The Ppss would be a bee with homozygous spider traits so when you do a square im pretty sure it would be Ps ps Ps ps because all genes that are s would show the trait.
for the square you just did the way i used to do it would just be
----S N
P | PS - PN
N | SN - NN
hopefully that works out when i submit but i can still tell that its 25% normal 25% bumblebee 25% spider and 25% pastel. I think it just gets harder once you start doing bumblebeexbumbleebee so you might not be able to do it the way i used to