In Black:
Weedle
Obtainable by breeding.
Kakuna
Route 12
Beedrill
Route 12
Murkrow
Abundant Shrine
Houndour
Route 9; May be part of a Outbreak
Houndoom
Obtainable by Evolution.
Shroomish
Route 11; May be part of an Outbreak
Breloom
Obtainable by Evolution
Plusle
Route 6; May be part of an Outbreak
Volbeat
Route 3
Honchkrow
Abundant Shrine
In White:
Caterpie
Obtainable by breeding.
Metapod
Route 12
Butterfree
Route 12
Paras
Route 11; May be part of an Outbreak
Parasect
Obtainable by Evolution.
Misdreavus
Abundant Shrine
Poochyena
Route 9; May be part of an Outbreak
Mightyena
Obtainable by Evolution
Minum
Route 6; May be part of an Outbreak
Illumise
Route 3
Mismagius
Abundant Shrine
Source: http://www.serebii.net/blackwhite/exclusives.shtml
Hope this helped!!!