Offensively, the Bug-type is somewhat flawed. It is effective against Psychic&Dark, which are common, but its strength against Grass-types is reduced by the common Grass/Poison mixture. Since six types resist Bug attacks (making it the second-most ineffective type after Grass), Bug moves still don’t deal a lot of damage. Defensively, it is still not up to par because of its low DEF&the fact that there are many that are also Flying-types, multiplying their weakness to Rock-types. In this way, their resistance to Ground&Fighting-types are of little use, seeing as many of both kinds can learn Rock moves. The Bug/Steel Pokemon prove particularly effective as they only have one (double) weakness against Fire and a total of ten resistances (including an immunity).
Bug Type, by Elaine.