  Based on a Fermi liquid picture, the temperature effect on the
impurity-induced spatial modulation of local density of states (LDOS) is
investigated for the d-wave superconductor Bi$_2$Sr$_2$CaCu$_2$O$_8$, in the
context of scanning tunneling microscopy (STM). It is found that stripe-like
structure exists even in the normal state due to a local-nesting mechanism,
which is different from the octet scattering mechanism proposed by McElroy $et
al$. {[Nature {\bf 422}, 592 (2003)]} in the d-wave superconducting ($d$SC)
state. The normal-state spectra, when Fourier-transformed into the reciprocal
space, can reveal the information of the entire Fermi surface at a single
measuring bias, in contrast to the point-wise tracing proposed by McElroy $et
al$. This may serve as another way to check the reality of Landau
quasiparticles in the normal state. We have also re-visited the spectra in the
$d$SC state and pointed out that, due to the Umklapp symmetry of the lattice,
there should exist additional peaks in the reciprocal space, but experimentally
yet to be found.
