Carolina Reigada

Educação ambiental para crianças no ambiente urbano: uma proposta de pesquisa-ação

Unitermos: educacao ambiental; pesquisa-acao-participativa; trabalho em grupo. Abstract: This research in Environmental Education involved children between six and eleven years old from a working class district - Cohab I - of a Botucatu town. The main purpose of the research was to con- tribute to the development of behaviour which involved care of the environment where they lived, giving an opportunity to obtain knowledge, values, attitudes and active interests in order to protect and make their dis- trict better. This study is based on action research that considers the participation of the people involved in knowledge production process to be fundamental. Through talks, activites and jokes, children learnt about the dis- trict, and they came to understand how they might perform an important social role of life quality improvement in environment in which they live. The children were encouraged to participate and involve adults in their concerns.

Foraging behaviour by an intraguild predator blowfly, Chrysomya albiceps (Diptera: Calliphoridae)

Optimal foraging theory assumes that predators use different prey types to maximize their rate of energetic gain. Studies focusing on prey preference are important sources of information to understand the foraging dynamics of Chrysomya albiceps. The purpose of this investigation is to determine the influence of larval starvation in C. albiceps on the predation rate of different prey blowfly species and instars under laboratory conditions. Our results suggest that C. albiceps prefers Cochliomyia macellaria larvae to Chrysomya megacephala under non-starvation and starvation conditions. Nevertheless, predators gained more weight consuming C. macellaria. This result suggests that C. albiceps profit more in consuming C. macellaria rather than C. megacephala. The foraging behaviour displayed by C. abiceps on their prey and the consequences for the blowfly community are also discussed.

Consequences of refuge for the functional response of Dermestes ater (Coleoptera: Dermestidae) to Musca domestica (Diptera: Muscidae)

It is well known that a predator has the potential to regulate a prey population only if the predator responds to increases in prey density and inflicts greater mortality rates. Predators may cause such density-dependent mortality depending on the nature of the functional and numerical responses. Yet, few studies have examined the relationship between the addition of refuges and the characteristic of functional response fits. We investigated whether addition of a refuge changed the type of functional response exhibited by Dermestes ater on Musca domestica, comparing the inherent ability of D. ater to kill houseflies in the absence and in the presence of refuge. An additional laboratory experiment was also carried out to assess handling and searching times exhibited by D. ater. Logistic regression analyses revealed a type III functional response for predator–prey interaction without refuge, and results were described by the random predator equation. The mean number of prey killed did not differ between experimental habitats, indicating that the addition of refuge did not inhibit predation. However, predators that interacted with prey without refuge spent less time searching for prey at higher densities, increasing predatory interaction. We concluded that this interaction may be weak, because data from experiments with refuge fitted poorly to models. However, the high variability and the nonsignificance of the data from the experiment with refuge show the importance of refuge for promoting spatial heterogeneity, which may prevent prey extinction.

Seasonal fecundity and body size in Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

In this study the seasonal variation of fecundity, wing and tibia size was investigated in natural populations of Chrysomya megacephala (Fabricius) aiming at determining the variations in life history of the species as a function of seasonality. A relative constant temporal trajectory was found for fecundity, wing and tibia size over twelve months. Strong positive correlations between wing size and temperature, tibia size and temperature and between wing and tibia sizes were observed. The implications of the results for population dynamics of C. megacephala were discussed.

Dispersal and Predation Behavior in Larvae of Chrysomya albiceps and Chrysomya megacephala (Diptera: Calliphoridae)

Chrysomya albiceps and Chrysomya megacephala are exotic blowfly species known by producing myiasis in humans and other animals and by transmitting pathogens mechanically. C. albiceps stand out by being a facultative predator of other dipteran larvae. In this paper we investigated the influence of larval predation on the dispersal of larvae of C. albiceps and C. megacephala single and double species for three photophases. An experimental acrylic channel graduated and covered with wood shavings was used to observe the larval dispersal. The results showed that C. albiceps attacks C. megacephala larvae during dispersal and keeps an aggregated pattern close to the release point, in single and double species, independently of the different photophases. Chrysomya megacephala single species exhibited the same pattern, but in double species this was changed to a random distribution.

The effect of hunger level on predation dynamics in the spider Nesticodes rufipes: a functional response study

It is well known that a predator has the potential to regulate a prey population only if the predator responds to increases in prey density and inflicts greater mortality rates. Predators may cause such density-dependent mortality depending on the nature of the functional and numerical responses. As spiders are usually faced with a shortage of prey, the killing behavior of the spider Nesticodes rufipes at varying densities of Musca domestica was examined here through laboratory functional response experiments where spiders were deprived of food for 5 (well-fed) or 20 days (hungry). An additional laboratory experiment was also carried out to assess handling time of spiders. The number of prey killed by spiders over 24- and 168-h periods of predator–prey interaction was recorded. Logistic regression analyses revealed the type II functional response for both well-fed and hungry spiders. We found that the lower predation of hungry spiders during the first hours of experimentation was offset later by an increase in predation (explained by estimated handling times), resulting in similarity of functional response curves for well-fed and hungry spiders. It was also observed that the higher number of prey killed by well-fed spiders over a 24-h period of spider–prey interaction probably occurred due to their greater weights than hungry spiders. We concluded that hungry spiders may be more voracious than well-fed spiders only over longer time periods, since hungry spiders may spend more time handling their first prey items than well-fed spiders.

Survival of submerged blowfly species and their parasitoids: implications for postmortem submersion interval.

Pupal survival of three blowfly species, Chrysomya albiceps, Chrysomya megacephala, and Chrysomya putoria (Diptera: Calliphoridae) and the parasitoid species Nasonia vitripennis (Hymenoptera: Pteromalidae) was studied after the pupae were experimentally submerged in water. Non-parasitized pupae at different developmental stages, 0, 24, 48, and 72 h, and parasitized pupae after 3, 8, 10, and 12 days of development were submerged for 6, 24, 48, or 72 h. Control groups for each pupal developmental stage (parasitized or not), which were not submerged, were also observed in order to compare the adult emergence rates. The survival of white pupae (0 h/age) decreased with time of submergence for all three blowfly species, showing the lowest rates compared with other experimental pupa groups. For the three blowfly species, non-parasitized pupae at 24 and 48 h of age showed survival rates above 60%. However, for pupae at 72 h of age, the survival rates decreased with increased underwater time, with less than 30% survival after 72 h in C. putoria and C. albiceps. The survival of parasitoids inside blowfly pupae that were submerged during their larval stage (3 days/age) decreased with the increase of submergence time. After the parasitoids reached the pre-pupal life stage, the survival was higher for all underwater periods. These observations can be useful in investigations of the decomposition of partially submerged bodies, or in cases of pupae found adhering to decaying flesh, hair, or clothes of corpses that were submerged after the larvae had developed and pupated.

Direct and indirect top-down effects of previous contact with an enemy on the feeding behavior of blowfly larvae

We investigated the addition of a trophic level to a simple food web. Direct and indirect effects caused by the presence of a new species in the food web were quantified by estimating survival and consumption rates on the basal resource. We focused on a blowfly intraguild prey–predator system with various ecological interactions taking place during the larval period. The experiments were designed to set Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) as the intraguild prey and Chrysomya albiceps (Wiedemann) as the intraguild predator and/or cannibal. The generalist pupal parasitoid Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) was introduced into the system during a non‐susceptible life stage of the interacting blowfly species. The cascading parasitoid effects induced behavioral changes in the blowfly larvae, increasing the impact of intraguild predation and cannibalism on blowfly survival. The results suggest that blowfly larvae can change their feeding behavior in response to the presence of a parasitoid.

The bizarre male of Spalangia dozieri (Hymenoptera: Pteromalidae): adaptations for male phoresy or the result of sexual selection?

Abstract Spalangia dozieri Burks is newly recorded as a gregarious parasitoid in the puparia of Chrysomya albiceps (Wiedemann), C. putoria (Wiedemann), Lucilia eximia (Wiedemann), and L. sericata (Meigen) (Diptera: Calliphoridae), and represents the first report of gregariousness in Spalangia Latreille. The previously unknown males of S. dozieri are described and compared with females. Males have highly modified legs and several other sexually dimorphic features that differ from those of other Spalangia species. Most of the unusual features are hypothesized to be adaptations for grasping and holding and it is suggested that males either are phoretic on adults of their dipteran hosts or, possibly, that males exhibit aggressive or other atypical behaviour toward siblings that is correlated with being gregarious. Barbados, Brazil, Dominica, St. Lucia, St. Vincent, and Trinidad are recorded as new country distribution records for S. dozieri.

Effect of Psychoactive Drugs on Demographic Parameters of the Blow Fly Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae)

Knowledge of the factors influencing the ecology of blow flies, especially the dynamic population equilibrium, is essential in forensic entomology. However, lack of knowledge of the action of psychoactive drugs on the population dynamics of these flies may affect the inferences that experts must make in medico-legal reports. This study evaluated the effects of amphetamine and phenobarbital on the population dynamics of Chrysomya albiceps (Wiedemann), by combining laboratory experimentation and mathematical modelling. Only amphetamine and its control, methanol, influenced the qualitative dynamic behaviour of Chrysomya albiceps, stabilising chaotic populations. The results are discussed in an ecological and forensic context.