Dead or Alive?

PHASE 1 : Background Information

Insects can be used to estimate the post-mortem interval by identifying how long a person has been dead. There are many types of insects used in forensic entomology. Some types include blow flies, ants, bees, wasps, moths, mites, and beetles. The stages of life a blow fly will go through are eggs, larva , pre-pupa, early and late pupa, and finally the adult stage. 

Image result for blow fly life cycle

Forensic entomology is reliable because it tells entomologist what they need to know about the time of the death.

PHASE 2: Write your hypothesis

The book claims that each stage of life will last 8 hours for eggs, 20 hours for Larva 1, 15-20 hours for Larva 2, 36-56 hours for Larva 3, 86-180 for Pre-Pupa, 6-12 days for Early and late Pupa, and 3 weeks for Adult phase. I think that the blowflies in our experiment will go through their life cycle at the same rate as the textbook. I chose this hypothesis because it seems that it would take this long to develop all stages.

PHASE 3: Build your experimental apparatus  

Apparatus from the first day:



We got a HEB plastic bakery container, and cut the top off with scissors. Then we wrapped the raw chicken in a piece of brown construction paper. It was built this way so that the blowflies could enter the container through the blue tub they were placed in and lay it’s eggs there. We also tried the brown construction paper to see how it would effect them by developing faster or slower instar and if there would be more pupa.

PHASE 4:  Data Collection

Stage        Size        Color       Stage& Time   Weather     Characteristic  Picture

Day 0:   N/A        N/A           12:03pm                      89 degrees    Raw chicken      img_4899-1

Day 5:   .7 cm      Off white    12:45pm/ Larva 1    87 degrees  Spikes        img_4962

Day 7:    1 cm        Light tan    12:10pm/ Larva 2   84 degrees    Tan,spikes   img_5023

Day 9:   .7 cm     Dark Brown    12:13pm/Pupae    84 degrees  It rained, spikes  img_5033

Day 14:   Adult fly  Green, blue, black   12:37pm/ Adult  84 degrees  Greenbottle Flyimg_5069-1img_5072

Since flies will continue to enter the container and lay new eggs we can account for this by taking the oldest pupa out the container and compare it with the smallest.

PHASE 5: Interpret and analyze your data

In conclusion, the textbook was not accurate due to the fact that my group was one of the groups that had the brown construction paper, our pupa became adults at a faster rate. My hypothesis was that the blowflies would go through their life cycle at the same rate as the textbook. My hypothesis was incorrect. We noticed that because our raw chicken was wrapped in the brown construction paper, flies were able to lay their eggs there a lot faster then the other containers without the paper. Next time we could test the different times of the eggs being layed with different papers around the chicken to see how it would change the life cycle rate. I’ve learned from this experiment that forensic entomology is sometimes very reliable, and sometimes not so reliable depending on different factors.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s