Under the noted conditions the 10% healthy and an additional fraction of the
healthy adults based empirically on the total number of adults also migrate. Note
well the order of the nested IF statement; the first one is checked first and if the
condition holds the first statement is executed and the program goes no further.
Otherwise all the adults flee. This same statement is also true of the adults in the
other field.}
OUTFLOWS:
DYING_2_TO_1 ¼ .25 * LEAVE_1_TO_2 {Individuals per Time Period}
ARRIVING_1_TO_2 ¼ .75 * LEAVE_1_TO_2 {Individuals per Time Period}
LEAVE_2_TO_1(t) ¼ LEAVE_2_TO_1(t À dt) + (IMMIG_2_TO_1 À DYING_
2TO1 À ARRIVING_2_TO_1) * dt
INIT LEAVE_2_TO_1 ¼ 0
INFLOWS:
IMMIG_2_TO_1 ¼ IF ADULTS_H2 À (.1 * ADULTS_H2 + .9 * FRXNL_CAP2)
> 0 THEN (.1 * ADULTS_H2 + .9 * FRXNL_CAP2) ELSE IF ADULTS_H2 > 0
THEN ADULTS_H2 ELSE 0 {Individuals per Time Period}
OUTFLOWS:
DYING_2TO1 ¼ .25 * LEAVE_2_TO_1 {Individuals per Time Period}
ARRIVING_2_TO_1 ¼ .75 * LEAVE_2_TO_1 {Individuals per Time Period}
NYMPHS_D1(t) ¼ NYMPHS_D1(t À dt) + (BIRTHS_D1 À DYING_DN1 À
MATURING_D1) * dt
INIT NYMPHS_D1 ¼ 0 {Initial diseased eggs}
INFLOWS:
BIRTHS_D1 ¼ IF (K1-ALL_ADULTS_1) > 0 THEN BR_D * ADULTS_D1
ELSE 0 {Individuals per Time Period}
OUTFLOWS:
DYING_DN1 ¼ (1 À MNSF_D) * NYMPHS_D1/DT {Individuals per Time
Period}
MATURING_D1 ¼ MNSF_D * NYMPHS_D1/TN1_D {Individuals per Time
Period}
NYMPHS_D2(t) ¼ NYMPHS_D2(t À dt) + (BIRTHS_D2 À DYING_DN2 À
MATURING_D2) * dt
INIT NYMPHS_D2 ¼ 0 {Initial diseased eggs}
INFLOWS:
BIRTHS_D2 ¼ IF (K2-ALL_ADULTS_2) > 0 THEN BR_D * ADULTS_D2
ELSE 0 {Individuals per Time Period}
OUTFLOWS:
DYING_DN2 ¼ (1 À MNSF_D) * NYMPHS_D2/DT {Individuals per Time Period}
MATURING_D2 ¼ MNSF_D * NYMPHS_D2/TN1_D {Individuals per Time
Period}
NYMPHS_H1(t) ¼ NYMPHS_H1(t À dt) + (BIRTHING_H1 À DYING_HN1 À
MATURE_H1 À INFECTION_1) * dt
INIT NYMPHS_H1 ¼ 0 {Initial Healthy eggs}
33.2 Immigrating Insects Model Equations
279