Forensic Entomology

What you need

• 1 pencil or other writing utensil • 3 larva colony charts, included in this activity guide • 1 Larva Development Table, included on the final page of this activity guide

Preparation

Review the following scenario: Several pieces of evidence were brought into a wildlife forensics lab. They are the remains of animals, but wildlife forensic investigators are not sure what type of animal. They plan to skeletonize them to study the bones and determine the type of animal and some other information about it. Unfortunately, the specimens, which were already starting to decay when they were collected and brought to the lab, had been contaminated by insects, and they invaded the lab’s dermestid colonies.

What to do

Below you will see three charts that represent the three different larva colonies that contaminated the lab’s dermestid colonies. In order to determine the age of the larvae in each colony, use the Larva Development Table found at the end of this document. Find the correct insect larva on the table and then find its length, recorded on the table. Then determine the number of days since initial contamination on the table. Write the correct number in the chart.

The first chart has been completed as an example.

1. Example Lab Dermestid Colony #1 Larva Length Days since initial contamination Cheese Skipper 10 mm 11

Flesh Fly 36 mm 6

House Fly 28 mm 10

House Fly 30 mm 10

Review a sample of the table below to see how the days since initial contamination were determined.

These circles correspond to larvae from the first chart (Lab Dermestid Colony #1). The arrows indicate the days since initial contamination determined by the larva’s size. It has been between 6 and 11 days since initial contamination by the larvae. 2. Lab Dermestid Colony #2 Larva Length Days since initial contamination Blue Bottle 29 mm Fly Cheese Skipper 16 mm

Cheese Skipper 13 mm

House Fly 30 mm

House Fly 20 mm

3. Lab Dermestid Colony #3 Larva Length Days since initial contamination Cheese Skipper 13 mm

Cheese Skipper 16 mm

House Fly 27 mm

Blue Bottle 29 mm Fly

What is happening?

Forensic entomology is the study of insects and other arthropods and how they interact with forensic investigations.

After an animal dies, insects will lay eggs in and on the body. For many insects that undergo complete metamorphosis (a four-stage life cycle) the eggs will then become larvae that feed upon the dead animal’s body before they pupate and then become adults. Other insects undergo incomplete metamorphosis (a three- stage life cycle) where eggs hatch into nymphs that feed on the dead animal’s body. This sounds gross, but without these insects, earth would be covered in dead animal bodies! Different insects arrive at different stages after death. Forensic entomology can help to determine how long ago an animal died based on what insect species are present, what life stage they are at, and how large they are.

Answers

1. Lab Dermestid Colony #1 Number of days since initial colonization: 6-11 2. Lab Dermestid Colony #2 Number of days since initial colonization: 8-12 3. Lab Dermestid Colony #3 Number of days since initial colonization: 10-12