OUTFLOWS:
ADULTS_DYING ¼ ADULTS*(1 À MASF)/DT
EGGS(t) ¼ EGGS(t À dt) + (BIRTHING À EGGS_DYING À HATCHING) * dt
INIT EGGS ¼ 50
INFLOWS:
BIRTHING ¼ EGG_LAY_RATE*ADULTS
OUTFLOWS:
EGGS_DYING ¼ EGGS*(1 À MSF)/DT
DOCUMENT: Instantaneous survival fraction + instantaneous mortality fraction ¼ 1.
HATCHING ¼ EGGS/T*MSF
EASF ¼ .8 {Experimental daily adult survival fraction per stage, dimensionless.}
EGG_LAY_RATE ¼ 0.5
DOCUMENT: Experimental laying rate. EGGS PER ADULT PER DAY.
ESF ¼ .7 {Experimental egg survival fraction, dimensionless, per stage. Stage ¼
1/EXP MATURE RATE, i.e., 70 eggs per 100 eggs survive each 1/EXP
MATURE RATE days, as noted in the experiment.}
MASF ¼ EXP(LN(EASF)*DT/TA)
MSF ¼ EXP(LN(ESF)/T*DT)
T ¼ 5
DOCUMENT: Inverse is the Experimental Maturation Rate, 1/DAY.
TA ¼ 1
DOCUMENT: One day ¼ experimental period for which adult mortality is
measured.
26.3 Two-Stage Insect Model with a Degree-Day
Calculation Controlling the Maturation Rate
Let us take the model of the previous section and specify the maturation rate as a
function of the temperature. In this model, time and temperature are now the two
independent variables. We have assumed a sine function for the mean daily
temperature and assumed Æ10
F + the mean daily to get the high and low temperature for the day:
DAILY MEAN TEMP ¼ 47 þ 27 Ã SIN 2 Ã PI=365 Ã TIME
ð
Þ
ð 26:7Þ
If the high temperature is less than the threshold or base temperature, no degreedays for that day are calculated. If the minimum temperature for that day is less than
the threshold temperature but the maximum temperature is greater than the threshold, the degree-days, DD 1, are calculated as the maximum temperature minus the
threshold temperature, divided by 2:
26.3 Two-Stage Insect Model with a Degree-Day Calculation Controlling. . .
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