  If C=C_\phi denotes the mapping cone of an essential phantom map \phi from
the suspension of the Eilenberg-Mac Lane complex K=K(Z,5) to the 4-sphere S=S^4
we derive the following properties: (1) The LS category of the product of C
with any n-sphere S^n is equal to 3; (2) The LS category of the product of C
with itself is equal to 3, hence is strictly less than twice the LS category of
C. These properties came to light in the course of an unsuccessful attempt to
find, for each positive integer m, an example of a pair of 1-connected
CW-complexes of finite type in the same Mislin (localization) genus with LS
categories m and 2m. If \phi is such that its p-localizations are inessential
for all primes p, then by the main result of [J. Roitberg, The
Lusternik-Schnirelmann category of certain infinite CW-complexes, Topology 39
(2000), 95-101], the pair C_*, C where C_*= S wedge \Sigma ^2 K, provides such
an example in the case m=1.
