Flight and dispersal of periodical cicadas

Summary Periodical cicadas (Magicicada spp.) rarely flew distances greater than 50 m across an open field or along a forest edge. Most cicadas caught after flying 50 m or more were females and all of these females had mated. Flights were most common when adults were 2 to 3 weeks old. Among insects in general, most dispersing individuals are barely post-teneral or extremely young. Cicadas are discussed as an exception to this generality. Both sexes of cicadas are attracted by the male song to chorusing centers for mating (Alexander and Moore 1958). Trees which were chorusing centers had more eggnests than those which were not, suggesting a lack of postmating dispersal from the chorusing trees.     

Marriage and mortality: a life table analysis

This paper examines the effects of age at marriage and differential mortality of males and females on the incidence of widowhood between the sexes. Abridged life tables constructed from marital status and death registration data of a rural area of Bangladesh for the period 1974-79 were used. The difference in life expectancy between males and females varies from 0.4 to 2.2 years at the ages 0 to 65 years and over. The mortality differentials show that the probabilities of a male or a female surviving the other spouse would be approximately the same, were there no other influence. But the incidence of widows is about ten times that of widowers. Other relevant factors, under a given regime of mortality, are age at marriage and age difference between husband and wife.     

Effects of local density on fecundity and mating speed for periodical cicadas

Summary This paper catalogues several different dichotomies that have all been termed r- and K-selection. The status of the concept of r- and K-selection is discussed and a more restricted usage of the terms is recommended.     

Spatial variability in oviposition damage by periodical cicadas in a fragmented landscape

Effects of the periodical cicada (Magicicada spp.) on forest dynamics are poorly documented. A 1998 emergence of M. cassini in eastern Kansas led to colonization of a fragmented experimental landscape undergoing secondary succession. We hypothesized that per-tree rates of oviposition damage by cicadas would reflect: (1) distance from the source of the emergence, (2) patch size, and (3) local tree density. Ovipositing females displayed clear preferences for host species and damage incidence showed predictable spatial patterns. Two species (smooth sumac, Rhus glabra, and eastern red cedar, Juniperus virginiana) were rarely attacked, whereas others (rough-leaved dogwood, Cornus drummondii; slippery elm, Ulmus rubra; box elder, Acer negundo, and honey locust, Gleditsia triacanthos) were strongly attacked. The dominant early successional tree, dogwood, received on average the most attacks. As predicted, attacks per stem declined strongly with distance from the emergence source, and with local stem density (a "dilution" effect). Contrary to expectations, there were more attacks per stem on larger patches. Because ovipositing cicadas cut damaging slits in host tree branches, potentially affecting tree growth rate, competitive ability, and capacity to reproduce, cicada damage could potentially influence spatial variation in secondary succession.     

The multiple decrement life table: a unifying framework for cause-of-death analysis in ecology

Summary The multiple decrement life table is used widely in the human actuarial literature and provides statistical expressions for mortality in three different forms: i) the life table from all causes-of-death combined; ii) the life table disaggregated into selected cause-of-death categories; and iii) the life table with particular causes and combinations of causes eliminated. The purpose of this paper is to introduce the multiple decrement life table to the ecological literature by applying the methods to published death-by-cause information on Rhagoletis pomonella. Interrelations between the current approach and conventional tools used in basic and applied ecology are discussed including the conventional life table, Key Factor Analysis and Abbott's Correction used in toxicological bioassay.     

A general theory of life table construction and a precise abridged life table method

"In this paper we lay the foundation of life table construction by unifying the existing life table methods. We also present a new method of constructing current (period) abridged life tables.... The development includes (1) a careful formulation and computation of age-specific death rates, (2) derivation of a new set of formulas for computing the survivorship function from the observed age-specific death rates and populations, (3) estimation of the main life table functions by spline interpolation, integration and differentiation, and (4) use of a quadratic and a Gompertz function to close the life table.... The method is illustrated with construction of abridged life tables using Canadian data."     

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.     

Sexual dimorphism of motorneurons: Timbal muscle innervation in male periodical cicadas and homologous structures in females

Summary Treatment of cultured goldfish xanthophores by hormone (ACTH) or c-AMP induces not only pigment dispersion, but subsequent outgrowth of processes, and pigment translocation into these processes. These latter effects are shown to proceed as follows: First the edge of the cytoplasmic lamellae takes on a scalloped contour with numerous protrusions. These presumably serve as nucleation centers where short microfilament bundles are assembled, Later, the microfilament bundles elongate (grow), often resulting in an extension of the protrusions to become filopodia while the proximal end of the microfilaments penetrates into the thicker portion of the cellular process which now houses the pigment, i.e., the carotenoid droplets. Carotenoid droplets appear to migrate along the microfilament bundles, or cytoplasmic channels associated with them, into the filopodia. Finally, some of the filopodia become broader, thicker and laden with carotenoid droplets and are then recognized by light microscopy as pigmented cellular processes. The microfilaments have been shown to be actin filaments by their thickness, the size of their subunits, and decoration by heavy meromyosin. Evidence is presented which suggests that the growth of these actin filaments may come about by recruitment from short F-actin strands found in random orientation in adjacent areas.     

Competing risk analysis for life table data with known observation times

"Several models have been proposed for the analysis of cohort mortality in the presence of competing risks.... This paper describes a maximum likelihood approach to the analysis of follow up data in life table format for the case of two competing risks--a specific cause and its competing complement. The model developed uses a robust survivorship assumption--the piecewise exponential--and takes into account information on time to death and time to withdrawal." (summary in GER)     

Comparison of exclusion and imidacloprid for reduction of oviposition damage to young trees by periodical cicadas (Hemiptera: Cicadidae)

Insecticides are traditionally used to control periodical cicadas (Homoptera: Cicadidae) and to reduce associated injury caused by oviposition. However, research has shown that conventional insecticides have low or variable season-long efficacy in reducing injury caused by cicadas. New systemic neonicotinoid insecticides provide excellent levels of control against a variety of sucking insects. We compared the efficacy of a neonicotinoid insecticide, imidacloprid, and a nonchemical control measure, netting, to reduce cicada injury. Netted trees sustained very little injury, whereas unprotected trees were heavily damaged. Fewer eggnests, scars, and flags were observed on trees treated with imidacloprid compared with unprotected trees; however, the hatching of cicada eggs was unaffected by imidacloprid.     

Model life table for captive chimpanzees

Mortality statistics from three captive populations of chimpanzees (Pan troglodytes) were combined to generate standard model life tables for each sex in this species. The model is compared to an estimate of survivorship of a group of wild animals, and is applied to an incomplete data set to illustrate how the model may be used to extend estimates of mortality statistics to missing older ages. © 1995 Wiley-Liss, Inc.     

Developmental rate estimation and life table analysis for Halyomorpha halys (Hemiptera: Pentatomidae)

Egg and nymphal development were studied under constant temperatures for the newly introduced pest species, Halyomorpha halys (St?l) (Hemiptera: Pentatomidae). Development was assessed at seven constant temperatures (15-35 degrees C). Development to adult was completed at temperatures between 17 and 33 degrees C, with egg hatch also occurring at 15 degrees C. The relationship between temperature and developmental rate was evaluated using three developmental models. Of the models evaluated, the Briere-1 model was the best fit for the empirical data of egg and total development and for providing accurate values for the temperature threshold. Application of the linear degree-day model estimated 537.63 DD are needed for total development (egg to imaginal ecdysis). An additional 147.65 DD are needed for the preoviposition period of the female. Reproductive parameters were evaluated at 25 degrees C and indicate a median number of 28 eggs per egg mass. Oviposition occurred at 4.32-d intervals, and a female can continue to oviposit throughout its lifespan. H. halys is univoltine in New Jersey and Pennsylvania, but if it spreads to warmer climates in the United States, it could have multiple generations per year.     

The priming of periodical cicada life cycles

Periodical cicadas in the genus Magicicada have unusually long life cycles for insects, with periodicities of either 13 or 17 years. Biologists have explained the evolution of these prime number period lengths in terms of resource limitation, enemy avoidance, hybridization and climate change. Here, I question two aspects of these explanations: that the origin of the life cycles was associated with Pleistocene ice age events, and that they evolved from shorter life cycles through the lengthening of nymphal stages in annual increments. Instead, I suggest that these life cycles evolved earlier than the Pleistocene and involved an abrupt transition from a nine-year to a 13-year life cycle, driven, in part, by interspecific competition.     

In situ life table of a subtropical copepod

• 1 A life table of a subtropical population of Mesocyclops edax(Copepoda: Cyclopoida) was constructed from a cohort of individuals reared in enclosures in a small, eutrophic lake.
• 2 The lake population was sampled concurrently to determine age structure, per capita birth, death and growth rates, body size and clutch size.
• 3 Maturation times of enclosed males and females were 9.3 and 11.4 days, respectively. The population growth rate. r. was estimated to be 0.18 females day^-1 for the enclosed population, but approximated zero on most dates in the lake population. Mortality was low in the enclosures which excluded predators and high in the field population exposed to planktivorous fish and Chaoborus.
• 4 The means and variances of several fitness traits are related to the specific environment. The enclosure approach promises to be a useful tool in the study of zooplankton life history variation.

     

Diapause and prolonged development in the embryo and their ecological significance in two cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata

The seasonal timing mechanism of egg hatching was examined in two cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata, with different but overlapping geographical distributions. These species lay eggs in summer, and nymphs hatch in the summer of the following year after egg durations of 10-12 months. When eggs were maintained at 25 °C from oviposition, both the species entered embryonic diapause within 60 days irrespective of photoperiod, but at different developmental stages between the two species. The optimal temperature for diapause development was approximately 15 °C in both the species. The development rate for postdiapause morphogenesis increased linearly with temperature in the range of 20-27.5 °C in C. facialis, and of 15-25 °C in G. nigrofuscata. The lower development threshold and the sum of effective temperatures were computed as 14.3 °C and 715.3 day-degrees in C. facialis and 12.1 °C and 566.6 day-degrees in G. nigrofuscata, respectively. The hatching dates predicted by these large thermal constants accorded with the hatching dates observed in the field, i.e., late June and mid-July in G. nigrofuscata and C. facialis, respectively. Therefore, the high thermal requirements for postdiapause development compel the cicadas to hatch in summer.     

Resource pulses of dead periodical cicadas increase the growth of American bellflower rosettes under competitive and non-competitive conditions

This experiment investigates how pulsed nutrient resources interact with intraspecific competition to influence biomass production and nutrient use efficiency in the American bellflower (Campanulastrum americanum). The competitive environment of these plants was manipulated by growing plants alone or with neighboring conspecifics, and the occurrence of pulsed nutrient resources was manipulated through the addition of 17-year periodical cicada (Magicicada septendecim) carcasses in order to simulate naturally occurring pulsed resources in this system. The addition of cicada carcasses increased mean plant biomass by 61 % compared to non-supplemented plants, while competition decreased mean plant biomass by 44 % compared to plants grown without competition; these effects were additive. In comparison, nutrient use efficiency decreased in fertilized plants (cicada-supplemented plants showed 20 % greater foliage nitrogen concentrations compared to non-supplemented plants), but was not significantly affected by the plant’s competitive environment. In addition, cicada supplementation did not significantly increase the biomass asymmetry in competing pairs of plants. These results suggest that these plants increased their total nutrient uptake at a timescale commensurate with the pulsed increase in nutrient availability due to cicada carcass decomposition.