FS15 Activity: Forensic Entomology Name ___________________________ Objectives: 1) Investigate insect life cycles and review the concept of niche. 2) Practice critical thinking and problem solving using metric measurements and conversions. 3) Illustrate how knowledge of basic biology can lead to practical usage in criminal investigations. Introduction: You have been introduced to some of the concepts of ecology and the life cycles of flies. You will be using this information to help determine when a person died. In addition, you might determine facts about the murder such as the involvement of drugs, areas of wounding on the body, or if a body was moved after death. Time of death can be important corroborating evidence. If a suspect does not have a legitimate alibi at the calculated time of death, they might have had access to the victim. You will model the action of a forensic entomologist, measuring the sizes of “lanyard flies” collected from an imaginary deceased person. The size of the flies will determine their age in days. The age of the insects collected on a dead body generally tells you how long the body has been exposed. The postmortem interval (PMI) is the amount of time since the body was exposed to flies. The time of death (TOD) is can be determined from the PMI and is usually the same as the PMI. Using insect information along with environmental factors, you will try to determine the PMI, location of death, and/or cause or circumstances of death. Materials: case data form Plastic “maggot ” bag metric ruler Directions: Sorry to disappoint you but we can’t take a field trip to the scene of the crime. Instead, you will be given a typed ,“Case Report for Forensic Entomology.” This report was prepared by the crime scene investigator who collected the maggot sample to send to you, the Forensic Entomologist. Check off each activity as you complete it for your case. Note: The Forensic Entomology Data Form and Data Table for Insect Specimens should be in black ink. If you want to use pencil, make sure to go over it with a black pen before handing in. You can also make a copy of the page and it will come out black. Otherwise, download and type into a blank file from the class website.

___1) Read the Case Report and fill out a blank “Forensic Entomology Data Form.” Data forms are a way to organize the information you get from the crime scene investigator so that you can compare cases without having to read all through all the information in the report. For example, if you wanted to compare the temperatures that maggots experienced at two different crime scenes, you could easily find the information on the two data forms under “Scene Temperatures.” NOTE: You must include all the information from the case report even if it seems irrelevant to the case. It is not that important where the information is on the report—just that it is somewhere on the data form. ____2) You will be given a sample bag containing small sections of colored plastic lanyard (model ‘maggots’). Organize the lanyards based on color and determine the species of each ‘maggot’ by using Table #2. Fill out the “Data Table For Insect Specimens” by listing the species of each ‘maggot’ on the chart. Use the proper format for recording scientific names. Genus is capitalized, species is lower case. Both names are underlined. If typing the name, use italics (ex. Musca domestica or Musca domestica). If the color of the lanyard indicates the fly is in the pupa form, determine the species based on the length. ____3) Use a metric ruler to measure each ‘maggot.’ Record this measurement in millimeters (10 mm=1cm) next to the name of the ‘maggot’ in the column labeled “Length in mm.” ____4) Use Table 1 to determine the approximate age of each ‘maggot.’ The age of the oldest insects will give you the time that the body was first exposed to fly egg laying. If you have a pupa, read note “g)” under ‘Important Points to Consider…’ on page 3. ____5) The data in Table 1 is based on a temperature of 22 oC. You need to determine the average temperature that your maggots experienced during their growth. This may not be the temperature when the body 1

was found. Use all of the information in the report to determine the best temperature to use. ____6) The average temperature on your case report may be in oF. If this is the case, you will need to convert the average temperature to oC. Use the following equations to convert the temperature in your report: o

C = ( oF – 32) x 5/9

o

F = oC x 9/5 + 32

____7) If the average temperature at your scene is different from 22 oC, you will need to adjust the age of your larvae. Use Table 3 to determine the actual age of your larvae. Record your adjusted age in the column labeled, “Age (days) adjusted for a temp of ____oC.” Include the average temperature in the blank space. A) If the temperature at the crime scene is greater than 22 oC, the growth of larvae with be speeded up and they will appear older than they actually are. You must subtract the number of days in the table in order to obtain the correct age. Example: Temperature at scene: 29 oC Musca domestica development is accelerated (speeded up) by 3 days Age of larvae based on length of lanyard at 22 oC = 7 days Actual age of maggot adjusted for temperature 7-3 = 4 days B) If the temperature at the scene is less than 22 oC, the growth of larvae will be slowed and they will appear younger than they actually are. You must add the number of days in the table in order to obtain the correct age. Example: Temperature at scene: 18 oC Musca domestica development is accelerated (slowed) by 1 day Age of larvae based on length of lanyard at 22 oC = 3 days Actual age of maggot adjusted for temperature 1+3 = 4 days ____8) Certain environmental factors like drugs will also speed or delay development of fly larvae. If your crime scene indicates that the victim took drugs, you will need to adjust the age of your larvae based on those drugs. Use table #3 to determine if you need to add or subtract days for drugs.

____9) If you have BOTH temperature and drug adjustments in your crime scene, adjust for temperature first and then adjust the new values you have obtained for drugs. Example: Temperature at scene: 18 oC Calliphora vomitoria development is accelerated (slowed) by 3 days Age of larvae based on length of lanyard at 22 oC = 3 days Actual age of maggot adjust for temperature 3+3 = 6 days Drugs at scene speed development by 3 days Actual age of maggot adjusted for temp and drugs 6-3 = 3days ____10) Read “IMPORTANT POINTS TO CONSIDER WHEN TRYING TO DETERMINE THE PMI” You will need to determine if any of the points are important in your case. If so, you will need to follow the directions or you will not interpret your data correctly.

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IMPORTANT POINTS TO CONSIDER WHEN TRYING TO DETERMINE THE PMI a) Egg laying by flies can occur as soon as 10 minutes after death. Thus, the time of death (TOD) coincides with the first egg laying by flies. If you can determine the age in days of a pupa or maggot on a corpse, you essentially have the PMI (post mortem interval) or number of days since the body was first exposed to flies. In most cases the TOD is the same as the PMI. An exception might be if the body is tossed into a freezer before it is exposed to flies. The TOD and PMI won’t be the same! b) On observation, you may find maggots of several different sizes. This is due to several factors. First, adult flies will continue to lay eggs on the corpse for a number of days. Maggots of the same species that develop from eggs laid on different days will be different ages. In addition, different species of flies develop at different rates and are attracted to the corpse at different stages. The OLDEST MAGGOTS OR PUPAE will indicate the PMI. c) Flies go through several instars or stages of development. Each instar measures an approximate length. If you collect a sample of maggots from a corpse, and measure their sizes, you can determine what instar you have. Based on data tables that show age of instars based on size, you can determine the age of the maggot. See Table #1. The same goes for pupae but refer to comment ‘g’ below. d) Insects are cold-blooded. They depend on the temperature in their environment to maintain body temperature so that metabolic functions like growth can take place. Growth of fly larvae is speeded up at higher temperatures. Growth is slowed at lower temperatures. See Table #3. e) Other environmental factors can influence the growth of fly maggots. See Table #3. 1. Shaded environments usually have lowered temperatures. Corpses in shaded areas will yield slower growing maggots due to lower temperatures. 2. Drugs like cocaine and Ecstacy can speed development of some species of maggots. Other poisons like Malathion (insecticide) and arsenic can slow development of maggots. If a larva that is sensitive to the effects of drugs measures as a 6 day old larva, and cocaine is found in the body, the larva is only 3 days old! See Table #3. 3. Habitat can give clues to the types of flies that lay eggs on the body. Some species are unique to rural areas, some urban and some found in all types of habitats. A body found in a field that harbors urban maggots may have been transported to the site, from an urban area, after death. This indicates foul play (an illegal action) on the part of a suspect! 4. Location of the maggot mass can indicate if trauma has occurred. If a maggot mass is found in an area not normally infested such as the upper torso or head, it indicates that the body had damage in that area that would attract egg laying. f) The United States has NOT converted to the metric system. Are you more familiar with a temperature of 98.6 oF or 37 oC? They are both the same! Be aware of this when you analyze your information. g) Nothing is exact in insect development. If the cadaver contains pupae, you won’t be able to tell exactly how old they are. For example, if you have Calliphora vomitoria pupae, they could be anywhere from 14 to 20 days old. If BOTH larvae and pupae of a species are present, use the youngest day for the PMI of the pupae. If only pupae are present, use the oldest date as the PMI. In our example, use 14 days if both larvae and pupae of C. vomitoria are present and 20 days of only pupae are present. h) Scavengers like small reptiles and rodents will nibble at exposed areas of the body. This is not foul play. It is just natural feeding by scavengers. 3

____ 11) TYPE A REPORT: This report will be sent to the detectives, judge, and attorneys recording your results and interpretation of the insect data. This information may be used in court, so make sure it is in a professional format. Add a header for the forensic entomology company or university that you work for. Example:

Maggots R US PMI Research Co. Maggotville, CA 95220 PH: 818-765-8907 Entomology Report for Case #1 I. Introduction to, and Synopsis of Case: II. Determination of PMI: III. Final Conclusions: (Add additional comments for each case here!) Submitted by:

Tod McGruesome,

PhD, Forensic Entomologist

I. Paragraph I. Start with an introduction and synopsis of the case. Write an introduction that describes the important details of the crime scene. You don’t have to include the trivia like the temperature of the maggot mass but you should use enough to paint a picture of the scene. Include important information about the temperature, if drugs were involved, if there was trauma to the body, etc. II. Determination of the PMI: Explain in words HOW you determined the PMI. a) Describe the number of maggots or pupae you had in the sample. Talk about how many of each species you identified. Include the scientific names. b) Explain if you had to correct for temperature, drugs, environmental differences, or if there were unusual species on the body that are not normally found in the area. c) Describe how you determined the PMI. What number of days did you use? How did you correct for drugs, temperature, environmental differences, etc. Include the following: a. How did you use the table? b. How did you figure out the ages c. What were the ages of the oldest larvae or pupae. III. Final Conclusion: Restate the PMI. What date was the body exposed to insects? How long has the person been dead? Were there any other aspects of the crime that are important? (Example, was the body moved? How did you know?) Make sure you add the answers to the “Additional comments for Each Case” listed on the next page. Some of your information may go better in II than in III. Put it where you think it works the best. Typing note: to make oC or oF, hold Ctrl+Shift and type ‘ +’ to enter and exit superscript mode. Type a temperature as 24 oC, not 24oC or 24o C. 4

ADDITIONAL COMMENTS FOR EACH CASE: Look for your case number below. Make sure you include the following information in your report under the section: Final Conclusions. a) Case #1: Why are maggots of different lengths found on the body? Besides temperature, what abiotic conditions would you want the police department to obtain from the weather stations around the site in order to be more confident of your estimations? Propose a reason for the discrepancy between your findings and the witness statement. Explain. b) Case #2: What effect did the outside temperature have on your estimation of the time of death? How did the fact that the windows were closed relate to the populations of flies you observed in and around the corpse? (Compare this case to case #1). Why didn’t you collect any Calliphora vomitoria? Do you suspect foul play? Explain. c) Case #3: What effect did temperature and cocaine have on your estimation of time of death? How did you use this information to determine the PMI? Explain exactly how many days were used to adjust the data for the presence of cocaine. Were the types of insects sampled consistent with the location that the body was found in? Based on the data, can you determine if foul play was involved or was this a simple case of overdose? d) Case #4: What effect did temperature have on your estimation of time of death? How did you use this information to determine the PMI? Does the location of the body, coupled with the insects recovered from it, suggest foul play or not, or can you tell from the information given? Explain.

Table 1. The development of body length (mm) of some fly species during their metamorphosis at 22 oC. # Age of egg, larva(L) or pupae (P) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

(L=larva or maggot, P=pupa, A=adult fly) Musca domestica Calliphora vomitoria

egg egg L6 L6 L 7-11 L 12-16 L 17-20 L 21-25 L 26-30 L 31-35 P 26-29 P 26-29 P 26-29 P 26-29 P 26-29 P 26-29 A 30-32

egg L 9-11 L 9-11 L 12-16 L 12-16 L 17-20 L 17-20 L 21-25 L 21-25 L 26-30 L 26-30 L 31-35 L 31-35 P 31-34 P 31-34 P 31-34 P 31-34 P 31-34 P 31-34 P 31-34 A 36-38

Sarcophaga carnaria L 9-11 L12-16 L17-20 L 21-25 L 26-30 L 31-35 L 36-40 L 41-43 L 44-46 L 44-46 P 38-40 P 38-40 P 38-40 P 38-40 P 38-40 P 38-40 P 38-40 P 38-40 A 42-45

Piophila nigriceps

egg egg L3 L3 L 4-6 L 7-9 L 10-13 L 14-16 P 13-15 P 13-15 P 13-15 P 13-15 P 13-15 P 13-15 A 16-18

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Table 2:

Color Key for ‘Maggots”

Note: In most cases, live samples are collected off the body and must be reared to adulthood to determine the species of fly. In this exercise, the species of fly will be determined by the color of the ‘larvae.’ Musca =white

Calliphora =blue

Sarcophaga=orange

Piophila=red

**All pupae are black/red in color. Use the length of each pupa to help determine the species.**

Table 3. Ecological information for certain species of flies. The developmental delays/accelerations are given in # of days relative to the developmental schedule in Table 1 for 22 oC.

Musca domestica Temperature (oC)

13 18 27 29

delayed 4 delayed 1 accelerated 1 accelerated 3

Environmental Factors

Habitat Drugs

urban and rural no effect

Calliphora vomitoria delayed 4.5 delayed 3 accelerated 2 accelerated 4

Sarcophaga carnaria delayed 4 delayed 2 accelerated 1.5 accelerated 3

Piophila nigriceps delayed 3 delayed 1 accelerated 1 accelerated 2

urban and rural

urban and rural no effect

urban no effect

speeds development by 3 days

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DATA TABLE FOR INSECT SPECIMENS

Case number: ____________ Measure the length of the maggots and pupae in the preserved specimens that were sent to you by the police department. Fill in the following chart. Depending on the facts of your case, you may or may not have to adjust the PMI for drugs and/or temperature differences. Color of specimen

Length in mm

Genus and SpeciesNote: The genus name is always capitalized and underlined. The species name is lower case and underlined. The second entry for any name can be abbreviated: ex. C. vomitoria or you can use dittos (“).

Age(days) for specimen at 22 oC

Age (days) adjusted from a temp of __________oC +/-

Age(days)

Age (days) adjusted for temperature (if needed) and drugs +/Age (days)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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