest edges. I hypothesized that (1) adults emerging at edges would be heavier than those from forest interiors and (2) habitat changes could limit development time. I collected newly eclosed females that had neither fed as adults nor moved from their site of development. For M. septendecim, females from edges were 4.9% heavier than those from the interior. I assumed that emergence density indicated habitat quality and measured density at eight sites in 1979, 1996, and 2013. Over three generations, variation in densities was great; densities at two sites crashed, and at one site they exploded to 579/m2 Habitat transience may limit development time because only adults can reassess habitats and reposition offspring. In conclusion, cicadas are affected by habitat characteristics, habitats change over 17 years, and cicadas may emerge, mate, and redistribute their offspring to track habitat dynamics.

The appearance of periodical cicadas, Magicicada Davis spp. (Hemiptera: Cicadidae), in the United States has been a source of wonder, confusion, and consternation from the time of colonization to the present. The ability to forecast the emergence of periodical cicadas has practical implications to homeowners, urban foresters, nursery growers, and orchardists trying to protect young trees from cicada damage, and to educators and the media as they teach and inform diverse audiences. By linking large numbers of cicada sightings collected on cellular phones by citizen scientists using the Cicada Safari app with widely available web-based weather data, we define dates, days of the year, and accumulated degree days for sightings of 17-year Brood X straggler cicadas. We present a procedure for coupling observations made by citizen scientists with data from weather stations to track patterns of cicada emergence which may have applicability throughout the range of periodical cicadas in the United States. [ABSTRACT FROM AUTHOR]

Differences in number and arrival time of male and female adult periodical cicadas, Magicicada septendecim (Linnaeus), Brood X, in a small geographic area of Maryland in 2004, are described and discussed. Newly emergent cicadas were counted, by sex, along various suburban streets. A probable incidence of protandry--the arrival of adult males before adult females--was observed. Data analyses by test of proportions show that for some of the first days of counting, in one of the two sample sites and in both sites combined, the disproportionate appearance of adult males was statistically significant, while for the last few days, the disproportionate appearance of adult females was also statistically significant. In one of the two sites and in both sites combined, significantly more females than males for the season as a whole were also observed. Though this study appears to confirm previous findings, there is little discussion in the literature on protandry in periodical cicadas, and no other study on this subject and species with detailed methodology for sampling, that avoids double counting. It might be useful to conduct field counts of periodical cicadas in other locations to discover where such protandry may or may not occur. It is believed that this mode of protandry is adaptive for the species, and that it evolved to enhance survivability or reproductive opportunity for both sexes. [ABSTRACT FROM AUTHOR]

We investigate competition between separate periodical cicada populations each possessing different life‐cycle lengths. We build an individual‐based model to simulate the cicada life cycle and allow random migrations to occur between patches inhabited by the different populations. We show that if hybridization between different cycle lengths produces offspring that have an intermediate life‐cycle length, then predation acts disproportionately to select against the hybrid offspring. This happens because they emerge in low densities without the safety‐in‐numbers provided by either parent population. Thus, prime‐numbered life cycles that can better avoid hybridization are favored. However, we find that this advantage of prime‐numbered cycles occurs only if there is some mechanism that can occasionally synchronize emergence between local populations in sufficiently many patches. [ABSTRACT FROM AUTHOR]

Mathematics appears to play a genuine explanatory role in science. But how do mathematical explanations work? Recently, a counterfactual approach to mathematical explanation has been suggested. I argue that such a view fails to differentiate the explanatory uses of mathematics within science from the non-explanatory uses. I go on to offer a solution to this problem by combining elements of the counterfactual theory of explanation with elements of a unification theory of explanation. The result is a theory according to which a counterfactual is explanatory when it is an instance of a generalized counterfactual scheme. [ABSTRACT FROM AUTHOR]

We used 37 years of North American Breeding Bird Surveys to test for effects of periodical cicada (Magicicada spp.) emergences on the abundance and spatial synchrony of 24 species of avian predators in hardwood forests of the eastern United States. Fifteen (63%) of the bird species exhibited numerical changes in abundance apparently associated with emergences of the local periodical cicada brood, and intraspecific spatial synchrony of bird abundance was significantly greater between populations sharing the same cicada brood than between populations in the ranges of different broods. Species exhibited at least four partially overlapping temporal patterns. (I) Cuckoos (Coccyzus spp.) occurred in high numbers only during emergence years and subsequently declined in abundance. (2) Red-bellied Woodpeckers (Melanerpes carolinus), Blue Jays (Cyanocitta cristata), Common Grackles (Quiscalus quiscula), and Brown-headed Cowbirds (Molothrus ater) increased significantly 1-3 years following emergences and then declined. (3) Red-headed Woodpeckers (Melanerpes erythrocephalus), American Crows (Corvus brachyrynchos), Tufted Titmice (Baeolophus bicolor), Gray Catbirds (Dumetella carolinensis), and Brown Thrashers (Toxostoma rufum) were found in significantly low numbers during emergence years, underwent significant numerical increases in the following year, and then stabilized. (4) Wood Thrushes (Hylocichla mustelina), Northern Mockingbirds (Mimus polyglottos), Northern Cardinals (Cardinalis cardinalis), and House Sparrows (Passer domesticus) exhibited significantly deviant population numbers 1-2 years prior to emergences, below the long-term mean in the first two species and above the long-term mean in the latter two. These results suggest that the pulses of resources available at 13- or 17-year intervals when periodical cicadas emerge have significant demographic effects on key avian predators, mostly during or immediately after emergences, but in some cases apparently years following emergence events.

Entomopathogenic fungi routinely kill their hosts before releasing infectious spores, but a few species keep insects alive while sporulating, which enhances dispersal. Transcriptomics- and metabolomics-based studies of entomopathogens with post-mortem dissemination from their parasitized hosts have unraveled infection processes and host responses. However, the mechanisms underlying active spore transmission by Entomophthoralean fungi in living insects remain elusive. Here we report the discovery, through metabolomics, of the plant-associated amphetamine, cathinone, in four Massospora cicadina -infected periodical cicada populations, and the mushroom-associated tryptamine, psilocybin, in annual cicadas infected with Massospora platypediae or Massospora levispora , which likely represent a single fungal species. The absence of some fungal enzymes necessary for cathinone and psilocybin biosynthesis along with the inability to detect intermediate metabolites or gene orthologs are consistent with possibly novel biosynthesis pathways in Massospora. The neurogenic activities of these compounds suggest the extended phenotype of Massospora that modifies cicada behavior to maximize dissemination is chemically-induced. [ABSTRACT FROM AUTHOR]

It has been previously hypothesized that the perfectly synchronized mass emergence of periodical cicadas (Magicicada spp.) evolved as a result of a switch from size-based to age-based emergence. In the former case, cicada nymphs emerge immediately (at the first opportunity) on reaching maturity, whereas in the latter case, nymphs wait in order to emerge at a specific age. Here we use an individual-based model to simulate the cicada life cycle and to study the evolution of periodicity. We find that if age-based emergence evolves in a constant abiotic environment, it typically results in a population that is protoperiodic, and synchronous emergence of the whole population is not achieved. However, perfect periodicity and synchronous emergence can be attained, if the abiotic environment changes back and forth between favorable and unfavorable conditions (hysteresis). Furthermore, once age-based emergence evolves, generally it can only be invaded by other age-based emergence strategies with longer cycle lengths (evolutionary ratchet). Together, these mechanisms promote the evolution of long periodic life cycles and synchronous emergence in the Magicicada. We discuss how our results connect to previous theories and recent phylogenetic studies on Magicicada evolution. [ABSTRACT FROM AUTHOR]

The mass application of whole mitogenome (MG) sequencing has great potential for resolving complex phylogeographic patterns that cannot be resolved by partial mitogenomic sequences or nuclear markers. North American periodical cicadas (Magicicada) are well known for their periodical mass emergence at 17- and 13-year intervals in the north and south, respectively. Magicicada comprises three species groups, each containing one 17-year species and one or two 13-year species. Within each life cycle, single-aged cohorts, called broods, of periodical cicadas emerge in different years, and most broods contain members of all three species groups. There are 12 and three extant broods of 17- and 13-year cicadas, respectively. The phylogeographic relationships among the populations and broods within the species groups have not been clearly resolved. We analyzed 125 whole MG sequences from all broods and seven species within three species groups to ascertain the divergence history of the geographic and allochronic populations and their life cycles. Our mitogenomic phylogeny analysis clearly revealed that each of the three species groups had largely similar phylogeographic subdivisions (east, middle, and west) and demographic histories (rapid population expansion after the last glacial period). The mitogenomic phylogeny also partly resolved the brood diversification process, which could be explained by hypothetical temporary life cycle shifts, and showed that none of the 13- and 17-year species within the species groups was monophyletic, possibly due to gene flow between them. Our findings clearly reveal phylogeographic structures in the three Magicicada species groups, demonstrating the advantage of whole MG sequence data in phylogeographic studies. [ABSTRACT FROM AUTHOR]

The Enhanced Indispensability Argument (EIA) appeals to the existence of Mathematical Explanations of Physical Phenomena (MEPPs) to justify mathematical Platonism, following the principle of Inference to the Best Explanation. In this paper, I examine one example of a MEPP—the explanation of the 13-year and 17-year life cycle of magicicadas—and argue that this case cannot be used defend the EIA. I then generalize my analysis of the cicada case to other MEPPs, and show that these explanations rely on what I will call 'optimal representations', which are representations that capture all that is relevant to explain a physical phenomenon at a specified level of description. In the end, because the role of mathematics in MEPPs is ultimately representational, they cannot be used to support mathematical Platonism. I finish the paper by addressing the claim, advanced by many EIA defendants, that quantification over mathematical objects results in explanations that have more theoretical virtues, especially that they are more general and modally stronger than alternative explanations. I will show that the EIA cannot be successfully defended by appealing to these notions. [ABSTRACT FROM AUTHOR]

Periodical cicadas, known for strict life-cycle lengths of 13 or 17 yr, actually exhibit developmental plasticity in cycle length. This variation tends to occur in 1- and 4-yr increments for both life-cycle types, with the largest events involving 4-yr accelerations of the 17-yr species. The pattern has stimulated hypotheses to explain brood formation and life-cycle evolution, but most of the evidence is anecdotal. We present the first quantitative evidence confirming that a site with a 4-yr acceleration does not necessarily experience comparable emergence in the following year, and we provide the first density estimate for a 4-yr early emergence of 17-yr cicadas (1.28/m2, within the range of published estimates for on-schedule emergences). We also document a 4-yr early 13-yr emergence--cicadas apparently emerging in 9 yr. Multimodal life-cycle patterns spanning -4 to +4 yr are evident in both 13- and 17-yr cicadas. [ABSTRACT FROM AUTHOR]

Periodical cicadas, known for strict life-cycle lengths of 13 or 17 yr, actually exhibit developmental plasticity in cycle length. This variation tends to occur in 1- and 4-yr increments for both life-cycle types, with the largest events involving 4-yr accelerations of the 17-yr species. The pattern has stimulated hypotheses to explain brood formation and life-cycle evolution, but most of the evidence is anecdotal. We present the first quantitative evidence confirming that a site with a 4-yr acceleration does not necessarily experience comparable emergence in the following year, and we provide the first density estimate for a 4-yr early emergence of 17-yr cicadas (1.28/m2, within the range of published estimates for on-schedule emergences). We also document a 4-yr early 13-yr emergence-cicadas apparently emerging in 9 yr. Multimodal life-cycle patterns spanning −4 to +4 yr are evident in both 13- and 17-yr cicadas. [ABSTRACT FROM AUTHOR]

We describe and illustrate the biogeography of the cicadas inhabiting continental North America, north of Mexico. Species distributions were determined through our collecting efforts as well as label data from more than 110 institutional collections. The status of subspecies is discussed with respect to their distributions. As we have shown over limited geographic areas, the distribution of individual species is related to the habitat in which they are found. We discuss the biogeography of the genera with respect to their phylogenetic relationships. California is the state with the greatest alpha diversity (89 species, 46.6% of taxa) and unique species (35 species, 18.3% of taxa). Texas, Arizona, Colorado and Utah are the states with the next greatest alpha diversity with Texas, Arizona and Utah being next for unique species diversity. Maine, New Hampshire and Rhode Island are the states with the least amount of cicada diversity. Diversity is greatest in states and areas where there is a diversity of plant communities and habitats within these communities. Mountainous terrain also coincides with increases in diversity. Several regions of the focus area require additional collection efforts to fill in the distributions of several species.

The article discusses a geographic information system (GIS) based periodical cicadas (Magicicada) brood map developed by the authors to examine the population of Magicicadas around Illinois. Topics discussed include the brood distribution of Magicicadas around Illinois and other portions of surrounding states, the authors collecting the local data using Global Positioning System (GPS) units, and the difference between authors' map and a map developed by entomologist Charles Marlatt in 1923.

Seven species in three species groups (Decim, Cassini and Decula) of periodical cicadas ( Magicicada) occupy a wide latitudinal range in the eastern United States. To clarify how adult body size, a key trait affecting fitness, varies geographically with climate conditions and life cycle, we analysed the relationships of population mean head width to geographic variables (latitude, longitude, altitude), habitat annual mean temperature (AMT), life cycle and species differences. Within species, body size was larger in females than males and decreased with increasing latitude (and decreasing habitat AMT), following the converse Bergmann's rule. For the pair of recently diverged 13- and 17-year species in each group, 13-year cicadas were equal in size or slightly smaller on average than their 17-year counterparts despite their shorter developmental time. This fact suggests that, under the same climatic conditions, 17-year cicadas have lowered growth rates compared to their 13-years counterparts, allowing 13-year cicadas with faster growth rates to achieve body sizes equivalent to those of their 17-year counterparts at the same locations. However, in the Decim group, which includes two 13-year species, the more southerly, anciently diverged 13-year species ( Magicicada tredecim) was characterized by a larger body size than the other, more northerly 13- and 17-year species, suggesting that local adaptation in warmer habitats may ultimately lead to evolution of larger body sizes. Our results demonstrate how geographic clines in body size may be maintained in sister species possessing different life cycles. [ABSTRACT FROM AUTHOR]

The article discusses the emergence of periodical cicada in the Eastern North America. It mentions that periodical cicadas are grouped into broods based on the calendar year when they emerge. It offers information on periodical cicada mapping project which aims to produce conservative maps of periodical cicada broods that may be used as a baseline for detecting range changes concerning brood and species formation.

An introduction to articles in the issue is presented on topics including observations during the 2021 emergence of the Brood X 17-year periodical cicada, Magicicada Davis, 2015 yearlong bee survey on the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island in the Chesapeake Bay, and the Scarabaeoidea of the George Washington Memorial Parkway.

Periodical cicadas in the genus Magicicada Davis (Hemiptera: Cicadidae) of brood II emerged in the eastern United States of America in 2013. In Connecticut, only Magicicada septendecim (Linnaeus) had been recorded until this emergence when Magicicada septendecula Alexander and Moore was found on Totoket Mountain in North Branford, Connecticut, United States of America. This discovery represented the northeastern-most record of this species. In two 0.25-ha plots where M. septendecula and M. septendecim emerged and chorused, species of Carya Nuttall (Juglandaceae) comprised 59.9–63.7% of the total basal area, with Carya glabra (Miller) Sweet, accounting for 43.9–60.0%. In one plot, 31.6% of the total basal area was Fraxinus americana Linnaeus (Oleaceae). By using the proportion of exuviae of M. septendecula (hind tibial length<6.3 mm) and M. septendecim (length ⩾ 6.3 mm) near trees and the mean number of emergence holes per 0.25-m2 quadrat (1.88), it was estimated that 1487 M. septendecula and 17 313 M. septendecim emerged in one 0.25-ha plot. Mean tibial length of M. septendecula was significantly smaller in males (5.53 mm) than females (5.99 mm), and the sex ratio did not depart significantly from 1:1. Magicicada septendecula may be threatened by the decline of F. americana and Juglans cinerea Linnaeus (Juglandaceae), the first a known host and the second a suspected host. [ABSTRACT FROM PUBLISHER]

We describe and illustrate the biogeography of the cicadas inhabiting continental North America, north of Mexico. Species distributions were determined through our collecting efforts as well as label data from more than 110 institutional collections. The status of subspecies is discussed with respect to their distributions. As we have shown over limited geographic areas, the distribution of individual species is related to the habitat in which they are found. We discuss the biogeography of the genera with respect to their phylogenetic relationships. California is the state with the greatest alpha diversity (89 species, 46.6% of taxa) and unique species (35 species, 18.3% of taxa). Texas, Arizona, Colorado and Utah are the states with the next greatest alpha diversity with Texas, Arizona and Utah being next for unique species diversity. Maine, New Hampshire and Rhode Island are the states with the least amount of cicada diversity. Diversity is greatest in states and areas where there is a diversity of plant communities and habitats within these communities. Mountainous terrain also coincides with increases in diversity. Several regions of the focus area require additional collection efforts to fill in the distributions of several species. [ABSTRACT FROM AUTHOR]

The extraordinarily long life cycles, synchronous emergences at 13- or 17-year intervals, and complex geographic distribution of periodical cicadas (Magicicada spp.) in eastern North America are a long-standing evolutionary enigma. Although a variety of factors, including satiation of aboveground predators and avoidance of interbrood hybridization, have been hypothesized to shape the evolution of this system, no empirical support for these mechanisms has previously been reported, beyond the observation that bird predation can extirpate small, experimentally mistimed emergences. Here we show that periodical cicada emergences appear to set populations of potential avian predators on numerical trajectories that result in significantly lower potential predation pressure during the subsequent emergence. This result provides new support for the importance of predators in shaping periodical cicada life history, offers an ecological rationale for why emergences are synchronized at the observed multiyear intervals, and may explain some of the developmental plasticity observed in these unique insects. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Baker () claims to provide an example of mathematical explanation of an empirical phenomenon which leads to ontological commitment to mathematical objects. This is meant to show that the positing of mathematical entities is necessary for satisfactory scientific explanations and thus that the application of mathematics to science can be used, at least in some cases, to support mathematical realism. In this paper I show that the example of explanation Baker considers can actually be given without postulating mathematical objects and thus cannot be used by the mathematical realist. I also show that, despite this, mathematics keeps playing an important methodological role in the explanation and does not reduce to a merely computational or descriptive framework. [ABSTRACT FROM AUTHOR]

Periodical cicadas are well known for their prime-numbered life cycles (17 and 13 years) and their mass periodical emergences. The origination and persistence of prime-numbered cycles are explained by the hybridization hypothesis on the basis of their lower likelihood of hybridization with other cycles. Recently, we showed by using an integer-based numerical model that prime-numbered cycles are indeed selected for among 10-to 20-year cycles. Here, we develop a real-number-based model to investigate the factors affecting the selection of prime-numbered cycles. We include an Allee effect in our model, such that a critical population size is set as an extinction threshold. We compare the real-number models with and without the Allee effect. The results show that in the presence of an Allee effect, prime-numbered life cycles are most likely to persist and to be selected under a wide range of extinction thresholds. [ABSTRACT FROM AUTHOR]

1. In 2004, Brood X of the periodical cicada ( Magicicada spp.) emerged in Delaware. Extensive suburban development and concomitant planting of exotic species has occurred since the previous emergence of Brood X in 1987. 2. Exotic species could suffer extensive damage during years of cicada emergences if they are preferred for oviposition. Alternately, a shortage of suitable plant hosts may negatively affect remaining cicada populations. 3. We determined if the periodical cicada, Magicicada septendecim, preferred to oviposit on native or exotic woody plant species. Potential hosts were divided into three groups and planted in a randomised design near a likely source of cicadas. The first group, Natives, included 15 species native to Delaware. The second group, Non-natives, included 15 exotic species that had a native congener represented in the Native group. The final group, Aliens, included 13 exotic species that did not have a native congener. 4. Based on observations of 428 plants, cicadas were more likely to oviposit on Natives or Non-natives, which did not differ from each other in this measure, than on Aliens. Non-natives had more oviposition holes per metre than Natives, which had more holes per metre than Aliens. The likelihood of stem flagging was lowest on Alien species; the percentage of the total plant that flagged was greatest for Natives. Plant morphology also influenced host preference and likelihood of flagging. 5. Taking plant morphology into consideration, we speculate that the evolutionary history between periodical cicadas and potential hosts is an important component of host preference. [ABSTRACT FROM AUTHOR]

1. Periodical cicadas occur widely in deciduous forests of eastern North America and represent the largest insect emergences in the world. Their effects on forest community dynamics, via oviposition damage and root feeding, are potentially great but not well understood. If tree species vary in their susceptibility to cicada oviposition and root colonization, then periodical cicadas may affect ecological interactions among tree species and forest composition. 2. We measured oviposition damage on 63 tree species at 52 sites in southern Indiana, U.S.A. for two broods of periodical cicadas. We compared oviposition damage among different sites, habitats, and tree species. We also measured cicada emergence rates in mature and successional forest habitats and from beneath different tree species. 3. Certain tree species received significantly more oviposition damage than others, and the most and least damaged species were consistent between the two broods. For some species, oviposition damage varied between mature and successional sites. Despite the differences in oviposition rates among species, there was no difference in emergence rates from beneath different tree species, suggesting that initial differences in cicada density among tree species are not maintained through the nymphal life cycle. 4. Cicadas oviposited more at successional sites, but emerged more in mature forest stands, suggesting that successive generations of cicadas represent a shifting mosaic between forests of different ages. As tree species consistently vary in their susceptibility to oviposition damage, periodical cicadas could alter local competitive interactions and therefore affect forest dynamics. [ABSTRACT FROM AUTHOR]

The emergence of 17-year periodical cicadas in Maryland, USA, in 2004 provided a unique opportunity to study the effect of a large, but temporally limited, resource pulse of arthropod detritus on stream ecosystem function. Cicada emergence was quantified in the forests adjacent to two small streams with different histories of riparian disturbance (Intact and Disturbed sites). We estimated the input of cicada detritus to the streams, described its retention and breakdown dynamics, and measured whole-stream respiration over the cicada flight season (May–July). Average emergence density was significantly greater at the Intact site, but average cicada detritus input rates were greater at the Disturbed site. Cicada detritus was locally retained within both streams and rapidly broke down. Daily whole-stream respiration (CR24) at both sites responded dramatically to the cicada pulse, with CR24 doubling pre-cicada measurements following the period of greatest cicada input (Intact: 12.82 → 23.78 g O2 m−2 d−1; Disturbed: 2.76 → 5.77 g O2 m−2 d−1). CR24 returned to baseline levels when cicada input decreased at the Intact site, but more than doubled again at the Disturbed site (13.14 g O2 m−2 d−1), despite a decline in cicada input rate. Differences in respiration response may be a function of differences in cicada input rates as well as differences in microbial community activity. The strong effects on stream ecosystem function exerted by a short but intense input of periodical cicada detritus may provide insights regarding the response of streams to other irregular resource pulses. [ABSTRACT FROM AUTHOR]

Insect oviposition on plants is widespread across many systems, but studies on the response of host plants to oviposition damage are lacking. Although patterns of oviposition vary spatially and temporally, ovipositing insects that exhibit outbreak characteristics may have strong effects on host plants during peak abundance. Periodical cicadas ( Magicicada spp.), in particular, may reduce the performance of host plants when they synchronously emerge in massive numbers to mate and oviposit on host plants. Here we provide the first experimental manipulation of host plant use by periodical cicadas to evaluate the impact of cicada oviposition on plant performance across a diversity of host species within an ecologically relevant setting. Using a randomized block design, we established a plantation of three native and three exotic host plant species common to the successional forests in which cicadas occur. During the emergence of Brood X in 2004, we employed a highly effective cicada exclusion treatment by netting half of the host plants within each block. We assessed multiple measures of host plant performance, including overall plant growth and the growth and reproduction of individual branches, across three growing seasons. Despite our thorough assessment of potential host plant responses to oviposition damage, cicada oviposition did not generally inhibit host plant performance. Oviposition densities on unnetted host plants were comparable to levels documented in other studies, reinforcing the ecological relevance of our results, which indicate that cicada oviposition damage did not generally reduce the performance of native or exotic host plants. [ABSTRACT FROM AUTHOR]

Abstract: The Magicicada spp. life cycles with its prime periods and highly synchronized emergence have defied reasonable scientific explanation since its discovery. During the last decade several models and explanations for this phenomenon appeared in the literature along with a great deal of discussion. Despite this considerable effort, there is no final conclusion about this long standing biological problem. Here, we construct a minimal automaton model without predation/parasitism which reproduces some of these aspects. Our results point towards competition between different strains with limited dispersal threshold as the main factor leading to the emergence of prime numbered life cycles. [Copyright &y& Elsevier]

Periodical cicadas in the genus Magicicada have an unusual life history that includes an exceptionally long life cycle and a massive, synchronized emergence. Considerable effort has been put into research aimed at understanding the evolutionary history of periodical cicadas, but surprisingly little attention has been given to their morphological evolution. Their slow flight and approachability have been described as ‘predator-foolhardy’ behaviour. We quantified flight speeds for M. cassini, M. septendecim, and Tibicen chloromera (a nonperiodical cicada species) , and interpreted them in terms of thorax musculature, body proportions and wing size and shape in relation to body size. On average, T. chloromera flew three to four times faster than did the two Magicicada species. Using empirical relationships between flight speed and body length, body mass or wing loading, we determined M. cassini and M. septendecim to be unusually slow fliers for their body size, whereas T. chloromera was not. The relatively slow flight speeds of Magicicada species could be largely accounted for by relatively small thoracic muscle masses, as indicated by thorax length × width measurements, and low wing loadings. Aspect ratio differences were contributing factors. Male Magicicada and female Tibicen were more active in mate searching than was the opposite sex, and correspondingly had relatively large aspect ratios. We interpret the morphological traits responsible for the slow flight of Magicicada species as being adaptations to searching for mates in dense aggregations around the canopy of trees, relatively unconstrained by the per-capita risk of predation. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 1–13. [ABSTRACT FROM AUTHOR]

The literature on herbivorous insects in heterogeneous habitats has addressed insect population responses to patch size, distance from source populations, habitat edges, and variation in host stem density. Studies typically conclude that insect colonists respond positively to the area of host plant patches, but there is little consensus on how insects respond to variation in host density at the patch level. Although observed variation likely results partially from differences in study species and focal habitats, deviations from expectations also may reflect the importance of unmeasured habitat parameters. In this study of colonization by cicada Magicicada cassinii (Fisher) in an experimentally fragmented old field, we simultaneously examined landscape variation in patch size, distance from the sources of colonization, and local host plant stem density (at a within-patch scale) and also considered edge effects. Per stem colonization was positively related to proximity to the population source and habitat patch size but negatively related to local host stem density. The effect of edge was nonsignificant. When coarser scale estimates of local stem density (calculated by averaging the figures for all quadrats within patches) were used in analyses, fewer significant main effects were found and sometimes interactions occurred. Our study highlights the importance of including all potential explanatory variables in analyses, with what we feel is a novel observation that the explicit consideration of fine-scale, within-patch variation in local stem density can be important to the interpretation of insect dispersal and colonization. [ABSTRACT FROM AUTHOR]

Selection against costly reproductive interactions can lead to reproductive character displacement (RCD). We use information from patterns of displacement and inferences about predisplacement character states to investigate causes of RCD in periodical cicadas. The 13-year periodical cicada Magicicada neotredecim exhibits RCD and strong reproductive isolation in sympatry with a closely related 13-year species, Magicicada tredecim. Displacement is asymmetrical, because no corresponding pattern of character displacement exists within M. tredecim. Results from playback and hybridization experiments strongly suggest that sexual interactions between members of these species were possible at initial contact. Given these patterns, we evaluate potential sources of selection for displacement. One possible source is ‘acoustical interference’, or mate-location inefficiencies caused by the presence of heterospecifics. Acoustical interference combined with the species-specificity of song pitch and preference appears to predict the observed asymmetrical pattern of RCD in Magicicada. However, acoustical interference does not appear to be a complete explanation for displacement in Magicicada, because our experiments suggest a significant potential for direct sexual interactions between these species before displacement. Another possible source of selection for displacement is hybrid failure. We evaluate the attractiveness of inferred hybrid mating signals, and we examine the viability of hybrid eggs. Neither of these shows strong evidence of hybrid inferiority. We conclude by presenting a model of hybrid failure related to life cycle differences in Magicicada. [ABSTRACT FROM AUTHOR]

Periodical cicadas in the genus Magicicada have an unusual life history that includes an exceptionally long life cycle and a massive, synchronized emergence. Distributions in woodland habitat are extremely patchy, and an unresolved problem is how the patchiness is generated and maintained. We undertook a study in Princeton, New Jersey, USA, to determine if habitat factors such as tree height, distance to the nearest neighbor, and amount of foliage influence distributions of nymphal emergences, centers of chorusing aggregations, and oviposition sites. Emerging nymphs were counted, chorus centers were identified by measuring decibel levels of their songs, and oviposition was estimated from the foliage ‘flags’ that are produced by trees in response to the damage caused by egg-laying. All three distributions were mapped on 50 trees in a human-managed area of 75 ⊗ 130 m. We were unable to identify habitat features that were associated with the distribution of emergences, except that tulip trees (Liriodendron) had significantly fewer emergences than two other genera, ash (Fraxinus) and beech (Fagus). Using multiple linear regression analysis, we found that the distribution of emergences was the best predictor of the distribution of chorus centers and oviposition sites. In an analysis of ash trees alone, tree height and spacing, in addition to cicada emergences, predicted chorus centers and oviposition incidence. Thus the distribution of the offspring generation (oviposition) is shown to be similar to the parental generation (emergence). We suggest that their stability is maintained across generations by extremely low dispersal and mutual attraction. Aggregations may be thought of as self-perpetuating, randomly distributed assemblages, initially established through the interaction of factors, including successful exploitation of under-ground resources, and avoidance of fungal disease and aboveground predation in the development of high-density mating aggregations. [ABSTRACT FROM AUTHOR]

Periodical cicadas present numerous puzzles for biologists. First, their period is fixed, with individuals emerging as adults precisely after either 13 or 17 years (depending on species). Second, even when there are multiple species of either 13- or 17-year cicadas at the same location, only one or rarely two broods (cohorts) co-occur, so that periodical cicada adults appear episodically. Third, the 13- or 17-year periods of cicadas suggest there is something important about prime numbers. Finally, single broods can dominate large areas, with geographical boundaries of broods remaining generally stable through time. While previous mathematical models have been used to investigate some of these puzzles individually, here we investigate them all simultaneously. Unlike previous models, we take an explicitly evolutionary approach. Although not enough information is known about periodical cicadas to draw firm conclusions, the theoretical arguments favor a combination of predator satiation and nymph competition as being key to the evolution of strictly fixed periods and occurrence of only one brood at most geographical locations. Despite ecological mechanisms that can select for strictly fixed periods, there seem to be no plausible ecological mechanisms that select for periods being prime numbers. This suggests that the explanation for prime-numbered periods, rather than just fixed periods, may reside in physiological or genetic mechanisms or constraints. [ABSTRACT FROM AUTHOR]

Phenotypic symmetry results from both a genetic predisposition and the influence of the developmental environment. Although most studies of mate choice and phenotypic asymmetry are couched in terms of active choice for‘good genes’, an alternative viewpoint is to consider incidental mating biases that arise from the functional effects of asymmetrical phenotypes. This paper (i) discusses the specific situations in which symmetry-based mate choice may be likely, and (ii) presents research on female mate choice and symmetry in the periodical cicada,Magicicada septendecim(L.). Male mating aggregations and lack of mating gifts or parental care make this species an ideal target for studying female choice for superior mates, and thus for a relationship between male symmetry and male mating success. [ABSTRACT FROM AUTHOR]

Many insects possess life history characteristics that make them unlikely to use the kinds of relative mate choice criteria implicit in theoretical discussions of leks; thus, many insect mating aggregations are treated differently, as 'swarms' or 'choruses.' Yet periodical cicadas (Magicicada spp.) seem strong candidates for participating in lek mating systems. We present a series of observations and experiments designed to reveal whether there are mating biases in periodical cicadas and whether any biases are most consistent with flexible ('best-of-N 'choice) or fixed (threshold choice) mating criteria. We rule out postcopulatory choice by demonstrating that most females mate once, after which they become sexually unreceptive. In our study, patterns of mating success among actively chorusing males are indistinguishable from random mating, and we uncover no consistent differences between unmated and mated males on the basis of size and song pitch, two criteria that have been associated with Magicicada mating biases in other contexts. Because our results are most consistent with a fixed-threshold choice mechanism, we suggest that Magicicada mating aggregations do not function in a manner similar to vertebrate leks even though they fulfill Bradbury's (1981) lek criteria. Instead, features of Magicicada behavior suggesting female selectivity may arise incidentally from males' and females' unequal tendencies to mate multiply, the resulting superabundance of sexually receptive males, and the high frequency at which females are courted at the onset of mating readiness. [ABSTRACT FROM AUTHOR]

Abstract: Anatomical and histological study of the Malpighian tubules in the cicada genera Tibicen and Magicicada (Cicadoidea) demonstrated that, at the nymphal stage, these organs display a glandular modification, similar to one involved in the production of the “froth” in spittlebug nymphs (Cercopoidea). Proximal parts of the tubules contain a short smooth inflated segment, which produces granules of an acid mucopolysaccharide. A more distal long nodulose segment comprises cells which display extensive rough endoplasmic reticulum and numerous secretory vacuoles, indicating the manufacture of a proteinaceous product. These cells are strongly PAS-positive, suggesting the secretory product also contains carbohydrates. The production of secretory products in the tubules ceases at the adult stage. Available observations of the behaviors of cicada nymphs suggest that the tubule secretory products mix with copious watery excretion of the gut to form the anal liquid, which is used by the nymphs to cement the walls of the burrows and clean the body. The Malpighian tubule products apparently account for the adhesive properties of the anal liquid. The regional differentiation of the tubules, details of the cell ultrastructure in each of the segments, and the major secretory products are similar to those of spittlebug nymphs, which live immersed in their excretion which is conditioned with the Malpighian tubule secretory products. The results suggest that the distinctive adaptations of juvenile Cicadoidea and Cercopoidea have a common origin. [Copyright &y& Elsevier]

Periodical cicada (Magicicada spp.) sexual pair formation takes place in dense aggregations and involves intense male-male competition for limited mating opportunities. Pair-forming behavior in these species has been poorly understood because of limited knowledge of sexual communication. We have found that sexually receptive female Magicicada flick their wings in timed response to an individual chorusing male; this previously unrecognized female response is hereafter referred to as a 'wing-flick' signal. We document the nature, timing, and species-specificity of this signal as well as its absence in both immature and mated females. We also document changes in male chorusing and searching behavior in response to wing-flick signals and male responses to the signals' visual and acoustical components. We test the hypothesis that female sensory psychology has shaped the evolution of-decim calls by favoring frequency-modulated male calls that are more readily distinguishable in an intense background chorus. Within mating aggregations, male Magicicada attempt to usurp ongoing courtships and also engage in interference competition by acoustically obscuring the calls of potential interlopers, reducing the likelihood of a female response. [ABSTRACT FROM AUTHOR]