Name ________________________
Block ______
Forensic Entomology ADH
Accumulated Degree Hours (ADH)
The measurement of the thermal input required for the growth and development of insects is
referred to as ADD or ADH. The development of important insects has been studied in the lab
and we and a very good idea of what their life looks like at specific temperatures. However,
temperature does not stay constant, so calculating ADH is not always straight forward. However,
an approximation can be made using daily high and low temperatures. For instance, you would
first have to calculate the mean temperature and then convert to Celsius.
Date
High Temp (F)
Low Temp (F)
5-28-09
5-29-09
5-30-09
77
78
75
51
53
64
Mean Temp (F)
Mean Temp (C)
We next need to consider that each species has a threshold temperature beneath which no
development will occur. For this activity, assume that the threshold is 6 C. Therefore, no
development will occur between 0 and 6 C. You will need to subtract that from the mean temps
for each day (Put in Degree Day column).
Date
High Temp (F)
Low Temp (F)
5-28-09
5-29-09
5-30-09
77
78
75
51
53
64
Mean Temp (C)
Degree Day (C)
Finally, we can do the ACCUMULATED part of the Accumulated Degree Day (ADD).
Date
High Temp (F)
Low Temp (F)
5-28-09
5-29-09
5-30-09
77
78
75
51
53
64
Mean Temp (F)
Mean Temp
(C)
ADD
How is this technique useful? Consider the following scenario:
The body of a homeless man was found near Boulder Creek, Co on April 26 th. There was
damage to the skull which may have resulted from hitting his head on a rock or having been hit
in the head with a rock. It appeared that his body had been there for several days. A CU
(University of CO) entomologist was called to the scene. He identified several larvae from the
man’s skull as being secondary screw worm larvae in the 2nd instar. No pupa were found.
Using the developmental data for the secondary screw worm fly shown below:
Table 1: ADH for Secondary Screw Worm Fly
1st Instar
2nd Instar
3rd Instar
Pupa
Adult
15.6 +/- 2°C (hours to
reach stage)
21.1 +/- 2°C (hours to
reach stage)
26.7 +/- 2°C (hours to
reach stage)
32
70
122
276
588
12
30
72
172
297
18
32
56
112
177
Note how there are 3 different temperatures given. Which one do you use? To determine this,
you will need to calculate the average Degree Hour like you did before. Use columns 1-3 below
to do this. Then calculate ADH.
Table 2: Results
Date
Mean Temp (C)
Degree Hour
4-26-09
4-25-09
4-24-09
4-23-09
4-22-09
4-21-09
4-20-09
4-19-09
4-18-09
23.5
20.5
24
23
23.5
22
22.5
24
23
Ave =
Ave=
ADH
Now match up you average Degree Hour with one of the temperatures given to you in Table 1.
Did you find the correct temp to use in your next calculations? The entomologist found the
larvae on the man’s body to be in the 2nd Instar stage. What are the degree hours that
correspond to this fly being in that stage? It will be a range.
______________________ Degree Hours
Count back to when those eggs might have been laid. What is the earliest those eggs could
have been laid (i.e. what date)? _____________________
What is the maximum date those eggs could have been laid? _________________