Guilherme Gomes

A preliminary study of insect fauna on pig carcasses located in sugarcane in winter in southeastern Brazil

Minimum post‐mortem intervals can be estimated based on analyses of the pattern of insect succession on a carcass. In order to successfully apply this approach, insect development rates must be considered with regard to local regional climatic conditions. This study is the first to analyse insect succession on carcasses decomposing in a sugarcane crop in Brazil. In all seasons, Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae) and Cochliomyia macellaria (Fabricius) were frequent visitors during the fresh and bloated stages of decomposition, whereas Dermestes maculatus (De Geer) (Coleoptera: Dermistdae), Necrobia rufipes (De Geer) (Coleoptera: Cleridae) and Oxelytrum sp. (Coleoptera: Silphidae) were characteristic at the most advanced decomposition stages. The fact that climatic variations influence the occurrence of insect species and vegetation in the tropics may help to solve crimes through sampling of the local insect fauna, as may the fact that only certain groups of insects occur in specific regions of large countries like Brazil.

The Effect of Buscopan® on the Development of the Blow Fly Chrysomya megacephala (F.) (Diptera: Calliphoridae)

Abstract:  This work investigated the effects of butylscopolamine bromide, a drug present in the pharmaceutical formulation Buscopan®, on the development of Chrysomya megacephala, a blow fly species of considerable forensic and medical importance in Brazil. Larvae exposed to the drug showed a decreased rate of development, with higher drug concentrations further retarding the development. Besides, larvae reared on the presence of the drug showed smaller body weight and body length when compared with larvae reared on the absence of Buscopan®. The drug also affected the mortality of the species.

Interação entre fatores visuais e olfativo em localização de recursos pela mosca-varejeira, Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae), em condições naturais

The interaction between olfactory and visual cues in the landing responses of Chrysomya megacephala (Fabricius) was analyzed in a natural environment (grass) using three plain cardboard circles with the colors white, black and other being the own grass (control) with 30 cm in diameter. The circles were divided in four quadrants and five sectors using as bait 80 mg of carcass of fish and minced flesh put in the center. To check the interaction between visual and olfactory factors, we analyzed the relation among the direction of wind and the sectors, the quadrants and the color of circle where C. megacephala adults landed. In the presence of the black and white circles, flies landed closer to the central release point of the bait when the wind was present compared with the other control circle. The results show that while odor cues may enhance the induction of landing by C. megacephala, visual cues are important when selecting a final landing site. Improved understanding of this interaction may allow the development of more effective traps or targets, enhancing the control efficiency of these control devices.

Occurrence of Hymenoptera on Sus scrofa carcasses during summer and winter seasons in southeastern Brazil

Considerable importance has been given to nest construction and larval food transport to the nest as a precondition for the eusociality of insects. Most adult hymenopterans feed on liquids, although bees and a few wasps may also feed on pollen. Carrion represents an additional source of protein for some species and they will scavenge for dead animals in the wild. This paper aims at analyzing Hymenoptera visitors on a pig carcass during the process of decomposition, in the summer of 2005 and the winter of 2006 in Brazil, and comparing the results with other studies in the Neotropical region. To our knowledge, this is the first study which described the occurence of Agelaia pallipes, Polybia paulista and Scaptotrigona depilis on decomposing carcasses in southeastern Brazil. It also raises the hypothesis of possible applications of Hymenoptera to achieve more precise PMI estimations, apart from other insects already known as having great importance in such estimates.

Foraging by Polybia (Trichothorax) ignobilis (Hymenoptera, Vespidae) on flies at animal carcasses

Foraging by Polybia (Trichothorax) ignobilis (Hymenoptera, Vespidae) on flies at animal carcasses. Proteins for brood nutrition of social wasps are obtained from many prey, including insects (even bees and other wasps), spiders and bits of decaying meat. After being captured and killed, prey are reduced to a shapeless mass and distributed to the brood. Little is known about the foraging activity, especially on this group. Herein we describe the sequence of foraging behaviours of the social wasp Polybia (Trichothorax) ignobilis for hunting flies (Diptera: Calliphoridae and Muscidae) over pig carcasses. To our knowledge, there are few scientific descriptions of prey foraging behaviour on this species.

The Influence of Temperature on the Behavior of Burrowing in Larvae of the Blowflies, Chrysomya albiceps and Lucilia cuprina, Under Controlled Conditions

Abstract Blowflies use discrete, ephemeral substrates for larval development. After exhaustion of the food supply, larvae will disperse in search of sites to burrow and pupate or will seek other sources of food in a process known as post-feeding larval dispersal. In this study, the effect of temperature was investigated as it is one of the most important aspects of the environmental variables in this process. 800 larvae of the blowflies Chrysomya albiceps (Wiedemann 1819) and Lucilia cuprina (Wiedemann 1830) (Diptera: Calliphoridae) were incubated in tubes covered with vermiculite at 15, 20, 25 and 30°C. For each pupa, the body weight, sex and depth of burrowing were determined. Statistical tests were used to examine the relationship of depth of burrowing and body weight to the temperature at which burrowing occurred. Depth of burrowing was affected differently by temperature for both of the species studied; L. cuprina larvae burrowed deeper at lower and higher temperatures while C. albiceps larvae burrowed less at extreme temperatures. Additionally, temperature had a significant effect on the body weight of L. cuprina larvae as body weight decreased as temperature increased, whereas for C. albiceps, pupal weight increased up to 25°C and then decreased abruptly at a higher temperatures. The maximum body weight was also differently affected in the two species; in L. cuprina, the maximal weight was at 15°C and for C. albiceps weight was maximal at 20°C.

Influence of photoperiod on body weight and depth of burrowing in larvae of Chrysomya megacephala (Fabricius) (Diptera, Calliphoridae) and implications for forensic entomology

Blowflies use discrete, ephemeral breeding sites for larval nutrition. After exhaustion of the food supply, the larvae disperse in search of sites to pupate or to seek other sources of food in a process known as post-feeding larval dispersal. In this study, some of the most important aspects of this process were investigated in larvae of the blowflies Chrysomya megacephala exposed to a variety of light: dark (LD) cycles (0:0 h, 12:12 h and 24:0 h) and incubated in tubes covered with vermiculite. For each pupa, the body weight and depth of burrowing were determined. Statistical tests were used to examine the relationship of depth of burrowing and body weight to photoperiod at which burrowing occurred. The study of burial behavior in post-feeding larval dispersing can be useful for estimating the postmortem interval (PMI) of human corpses in forensic medicine.

Efeito do tipo de substrato para pupação na dispersão larval pós-alimentar de Chrysomya albiceps (Diptera, Calliphoridae)

Blowflies utilize discrete and ephemeral sites for breeding and larval nutrition. After the exhaustion of food, the larvae begin dispersing to search for pupation sites or for additional food sources, a process referred to as postfeeding larval dispersal. However the nature of the substrate can affect this process. Some of the most important aspects of this behavior were here investigated in Chrysomya albiceps (Wiedemann, 1819), utilizing a circular arena covered with vermiculite allowing the post-feeding larval dispersal from the center and to comparing with others studies that used sawdust. To determinate the location of each pupa, the arena was divided into 72 equal sectors from the center. For each pupa, weight, dispersal distance from the center of arena, and depth were determined. Statistical tests were performed to verify the relationship among weight, depth and distance of burial for pupation. The larvae that dispersed farthest were those with lower weights, as in other studies that employed other substrates. The majority of individuals reached the burial depth for pupation between 2 and 8 cm (mean 4.96±2.97 cm). The study of this dispersal process can be helpful in the estimation of postmortem interval (PMI) for human corpses in medico-criminal investigations.

Evolutionary Modeling of Larval Dispersal in Blowflies Using Non-Uniform Cellular Automata

When the food supply finishes, or when the larvae of blowflies complete their development and migrate prior to the total removal of the larval substrate, they disperse to find adequate places for pupation, a process known as post-feeding larval dispersal. Based on experimental data of the initial and final configuration of the dispersion, the reproduction of such spatio-temporal behavior is achieved here by means of the evolutionary search for cellular automata with a distinct transition rule associated with each cell, also known as a nonuniform cellular automata, and with two states per cell in the lattice. Two-dimensional regular lattices and multivalued states will be considered and a practical question is the necessity of discovering a proper set of transition rules. Given that the number of rules is related to the number of cells in the lattice, the search space is very large and an evolution strategy is then considered to optimize the parameters of the transition rules, with two transition rules per cell. As the parameters to be optimized admit a physical interpretation, the obtained computational model can be analyzed to raise some hypothetical explanation of the observed spatio-temporal behavior.