Genome studies of insects and plant for finding their relationship may solve some of the pest control problems and prevent them from damaging crops. Differences in genes (alleles) within the genome of insect pest population may produce variations in characters by appearing resistant genotypes. Molecular biology by sequencing DNA has discovered genotype variation within species of insect pest population. Stress can cause whole genome changes with different effects for insect crop relationship. Genome methylation and their natural control of heterochromatin, by action on chromosome and gene expression, may produce genotype adaption for increasing crop damage. This article intends to describe outlines of insect pest traits by studying their genome. An example of genomic studies used to discover ecology of an important cow pea pest in a few West African countries is described. The possibility of gene expression helping insect pests to adapt to crop and its environment is discussed.