function v = stagepp(t, Y, Z, p,a,b,dj,tau,d,m)
v = zeros(2,1);

x = Y(1);
y = Y(2);
ylag = Z(:,1);

dxdt = x*(1-x)-y*p*x/(1+a*x);
dydt = b*exp(-dj*tau)*ylag(2)*p*ylag(1)/(1+a*ylag(1))-d*y-m*y*y;
v = [dxdt; dydt];

% Predator-prey model with stage structure, 4/18/02