Therearen't any. Bug doesn't need one because it has approximately six billion pokemon obtainable before the first gym anyway. Dragon has Swablu and Noibat, though that seems like a rough time through Julia so it's possible you can get a third through the monodragon password, I've never tried it myself so I don't really know. Monorock enables an early Aron and Dwebble, though neither of these are obtained as your starter pokemon.
Swablu is available from headbutt trees, I believe the ones in Seacrest's garden, as of e19.
The only way I can see a dragon starter working is if monodragon guaranteed the police egg to be Trapinch and replaced the Espurr/Munna with Axew, like how ice/rock do with Swinub/Aron. Trading over a lv5 Axew and hoping for Trapinch from the egg was how I was planning to do my dragon mono, at least, or trading over a Trapinch egg if the police egg ended up Axew. (I plan to run every monotype at least once. This is going to take many, many months given the length of postgame lol)
Bug has Kricketot available without battling any trainers with careful movements. Not to mention you can just go throw balls at Spinarak outside the Grand Hall at night before even moving out of Opal Ward. (Or Combee/Pineco with easyhms password for headbutt trees in the same spot.) Not to mention there are no real starter-equal bug types that wouldn't already be available very early besides Venipede, which would be pretty oppressive early on for similar reasons to Torchic. (Speed Boost + Iron Defense as Whirlipede's evolve move + Baton Pass as Scolipede's evolve move means he has insane utility even without access to SD and Poison Jab + Earthquake until late)
But yeah, they replaced Drilbur in the police egg with Trapinch (and Phantump with Litwick) so trading an egg over is just a backup plan in case the monodragon password opts for the 50/50 in favor of Axew rather than the antlion. Honestly the change is fair, Excadrill has always been extremely good and even lack of good steel STAB until post city restore doesn't really hold it back when it gets SD/EQ by level up...
Yeah, I'd have both at that point lol. Axew replacing my starter and Trapinch from the police egg. (The "trade over a Trapinch egg" was in reference to if I got Axew again from the egg-- I'd trade over a Trapinch to replace the police egg.) No worries. :) There are 2 ways I can see potentially handling Serra: Break the field with EQ or Seed + Smash Turtonator and pray lol. We'll have to see when we get there, I'm kinda a trial-by-fire player when testing strategies lol
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