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To see how Blowfly larvae (Calliphora) react to light.

Extracts from this document...

Introduction

THE EFFECT OF LIGHT ON BLOWFLY LARVAE (CALLIPHORA) AIM To see how Blowfly larvae (Calliphora) react to light. BACKGROUND KNOWLEDGE The Blowfly is any member of the insect family Calliphoridae (order Diptera). They are metallic blue, green, or black in colour and are noisy in flight, producing a distinctive buzzing sound. The blowflies are on average 8-10 mm in length, slightly larger than the more common housefly larvae. Among the blowfly family, the more important members are the screwworm, bluebottle fly (Calliphora), green bottle fly, and cluster fly. Adult blowflies feed on a variety of materials, but the larvae of most species are scavengers that live on carrion or dung. The adults lay their eggs on the carcasses of dead animals, the eggs hatching in less than a day and the larvae burrow straight down into the food source, and feeding on the decaying flesh. The larvae of some species also sometimes infest open wounds of living animals. Several days before going into the pupal state, the blowfly larvae tend to move away from light source, often ending up under carpets or behind panelling. After 8-10 days the pupae wriggle their way into the light and the adult flies emerge. They are immediately able to fly off, mate and start laying eggs. Stereotyped responses are the unlearned behavioural reactions of an organism to some environmental stimulus. ...read more.

Middle

The next factor that I had to consider was the time intervals between marking the progress of the larvae. METHOD: To ensure that the following method can easily be followed, make sure all apparatus that needs to be used is within in easy reach as the experiments are carried out in the dark. Firstly set up the apparatus whilst the lights in the room are still on. Make sure that the circle of paper placed beneath the lamp is put in the correct way; the positive sector nearest the lamp with the negative furthest away. After the apparatus is set up, remove the larvae from the fridge and allow them to sit for 10 minutes so they reach room temperature. Once everything is ready, turn off all the light in the room, close all the blinds; as a result the room is lit only by the lamp being used in the experiment. When ready, spin the pencil to provide a random direction in which to place the maggot. Place the maggot in the inner circle. As soon as the tail of the maggot leaves the circle, start the stopwatch. Make a mark on the inner circle to show the spot from where the maggot left. Here on, until the maggot reaches the outer circle, mark the movement every five seconds. ...read more.

Conclusion

The actual distance covered by the maggot in those five seconds was more than 4.5cm. An error arose here because the maggot was moving towards the light source, so it displacement was far less than the distance it had travelled. This error led to an inaccuracy in the speed that the maggot was moving. Other minor problems were also encountered. The first of these is that it was impossible to remove all background light from the laboratory. With all the blinds and doors were closed; there was some light from the extractor fan entering the room. I think that the effect of this small light source was negligible. This is because the light was entering from high on the walls and from the opposite end of the laboratory. Another problem that was came across was the heating effect that the lamp was having on the paper circle and as a result on the maggot. This factor may have played a crucial role in the experiment as the maggots may not have been just moving away from a light source, they may also have been moving away from a heat source. FURTHER INVESTIGATIONS: To further investigate this experiment, see the effect of changing the intensity of white light on how the maggot moves, whether it is faster or slower, or the average angle they travel is considerably different. Another further investigation would be to find out what effect different colours of light have on the orientation of the maggot. ...read more.

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