There is actually a Pokedex attribute organizing system that includes in one of its categories Pokemon with an insectoid body style.
The non-Bug types listed under this are:
-Krabby
-Kingler
-Kabuto
-Corsola
-Lotad
-Trapinch
-Corphish
-Crawdaunt
-Shellos
-Gastrodon
-Drapion
-Cressalia
I also think Vibrava and Flygon look a lot like insects.
Granted, I don't see it in Corsola and Cressalia (maybe it's because Cressalia kinda has a butterfly look going for it?) Lotad doesn't look the part, but further research shows it to be likely based off an insect. Krabby, Kingler, Corphish, and Crawdaunt look like crabs/lobsters of course, but I guess you can say crabs and lobsters are pretty similar looking to insects.