Dynamics of experimental populations of native and introduced blowflies (Diptera: Calliphoridae): mathematical modelling and the transition from asymptotic equilibrium to bounded oscillations

The equilibrium dynamics of native and introduced blowflies is modelled using a density-dependent model of population growth that takes into account important features of the life-history in these flies. A theoretical analysis indicates that the product of maximum fecundity and survival is the primary determinant of the dynamics. Cochliomyia macellaria, a blowfly native to the Americas and the introduced Chrysomya megacephala and Chrysomya putoria, differ in their dynamics in that the first species shows a damping oscillatory behavior leading to a one-point equilibrium, whereas in the last two species population numbers show a two-point limit cycle. Simulations showed that variation in fecundity has a marked effect on the dynamics and indicates the possibility of transitions from one-point equilibrium to bounded oscillations and aperiodic behavior. Variation in survival has much less influence on the dynamics.

Distinction among the puparia of three blowfly species (Diptera: Calliphoridae) frequently found on unburied corpses

Calliphorid larvae are important in the decomposition of carrion. Since these larvae are present in the primary stages of succession on carcasses, they may be important indicators of death time and the movement of corpses in homicide investigations. In this study we examined the morphological differences among puparia of Chrysomya megacephala, C. putoria and Cochliomyia macellaria. Puparia of the three species (N=30, each) were obtained from the F2 generation bred in culture medium at 25° C, and 60% relative humidity on a 12 h photoperiod. The interspecific differences found were related to the conspicuousness of six tubercles located in the region near the posterior spiracles and to the distance between the two peritrema involving the spiracles. The latter were (mean ± SD) 15.2 ± 3.1 mum for C. megacephala, 18.8 ± 2.8 mum for C. putoria and 16.5 ± 3.5 mum for C. macellaria. The results of the present study may be useful in forensic entomology.

Flies (Calliphoridae, Muscidae) and Beetles (Silphidae) from Human Cadavers in Cali, Colombia

Adult specimens of Cochliomyia macellaria, Chrysomya megacephala, Ch. rufifacies, Lucilia sp. (Calliphoridae), Musca domestica (Muscidae), Oxelytrum discicolle (Silphidae) and Sarcophagidae were recovered from 12 human cadavers in Cali, Valle, Colombia. Information regarding these findings is presented.

Análise faunística de Calliphoridae (Diptera) da Reserva Biológica do Tinguá, Nova Iguaçu, Rio de Janeiro

O presente estudo investiga a fauna de califorídeos na Reserva Biológica do Tinguá usando como meios os índices faunísticos. Realizaram-se coletas mensais com armadilhas contendo sardinha expostas por 48 horas, nos pontos: A- borda da mata; B- 1000 metros para interior da mata; C- 500 metros para interior da mata. Objetivou-se estudar a entomofauna califorídica em ambiente florestal através de índices faunísticos. Foram coletadas 26 espécies de califorídeos ao longo do experimento. Definiram-se espécies Singletons, Doubletons, Uniques e Duplicates, intermediárias e comuns; calcularam-se riqueza e projeção da riqueza (estimadores Chao 1 e 2, Jackknife 1 e 2, Ace, Ice e Bootstrap); diversidade (Índice Shannon-Wiener); equidade (Índice Pielou) e similaridade dos pontos (quociente Sorensen e porcentagem de similaridade Southwood). Os pontos A e B mostraram o mesmo número de espécies de califorídeos (23), maior que C (16), diferindo apenas nas espécies raras, intermediárias e comuns. Em A foi registrado grande número de espécies consideradas intermediárias. Em B o número de espécies raras, intermediárias e comuns foi similar. Em C, o número de espécies raras foi menor que de intermediárias e comuns. Jackknife 2 no ponto B gerou a maior riqueza, indicando possibilidade de serem coletadas mais cinco espécies na reserva além das coletadas neste estudo, e em A e C mais três espécies. Ace e Bootstrap apresentaram-se seguros para estimativa de riqueza de Calliphoridae. A diversidade foi maior em B. A equidade foi semelhante nos pontos. B e C foram mais semelhantes em relação às espécies (dendograma): Laneela nigripes e Mesembrinella bellardiana, principais destes dois pontos aparecem agrupadas; Chrysomya albiceps, Chrysomya megacephala e Hemilucilia semidiaphana, principais espécies em A aparecem unidas.

Nutritional ecology of blowflies (Diptera, Calliphoridae): estimates of critical larval weight for pupation on two different

Under natural environmental conditions, blowflies utilize discrete and ephemeral feeding resources such as decaying carcasses. Competition for food on such feeding substrates is usually very severe, and only the individuals that are capable of attaining the critical larval weight for pupation will be able to survive. This critical weight is hitherto unknown for several blowfly species; therefore, the current work is aimed at obtaining such a critical value for four blowfly species of the genera Chrysomya and Lucilia, deploying two types of feeding substrate, namely, artificial diet and macerated bovine meat. On the whole, the critical weights ranged from 30 to 35 mg. The lowest larval weight which permitted pupation was 30.0 mg for Chrysomya megacephala reared on macerated bovine meat. This species was also the best adapted to pupation at low larval weights in relation to the maximum larval weight for males. Regarding the pupation of females, the best-adapted individual was a C. albiceps specimen exhibiting a critical weight that was equal to 39.20 % of the maximum value obtained. Concerning all the species and diet types, the female individuals exhibited the lowest critical weights that produced viable pupae, probably representing an evolutionary strategy that favoured the survival of females, responsible for the egg formation, contributing to the establishment of future generations. Regarding the loss (in percentage) of adult biomass in relation to the third instar larvae, the females of C. megacephala lost less weight than males in both feeding substrates. On the other hand, such a loss of weight occurred in males of C. albiceps and L. cuprina.

Nim (Azadirachta indica): uma alternativa no controle de moscas na pecuária

As moscas Lucilia cuprina, Chrysomya megacephala, Cochliomyia hominivorax e Musca domestica, estão entre as mais importantes pragas da pecuária causando miíases e como portadoras de microrganismos patogênicos. O propósito deste estudo foi testar a eficácia de várias concentrações do óleo de nim sobre pupas das moscas mencionadas em condições de laboratório e de campo. A redução da emergência das moscas das pupas tratadas com 0,6 por cento de óleo de nim foi de 95,6 por cento em condições de laboratório e 94,5 por cento quando aplicado ao solo onde descansam os animais durante a noite. A aplicação do óleo de nim a 0,6% no solo é uma alternativa viável para controle das pupas de L. cuprina, C. megacephala, C. hominivorax e M. domestica.

Abundance and seasonality of Diptera (Insecta) in a poultry house in the northeast region of the state of Sao Paulo, Brazil

Modem production systems accommodate broody hens in high densities, leading to the accumulation of excrement under the cages. This substrate is excellent for the development of sinantropic flies. Thus, the accomplishment of surveys in these places becomes essential, in order to plan better strategies of control. The present work aimed at studying the entornofauna and the seasonality of the species of dipterous present in the Crisdan poultry house located in the Municipality of Sao Joao da Boa Vista, the State of Sao Paulo, Brazil. In the period of January of 2001 to December of 2002, 1,012,595 flies were captured using the ""jug-trap"". The species were identified: Drosophi-la repleta (Wollaston, 1858), Musca domestica (Linnaeus, 1758), Ophyra spp., Hennetria illucens (Linnaeus, 1758), Fannia canicularis (Linnaeus, 1761), Chrysomya megacephala (Fabricius, 1794), and Sepsidae. More frequently D. repleta and M. domestica had added 99.47% of the dipterous. Increased rainfall and the collection months influenced the sampling of dipterous (P < 0.05). Drosophila repleta was the most abundant species, representing 91% of all captured flies. However, this diptera did not develop at the surveyed site since immatures were not captured therein.

Recording from Two Neurons: Second-Order Stimulus Reconstruction from Spike Trains and Population Coding

We study the reconstruction of visual stimuli from spike trains, representing the reconstructed stimulus by a Volterra series up to second order. We illustrate this procedure in a prominent example of spiking neurons, recording simultaneously from the two H1 neurons located in the lobula plate of the fly Chrysomya megacephala. The fly views two types of stimuli, corresponding to rotational and translational displacements. Second-order reconstructions require the manipulation of potentially very large matrices, which obstructs the use of this approach when there are many neurons. We avoid the computation and inversion of these matrices using a convenient set of basis functions to expand our variables in. This requires approximating the spike train four-point functions by combinations of two-point functions similar to relations, which would be true for gaussian stochastic processes. In our test case, this approximation does not reduce the quality of the reconstruction. The overall contribution to stimulus reconstruction of the second-order kernels, measured by the mean squared error, is only about 5% of the first-order contribution. Yet at specific stimulus-dependent instants, the addition of second-order kernels represents up to 100% improvement, but only for rotational stimuli. We present a perturbative scheme to facilitate the application of our method to weakly correlated neurons.

Abundância e sazonalidade de dípteros (Insecta) em granja aviária da região nordeste do Estado de São Paulo, Brasil

Modem production systems accommodate broody hens in high densities, leading to the accumulation of excrement under the cages. This substrate is excellent for the development of sinantropic flies. Thus, the accomplishment of surveys in these places becomes essential, in order to plan better strategies of control. The present work aimed at studying the entornofauna and the seasonality of the species of dipterous present in the Crisdan poultry house located in the Municipality of Sao Joao da Boa Vista, the State of São Paulo, Brazil. In the period of January of 2001 to December of 2002, 1,012,595 flies were captured using the "jug-trap". The species were identified: Drosophi-la repleta (Wollaston, 1858), Musca domestica (Linnaeus, 1758), Ophyra spp., Hennetria illucens (Linnaeus, 1758), Fannia canicularis (Linnaeus, 1761), Chrysomya megacephala (Fabricius, 1794), and Sepsidae. More frequently D. repleta and M. domestica had added 99.47% of the dipterous. Increased rainfall and the collection months influenced the sampling of dipterous (P < 0.05). Drosophila repleta was the most abundant species, representing 91% of all captured flies. However, this diptera did not develop at the surveyed site since immatures were not captured therein.

Survival rate, body size and food abundance in pure and mixed blowfly cultures

The influence of food abundance, larval density and interspecific interactions on the survival and body size of Chrysomya albiceps, Chrysomya megacephala and Cochliomyia macellaria was investigated in pure and mixed cultures, to determine the impact of competition and/or facultative predation on native and introduced blowfly species in South America. In mixed cultures there was complete elimination of C. megacephala and C. macellaria. Chrysomya albiceps exhibited higher survival in mixed compared to pure cultures, suggesting that predation offers more advantages than competition for food. Body size of C. albiceps was significantly affected by food scarcity in pure cultures. However, tibia size in males of all species suffered no significant variation as a function of food scarcity. The implications of these results for population dynamics of introduced and native blowfly species are discussed.

Stochastic dynamics in exotic and native blowflies: an analysis combining laboratory experiments and a two-patch metapopulation model

In this study we explored the stochastic population dynamics of three exotic blowfly species, Chrysomya albiceps, Chrysomya megacephala and Chrysomya putoria, and two native species, Cochliomyia macellaria and Lucilia eximia, by combining a density-dependent growth model with a two-patch metapopulation model. Stochastic fecundity, survival and migration were investigated by permitting random variations between predetermined demographic boundary values based on experimental data. Lucilia eximia and Chrysomya albiceps were the species most susceptible to the risk of local extinction. Cochliomyia macellaria, C. megacephala and C. putoria exhibited lower risks of extinction when compared to the other species. The simultaneous analysis of stochastic fecundity and survival revealed an increase in the extinction risk for all species. When stochastic fecundity, survival and migration were simulated together, the coupled populations were synchronized in the five species. These results are discussed, emphasizing biological invasion and interspecific interaction dynamics.

Dynamics of experimental populations of native and introduced blowflies (Diptera: Calliphoridae): mathematical modelling and the transition from asymptotic equilibrium to bounded oscillations

The equilibrium dynamics of native and introduced blowflies is modelled using a density-dependent model of population growth that takes into account important features of the life-history in these flies. A theoretical analysis indicates that the product of maximum fecundity and survival is the primary determinant of the dynamics. Cochliomyia macellaria, a blowfly native to the Americas and the introduced Chrysomya megacephala and Chrysomya putoria, differ in their dynamics in that the first species shows a damping oscillatory behavior leading to a one-point equilibrium, whereas in the last two species population numbers show a two-point limit cycle. Simulations showed that variation in fecundity has a marked effect on the dynamics and indicates the possibility of transitions from one-point equilibrium to bounded oscillations and aperiodic behavior. Variation in survival has much less influence on the dynamics.

Larval predation on different instars in blowfly populations

Chrysomya albiceps (Diptera: Calliphoridae) é uma predadora facultativa sobre outras moscas-varejeiras, durante o terceiro instar larval. Nesse estudo, nos investigamos a taxa de predação de C. albiceps sobre larvas de primeiro, segundo e terceiro instar de C. megacephala e C. macellaria comparando a vulnerabilidade dos instares larvais frente à predadora. Para as presas de primeiro e segundo instar, C. albiceps apresentou maior taxa de predação sobre C. megacephala. Já sobre larvas de terceiro instar a predadora consumiu mais C. macellaria. O comportamento de C. albiceps sobre as duas espécies de presas sugere uma mudança na estratégia de forrageio da predadora e essa mudança pode ter influencia sobre a comunidade de dípteros necrófagos.

Nutritional ecology of blowflies (Diptera, Calliphoridae): estimates of critical larval weight for pupation on two different diets

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Diversity and Synanthropy of Calliphoridae (Diptera) in the Region of Rio Claro, SP, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)