Effect of heavy-equipment aided environmental nebulization on Aedes aegypti vectors of Dengue, Zika and Chikungunya in São Paulo, Brazil.

The control of dengue constitutes a great challenge for public health; however, the methods normally used have shown themselves to be insufficient to keep the indices of infestation of Aedes aegypti under control. Recently, beyond the large number of cases and deaths associated with dengue, new risks have arisen such as those represented by chikungunya fever and Zika. In the light of the great significance of these problems within the public health context, two areas in a municipality in the interior of the State of São Paulo, Brazil were selected in 2014. One of them, Bairro Cidade Nova, was submitted to the conventional method of nebulization with portable equipment, and the other, Bairro Jardim Europa, received the application of the insecticide by means of heavy-equipment coupled to the vehicle. During the project, 1355 mosquito eggs were collected, 1105 of them in Bairro Cidade Nova and 205 in Bairro Jardim Europa. After the applications with heavy-equipment in the months of March and April, the number of cases of the disease reported in the month of April for Bairro Jardim Europa was less than half that of Bairro Cidade Nova, which had received the conventional treatment. The nebulization with the heavy-equipment may constitute a viable and effective strategy for achieving better results in the control of Ae. aegypti.

Synanthropy of Sarcophagidae (Diptera) in southeastern Brazil.

Sarcophagidae (Diptera) are potential vectors of several pathogens. They are also very important in forensic entomology, providing basic information on the circumstances of death. The objective of this study was to determine the synanthropic index of adult Sarcophagidae collected in Rio Claro, state of São Paulo, southeastern Brazil. Sampling occurred between September 2009 and August 2010. Traps baited with sardines, beef liver, or minced meat were set for five consecutive days per month in three distinct ecological areas representing urban, rural, and forest environments. A total of 440 specimens of sarcophagids were collected. The most abundant species was Peckia (Sarcodexia) lambens (Wiedemann), followed by Oxysarcodexia thornax (Walker), Peckia (Euboettcheria) collusor (Curran & Walley), Peckia (Euboettcheria) sp., and Peckia (Pattonella) intermutans (Walker). The only species with positive synanthropic index values were O. thornax and P. (S.) lambens, which demonstrated a greater preference for inhabited areas. Peckia (Euboettcheria) florencioi (Prado & Fonseca), P. (P.) intermutans, and Peckia (Euboettcheria) australis (Townsend) were only found in the forested area, which demonstrates their importance in forensic entomology because of their preference for a particular type of environment. The greatest number of sarcophagids was found in the forest environment; however, only the forest and rural areas were significantly different in Sarcophagidae abundance.

Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) Oviposition Behavior in Previous Oviposition Situation.

Blowflies use their sense of smell to locate oviposition substrates and their vision to direct and assist in landing decision. Blowflies' ovipositions are usually aggregated. Chrysomya megacephala (Fabricius) females, for example, prefer to lay eggs on substrates containing fresh eggs of the same species. However, it is possible that females would be capable of evaluating the substrate, reducing the size of egg cluster in sites with a high amount of eggs or larvae, or finding another site for laying their eggs, preventing the progeny from facing high competition for space and food. The present study aimed to investigate whether females of C. megacephala could distinguish and preferentially select previously infested substrates and whether females would lay their eggs attached or separate from eggs previously laid on the substrate. Behavioral measures were conducted inside cages under laboratory conditions in free-choice tests. Data analysis confirmed that C. megacephala females are able to distinguish the presence of cospecific eggs in the substrate and preferentially select previously infested substrates for egg laying, depositing their eggs separate from pre-existing large egg masses.

Sex ratio and dynamic behavior in populations of the exotic blowfly Chrysomya albiceps (Diptera, Calliphoridae).

Sex ratio is an essential component of life history to be considered in population growth. Chrysomya albiceps is a blowfly species with a naturally biased sex ratio. In this study, we evaluated the impact of changes in sex ratio on the dynamic behavior of C. albiceps using a density-dependent mathematical model that incorporated demographic parameters such as survival and fecundity. These parameters were obtained by exponential regression, with survival and fecundity being estimated experimentally as a function of larval density. Bifurcation diagram of the results indicated the evolution of stable equilibrium points as a function of sex ratio. A continually increasing sex ratio yielded a hierarchy of bifurcating stable equilibrium points that evolved into a chaotic regime. The demographic parameters obtained by exponential regression were also changed to maximum and minimum values in order to analyze their influence on dynamic behavior with sex ratio being considered as an independent variable. Bifurcations with periodicity windows between chaos regimes were also found.

Sex ratio and dynamic behavior in populations of the exotic blowfly Chrysomya albiceps (Diptera, Calliphoridae)

Sex ratio is an essential component of life history to be considered in population growth. Chrysomya albiceps is a blowfly species with a naturally biased sex ratio. In this study, we evaluated the impact of changes in sex ratio on the dynamic behavior of C. albiceps using a density-dependent mathematical model that incorporated demographic parameters such as survival and fecundity. These parameters were obtained by exponential regression, with survival and fecundity being estimated experimentally as a function of larval density. Bifurcation diagram of the results indicated the evolution of stable equilibrium points as a function of sex ratio. A continually increasing sex ratio yielded a hierarchy of bifurcating stable equilibrium points that evolved into a chaotic regime. The demographic parameters obtained by exponential regression were also changed to maximum and minimum values in order to analyze their influence on dynamic behavior with sex ratio being considered as an independent variable. Bifurcations with periodicity windows between chaos regimes were also found.

A razão sexual é um componente essencial da biologia de organismos a ser considerado em crescimento populacional. Chrysomya albiceps é uma espécie de mosca varejeira que exibe um desvio na razão sexual em relação à proporção 1:1. Neste estudo avaliamos o impacto de alterações na razão sexual sobre o comportamento dinâmico de C. albiceps utilizando um modelo matemático dependente da densidade que incorpora parâmetros demográficos como sobrevivência e fecundidade. Os parâmetros foram obtidos por regressão exponencial, com sobrevivência e fecundidade sendo estimadas experimentalmente em função da densidade larval. O diagrama de bifurcação gerado pelos resultados indicou a evolução de pontos de equilíbrio estável em função da razão sexual. A sucessão contínua dos valores da razão sexual resultou em uma hierarquia de pontos de equilíbrio estável produzida por bifurcações, resultando em regime caótico. Os parâmetros demográficos obtidos por regressão exponencial foram também mudados para valores máximos e mínimos, a fim de analisar a influência deles sobre o comportamento dinâmico da espécie, tendo a razão sexual como variável independente. Bifurcações com janelas de periodicidade intercaladas com o regime caótico também foram encontradas.

Spatio-temporal dynamics and transition from asymptotic equilibrium to bounded oscillations in Chrysomya albiceps (Diptera, Calliphoridae).

The sensitivity of parameters that govern the stability of population size in Chrysomya albiceps and describe its spatial dynamics was evaluated in this study. The dynamics was modeled using a density-dependent model of population growth. Our simulations show that variation in fecundity and mainly in survival has marked effect on the dynamics and indicates the possibility of transitions from one-point equilibrium to bounded oscillations. C. albiceps exhibits a two-point limit cycle, but the introduction of diffusive dispersal induces an evident qualitative shift from two-point limit cycle to a one fixed-point dynamics. Population dynamics of C. albiceps is here compared to dynamics of Cochliomyia macellaria, C. megacephala and C. putoria.

[Larval competition in Chrysomya megacephala (F.) (Diptera: Calliphoridae): effects of different levels of larval aggregation on estimates of weight, fecundity and reproductive investment]. / Competição larval em Chrysomya megacephala (F.) (Diptera: Calliphoridae): efeitos de diferentes niveis de agregação larval sobre estimativas de peso, fecundidade e investimento reprodutivo.

In insects that utilize patchy and ephemeral resources for feeding and egg laying, the outcome of larval competition for food resources depends on the amount of resources and the spatial distribution of immatures among patches of food. In the present study, the results of larval competition for food in Chrysomya megacephala, in traits such as female weight, fecundity and reproductive investment, were different in situations where the level of larval aggregation (proportion of competitors per amount of food) was the same, but with densities of competitors and amounts of food proportionally different. These results are indicative that the larval competition may depend both on the larval density and the amount of food, in different situations with the same proportion of larvae per gram of food.

Competiçäo larval em Chrysomya megacephala (F.) (Diptera: Calliphoridae): efeitos de diferentes níveis de agregaçäo larval sobre estimativas de peso, fecundidade e investimento reprodutivo / Larval competition in Chrysomya megacephala (F.) (Diptera: Calliphoridae): effects of different levels of larval aggregation on estimates of weight, fecundity and reproductive investment

Em insetos que se utilizam de substratos discretos e efêmeros para a alimentação e postura de ovos, o resultados da competição larval por alimento depende da quantidade de recursos e da distribuição espacial dos imaturos nos substratos alimentares. No presente estudo, os resultados da competição larval por alimento em Chrysomya megacephala, em caracteres como peso de fêmeas, fecundidade e investimento reprodutivo, foram diferentes em situações em que o nível de agregação larval (proporção de competidores por qualtidade de alimento) é o mesmo, mas com densidades de competidores e quantidades de alimento proporcionalmente diferentes. Esses resultados indicam que a competição larval pode depender tanto da densidade larval como da quantidade de alimento, em situações diferentes com a mesma proporção de larvas por grama de alimento.

Diffusion model applied to postfeeding larval dispersal blowflies (Diptera: Calliphoridae)

This paper presents a diffusion model of larval dispersal especifically designed to account for particular aspects of postfeeding larval dispersal from the food source in organisms such as blowflies. In these organisms the dispersal of immatures includes two groups of individuals, those that are actively migrating and those that initiated the pupation process. The classical diffusion equation in one dimension was modified to incorporate a function which describes the burying of larvae to become pupae. The analytical solution of this equation predicts oscillatory and monotonic dispersal behaviors, which are observed in experimental populations of blowfly species.

Diffusion model applied to postfeeding larval dispersal in blowflies (Diptera:Calliphoridae).

This paper presents a diffusion model of larval dispersal specifically designed to account for particular aspects of postfeeding larval dispersal from the food source in organisms such as blowflies. In these organisms the dispersal of immatures includes two groups of individuals, those that are actively migrating and those that have initiated the pupation process. The classical diffusion equation in one dimension was modified to incorporate a function which describes the burying of larvae to become pupae. The analytical solution of this equation predicts oscillatory and monotonic dispersal behaviors, which are observed in experimental populations of blowfly species.

[Implications of spatial aggregation of parasites for the population dynamics in host-parasite interaction]. / Implicações da agregação espacial de parasitas para a dinâmica populacional na interação hospedeiro-parasita.

Some aspects of the widely observed over-dispersed pattern of the distribution of parasites within the host population are examined. It has been established in the parasitological literature that most hosts usually harbour few parasites, while only few hosts harbour a large proportion of the parasite population. Factors that may influence the pattern of distribution of parasites, the relation between the level of parasite aggregation and the prevalence of infection, and changes in this level of aggregation as a function of host age are analysed. Factors which determine the diversity of species in parasite communities are presented, and aspects of exploitative and interference competition among parasites and their relations with biological control procedures are also considered. Attention is also focused on the regulatory and destabilizing processes influencing the dynamic behaviour of host-parasite population interactions.

Theoretical dynamics of experimental populations of introduced and native blowflies (Diptera:Calliphoridae).

Equilibrium dynamics in experimental populations of Chrysomya megacephala (F.) and C. putoria (Wiedemann), which have recently invaded the Americas, and the native species Cochliomyia macellaria (F.), were investigated using nonlinear difference equations. A theoretical analysis of the mathematical model using bifurcation theory established the combination of demographic parameters responsible for producing shifts in blowfly population dynamics from stable equilibria to bounded cycles and aperiodic behavior. Mathematical modeling shows that the populations of the 2 introduced Chrysomya species will form stable oscillations with numbers fluctuating 3-4 times in successive generations. However, in the native species C. macellaria, the dynamics is characterized by damping oscillations in population size, leading to a stable population level.

Theoretical estimates of consumable food and probability of acquiring food in larvae of Chrysomya putoria (Diptera: Calliphoridae)

An indirect estimate of consumable food and probability of acquiring food in a blowfly species, Chrysomya putoria, is presented. This alternative procedure combines three distinct models to estimate consumable food in the context of the exploitative competition experienced by immature individuals in blowfly populations. The relevant parameters are derived from data for pupal weight and survival and estimates of density-independent larval mortality in twenty different larval densities. As part of this procedure, the probability of acquiring food per unit of time and the time taken to exhaust the food supply are also calculated. The procedure employed here may be valuable for estimations in insects whose immature stages develop inside the food substrate, where it is difficult to partial out confounding effects such as separation of faeces. This procedure also has the advantage of taking into account the population dynamics of immatures living under crowded conditions, which are particularly characteristic of blowflies and other insects as well.

Theoretical estimates of consumable food and probability of acquiring food in larvae of Chrysomya putoria (Diptera: Calliphoridae).

An indirect estimate of consumable food and probability of acquiring food in a blowfly species, Chrysomya putoria, is presented. This alternative procedure combines three distinct models to estimate consumable food in the context of the exploitative competition experienced by immature individuals in blowfly populations. The relevant parameters are derived from data for pupal weight and survival and estimates of density-independent larval mortality in twenty different larval densities. As part of this procedure, the probability of acquiring food per unit of time and the time taken to exhaust the food supply are also calculated. The procedure employed here may be valuable for estimations in insects whose immature stages develop inside the food substrate, where it is difficult to partial out confounding effects such as separation of faeces. This procedure also has the advantage of taking into account the population dynamics of immatures living under crowded conditions, which are particularly characteristic of blowflies and other insects as well.

Dynamics of a mathematical model of Chrysomya megacephala (Diptera: Calliphoridae).

The laboratory population dynamics of Chrysomya megacephala (F.) was explored with a mathematical model of density-dependent growth. Fecundity and survival decreased significantly as a function of larval density. Parameters in the exponential regressions fitted to the fecundity and survival data were incorporated into a finite-difference equation that incorporates the delayed effect of larval density on fecundity and survival of adults. The theoretical population model of C. megacephala showed cyclic behavior with a stable limit cycle of two points for adults and immatures.