1. Honors Forensic Science
Chapter 8
Entomology

2. Forensic Entomology – The study of the insects associated with a human corpse related to legal issues.
1. Purpose of Forensic Entomology
A. Determine elapsed time since death – Not an exact time, only a close estimate.

3. B. Factors that affect insect deve-
lopment:
(1) Temperature
(2) Moisture (3) Wind (4) Season

4. (5) Variations among individual insects
(6) Exposure to the elements
(7) Time of day

5. C. Insect evidence may show that. the body has been moved to a
C. Insect evidence may show that the body has been moved to a 2nd site after death

6. D. Insect evidence may show that. the body has been disturbed at
D. Insect evidence may show that the body has been disturbed at some time, either by animals or by the killer returning to the crime scene

7. 2. Most cases that involve a forensic
2. Most cases that involve a forensic entomologist are 72 hours or more old
  A. Up to 72 hours after death – Other forensic methods are equally or more accurate than the
insect evidence.

8. B. 3+ days – Insect evidence is. often the most accurate and
B. 3+ days – Insect evidence is often the most accurate and sometimes the only method of determining elapsed time since death.

9. Two Main Ways of Using Insects to Determine Elapsed Time Since Death
1. Using succession waves of insects
  A. Used when the corpse has been dead between 1 month and up to a year or more

10. 2. Using maggot age and develop- ment:
A. Used when death occurred less than a month prior to discovery

11. Insects of Forensic Importance
Fly – Often the first insects to come in contact with a dead animal
1. Attracted to two gases of decompo-
sition:
A. Putrescine
B. Cadaverene

12. 2. Prefer a moist corpse for the maggots to feed on – Easier to chew

13. Blow-Fly
1. Lays eggs in carrion, wounds, or dung

14. Life Stages of Blow-Fly
1. Egg Stage
A. Size – 2 mm
B. Color – White
C. 1st Appearance – Within minutes after death
D. Stage Duration – 8 hrs

15. E. Characteristics:
(1) Found in moist, warm areas of the body

16. 2. Larva 1 (Instar 1)
A. Size – 5 mm
B. Color – White
C. 1st Appearance – hours
D. Stage Duration – 20 hrs

17. E. Larva 1 Characteristics
(1) Black mouth hooks visible (anterior side)
(2) Thin body
(3) One spiracle slit near anus

19. 3. Larva 2 (Instar 2)
A. Size – 10 mm
B. Color – White
C. 1st Appearance – 2 ½ days
D. Stage Duration – hours

20. E. Larva 2 Characteristics
(1) Black mouth hooks (anterior side)
(2) Actively feeding
(3) Dark crop seen on anterior dorsal side
(4) 2 spiracle slits near the anus

22. 4. Larva 3 (Instar 3)
A. Size – 17 mm
B. Color – White
C. 1st Appearance – 4-5 days
D. Stage Duration – hrs

23. E. Larva 3 Characteristics
(1) Black mouth hooks
(2) Crop not visible – Crop is covered by fat deposits
(3) Fat body
  (4) Three spiracle slits near the anus

26. 5. Pre-Pupa
A. Size – 9 mm
B. Color – Light brown
C. 1st Appearance – 8-12 days
D. Stage Duration – hrs
E. Pre-Pupa Characteristics
(1) Larva migrates away
from the body to a dry
area

27. 6. Early and Late Pupa
A. Size – 9 mm
B. Color – Light brown & changes to dark brown
C. 1st Appearance – days
D. Stage Duration – 6-12 days

28. E. Characteristics of Early and Late Pupa:
(1) Immobile
(2) Does not feed
(3) Changes to dark brown with age

29. (4). Filled air “balloon” to help. split open pupa case prior to
(4) Filled air “balloon” to help split open pupa case prior to emerging as adult

30. Early / Late Pupa

31. 7. Adult
A. Size – Varies
B. Color – Black or green
C. 1st Appearance – days
D. Stage Duration – Several weeks

32. E. Characteristics:
(1) Incapable of flight for first few hours

34. Flesh Fly
1. Medium-sized flies with black and gray longitudinal stripes on the thorax & checkering on abdomen
2. Do not lay eggs – Deposit newly hatched maggots directly onto the corpse.

36. House Fly
1. Characterized by a thorax that is gray with 4 dark longitudinal lines on the back; Abdomen is yellow
2. Breeds in moist or decaying organic matter

38. Beetles – Generally found on the corpse when it is more decomposed
1. In drier conditions – Beetles can be replaced by moth flies

40. Rove Beetles
1. Elongated bodies with small wing covers and large jaws
2. Have very fast larval development
3. Feed on larvae of all species of fly
4. Common only during the later stages of decomposition

42. Hister (Burrowing) Beetles
1. Usually shiny (black or metallic- green) beetles
2. Only become active at night – Feed on the maggot infested part of the corpse

43. A. Day – Hide under the corpse. unless it is sufficiently decayed
A. Day – Hide under the corpse unless it is sufficiently decayed to enable to hide inside it

45. Carrion Beetles
1. Don’t feed on carrion, but are carnivorous
A. Often carry mites on their bodies
(1) These mites feed on fly eggs

47. B. Arrival at the corpse before any fly eggs hatch into maggots:
(1) The 1st eggs are eaten and maggot development is delayed
(2) May lead to an incorrect estimate in time of death

49. Other Uses for Insects in Forensic Science
1. Has the body been moved after death?
A. Some insects on the body may be native to the 1st habitat and not the 2nd

50. (1) Will show that the body has been moved following death
  (2) Give an indication of the type of area where the murder actually took place

51. 2. Has the body been disturbed after death?
A. Did the killer return to the scene of the crime
(1) This may disturb the insects cycle

52. (a) The entomologist may be able to determine the date of death
  (b) The entomologist may be able to date the return of the killer

53. 3. Presence and position of wounds:
A. Decomposition may obscure wounds

54. B. Insects colonize remains in a. specific pattern – Usually laying
B. Insects colonize remains in a specific pattern – Usually laying eggs first in the facial orifices, unless there are wounds, in
which case they will colonize these first, then proceed down the body

55. (1). Maggot activity that is cen-. tered away from the natural
(1) Maggot activity that is cen- tered away from the natural orifices – This is likely the site of a wound
  (2) Maggot activity on the palm of the hands or on the arms – Defensive wounds

56. 4. The presence of drugs:
A. There is often not enough flesh left to determine the presence of
drugs

57. (1) Bioaccumulate – The accu-
mulation of substances
(2) Maggots can be analyzed to determine the type of drug present

58. 5. Place a suspect at the scene of a crime:
A. Insects found on a certain type of vegetation can connect a suspect to a specific location

59. 6. Child or Senior Abuse / Neglect:
A. Cutaneous Myiasis – Insect colony on wounds/unclean areas
on a living person

60. (1) Victim is still alive, but maggot infested
(2) Entomologist will be able to tell when the wound or abuse
occurred

61. Limitations of Forensic Entomology:
1. Temperature
2. Seasonal – Insects are only com- monly used in spring, summer, and fall

62. A. Victim found in the spring with. little to no insect presence – May
A. Victim found in the spring with little to no insect presence – May have died during the winter

63. 3. Body Disposal – Can exclude insects
A. Freezing the body
B. Burial – If a body is buried deeply would exclude most insects

64. C. Wrapped – A victim that is. tightly wrapped would delay
C. Wrapped – A victim that is tightly wrapped would delay insect infestation

65. 4. Drugs – May affect the develop-
ment of the insects

66. Life History of Flies
Table 1: The development of body length (in mm) of some fly species during their metamorphosis at 72oF
(L = Larvae; P = Pupae; A = Adult Fly).

67. Days after Death
House
Fly
Blow
Flesh
Skipper Fly 1
Egg
L 9 – 11 2
L 12 – 16 3
L 17 – 20 4
L 6
L 21 – 25 5
L 26 – 30

68. D.A.D.
House
Blow
Flesh
Skipper 11
L 31 – 35
L 26 – 30
P 38 – 40
L 10 – 13 12
P 26 – 29
L 14 – 16 13
P 13 – 15 14
P 31 – 34 15 16 17 18
A 30 – 32

69. * Pupae Species cannot be determined except
by the size of the Pupae

70. Temp.
House Fly
Blow Fly
50-54
Delay 5 days
55-65
Delay 4 days
55-60
66-69
Delay 2 days
61-65
Delay 3 days
70-74
Delay 1 day
66-70
75-79
No Effect
71-75
80-81
Accelerate 1 day
76-79
82-84
Accelerate 2 days
80-84
85+
Accelerate 3 days

71. Ecological
Traits
House
Fly
Blow
Flesh
Skipper
Habitat
Urban and Rural
Urban and
Rural
Urban
Lighting
Full to Partial Sun
Partial Sun to Shade
Prefers Sun
Drugs
No Effect
Sensitive to Drugs