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Date Permissions Signed


Date of Award

Winter 2019

Document Type

Masters Thesis

Department or Program Affiliation


Degree Name

Master of Arts (MA)



First Advisor

Koetje, Todd A.

Second Advisor

Campbell, Sarah K.

Third Advisor

Young, Kathleen Z.


Accurately estimating the time since a decedent was alive (postmortem interval/PMI) after the first 24 to 72 hours is dependent upon the ability of forensic entomologists to predict the colonization of remains by insects. Estimations of PMI must be modified for local conditions. This study examines the abiotic environmental factors (ambient temperature, relative humidity, light intensity, rainfall, barometric pressure, and wind speed) that influence the appearance of a specific subset of colonizing insects of forensic importance and known to show up first in other North American settings. These insects include blow and bottle flies, from the taxonomic family of Calliphoridae. The goal is to clarify the impact of abiotic environmental factors on predicting the probability of colonization by blow flies in Eastern Washington to more accurately estimate the postmortem interval (PMI). The hypothesis is that ambient temperature, light intensity, and relative humidity will be the most significant factors. About 1/3 to 1/2 of a pound of liver was placed in bowls protected by plastic cages at three locations that differ in terms of the type of vegetation. Logistic regression utilizing SPSS 25.0 (2017) generated equations of probability for blow fly colonization based on the significant abiotic environmental variables. Results show that ambient temperature, relative humidity, and light intensity are all significant predictor variables in blow fly colonization. In addition to studies establishing equations for the probability of blow fly colonization in other geographic regions, further studies are needed on the effects of wildfire smoke on blow fly colonization and activity.




postmortem interval, PMI, oviposition, logistic regression, liver, Calliphoridae


Western Washington University

OCLC Number


Subject – LCSH

Forensic entomology--Washington (State), Eastern; Blowflies--colonization--Washington (State), Eastern; Postmortem changes

Geographic Coverage

Washington (State), Eastern




masters theses




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