Fig 9. The trajectory of the system Eq (7) with initial condition (0,0,0,0,10000,0) and parameters L = 1500, w = 21000, v = 10000, α ₄ = 0.001, α ₃ = 0.0005, α ₂ = 1, α ₁ = 0.001, φ ₁ = 1/3, φ ₂ = 1, σ = 0.001, β ₁ = 1/5, β ₂ = 1/13, and μ = 1/30.

This figure illustrates what will happen to the colony if the value of α ₄ (the rate at which adult bees become infected upon contact with the foraging area) is non-zero.