Chapter 33
Diseased and Healthy Immigrating Insects
And migrant tribes these fruitful shorelands hail.
(Joel Barlow, 1807, The Columbiad, ii. 178)
33.1 Immigrating Insects Model
This chapter builds on the models developed in Chap. 26 by distinguishing two cohorts
of a population infected with a disease. The two populations modeled here are insects
that suffer from a disease that increases mortality for the infected nymphs and adults
and also decreases their egg-laying rate. Unlike the previous chapters we assume here
two populations of insects, living in two fields. One of the fields has generally better
living conditions than the other, although the current year’s carrying capacities are
randomly generated and there is some overlap in the ranges within which the carrying
capacity fluctuates. Carrying capacity has a direct effect on birth rates.
The carrying capacities of the two fields are defined as
K1 ¼ IF CARRY R1 > :666 THEN 2
ELSE IF CARRY R1 < :333 THEN :5
ELSE 1
ð33:1Þ
and
K2 ¼ IF CARRY R2 > :666 THEN 4
ELSE IF CARRY R2 < :333 THEN 1
ELSE 2
ð33:2Þ
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_33,
© Springer International Publishing Switzerland 2014
273
Diseased and Healthy Immigrating Insects
And migrant tribes these fruitful shorelands hail.
(Joel Barlow, 1807, The Columbiad, ii. 178)
33.1 Immigrating Insects Model
This chapter builds on the models developed in Chap. 26 by distinguishing two cohorts
of a population infected with a disease. The two populations modeled here are insects
that suffer from a disease that increases mortality for the infected nymphs and adults
and also decreases their egg-laying rate. Unlike the previous chapters we assume here
two populations of insects, living in two fields. One of the fields has generally better
living conditions than the other, although the current year’s carrying capacities are
randomly generated and there is some overlap in the ranges within which the carrying
capacity fluctuates. Carrying capacity has a direct effect on birth rates.
The carrying capacities of the two fields are defined as
K1 ¼ IF CARRY R1 > :666 THEN 2
ELSE IF CARRY R1 < :333 THEN :5
ELSE 1
ð33:1Þ
and
K2 ¼ IF CARRY R2 > :666 THEN 4
ELSE IF CARRY R2 < :333 THEN 1
ELSE 2
ð33:2Þ
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_33,
© Springer International Publishing Switzerland 2014
273