Investigation of the Behavior of Blowfly Larvae

Introduction

The blowfly goes through a complete metabolic change in body form at each stage in their life.

- Stage 1 - Egg

- Stage 2 - Larvae

- Stage 3 - Pupa

- Stage 4 - Adult

Adult -- Blowflies are a group ranging from 6 to 14 mm in length. The black Blowfly has a dark, olive-green body, black legs, and orange pubescence around the spiracles. All Blowflies have blunt mouthparts and do not bite.

Egg -- The white or pale yellow eggs of Blowflies may occur in small batches or large masses. Individual eggs are about 1.5 mm long.

Larvae -- These white to yellowish maggots have pointed heads. They develop through three instars and become 12 to 18 mm long when fully grown.

Pupa -- Blowfly pupa are encased in light brown to black puparia (the tough, hardened skins). Each puparium is 9 to 10 mm long and 3 to 4 mm wide.

In my investigation I will be only working with larvae (Stage 2 in the cycle). The larvae is the main feeding stage of the fly. There are 3 inistars. On hatching, first-instar larvae are roughly 2 mm long, growing to about 5 mm before shedding their skin. The second instar larvae grow to around 10 mm before they shed their skins to become third-instar larvae. Third-instar larvae grow to between 15 mm and 20 mm.

Hypothesis for Experiment 1

My hypothesis is I need to investigate the behavior of Blowfly Larvae in different light conditions. In this experiment I will be seeing how the larvae react to a direct light source from above.

The Equipment that was used in Experiment 1

- 10 Blowfly larvae

- Simple choice chamber

- See-through lid for choice chamber

- A circle with a pencil line down the middle

- Stopwatch

- A lamp

What Happened in Experiment 1

My partner and I first got all the equipment above setup and ready on a workbench. I then got a glass beaker with the 10 larvae located inside it. We then both checked that there where exactly 10 larvae inside the beaker. My partner then carefully placed the 10 larvae into the choice chamber (We made sure it was close to the middle line). I then waited for 10 seconds while the larvae spread out. I then began timing and my partner shouted out how many larvae where on the left and right every minute and I wrote down the results.

About 4 minutes through our first run of the experiment our teacher saw that the ambient light inside the classroom was not good enough for the experiment to be accurate. Originally for the larvae experiments our teacher thought that the ambient light inside the room would be enough. But later it was realized that the light inside room was not enough, so we used lamps.

We then took the larvae out of the choice chamber and setup a lamp directly above the choice chamber; we made sure that the lamp was not too close to the chamber. My partner then placed the Larvae into the middle of the choice chamber, I then waited 10 seconds for the larvae to spread out and I began timing again. The second experiment ran well with no problems, and we recorded for 10 minutes and recorded the results

Results For Experiment 1

Time 1 2 3 4 5 6 7 8 9 10

Left 3 2 3 2 4 6 8 6 4 4

Right 7 8 7 8 6 4 2 4 6 6

Graphs For Experiment 1

I generated a line graph for experiment one titled " Larvae choosing between left and right above lamp "

Conclusion Of Experiment 1

They are moving around randomly because there is no way of getting away from the light source. At some times they prefer the right hand side (at 4 minutes) and other times the left (at 7 minutes)

Possible Effects in Experiment 1 That may differ results

- Larvae may have been effected by the lamp being too close to the choice chamber

- If the larvae are in the middle, it is hard to see which side they are on.

- The circle may have been cut in-accurately and one side could be bigger than the other.

- If the choice chamber is not cleaned properly the Larvae could come into contact with chemical stimuli (e.g. Calcium Chloride)

How Experiment 1 could be improved

- We could have measured the distance between the lamp and the choice chamber to make sure the light was not too close

- We could have tracked each larvae to see how there behavior changed from when they entered the choice chamber

- The circle could have been measured from the middle to see if the right side and the left side was accurate

- We could have repeated the experiment to see if our results where accurate

Hypothesis for Experiment 2

I need to investigate the behavior of Blowfly Larvae in different light conditions. In experiment 2 I will be seeing if the Blowfly Larvae prefer light or dark conditions. The big change in experiment 2 is that we are replacing the see through lid with one, which is half dark and half see-through. What I think will happen is the larvae will move into the darkness.

The Equipment that was used in Experiment 2

- 10 Blowfly larvae

- Simple choice chamber

- A half dark and half see through lid.

- A circle with a pencil line down the middle

- Stopwatch

- A lamp

What Happened in Experiment