vannessa sp. rarity

[Yan Boulanger]

Hi!
Since 1993, I saw only  3 specimens of Vanessa cardui (L.) and 2
of the Vanessa virginiensis (Drury) specie even if I was almost always
in the field for
the past 5 summer (except this year).
Species     / Year   1993       1994    1995           1996
1997      1998
Vanessa virginiensis   0          1(24/07)  0
0          0         1(?/09)
Vanessa cardui          0             0        3(25/07,
0           0        0
                                                        mid-august
                                                        and   21/08)

I know that these species are supposed to be common or very common but
they are cyclic.
Also, I heard that a polyedre sickness was presented sometimes on the
caterpillar
of those two species and can kill a great number of caterpillars in a
matter of days.
Is it the case for the past 5 years?
Maybe they have just migrated from our region (Bas-St-Laurent, Qc. Ca.).

I would like to know if is it the same in your region (in america).
Thx, Yan Boulanger