Much progress has been made in describing how it is, in a mechanistic sense
, that some vertebrate hosts (species or individuals) are bitten more than
others, principally because of their odour or appearance. Little attention
has been paid to why, in an evolutionary sense, these particular animals ar
e bitten. Irrespective of the proximate mechanisms of host choice, there mu
st be an intense selection pressure on insects to feed on those hosts that
are most amenable to being bitten. We should be better able to predict host
choice by understanding the evolutionary processes at work.