Wormwood: you can always "squeegee" the dirt out of the night crawlers - that's how you prep them for human consumption !! Seriously, you squeeze the dirt out the worms and then cook as desired. The best strategy is to dry them, pound to powder and add to stews/broths, then you can't really taste them!!! Yum, yum! (According to my SAS (Secret Air Service) wilderness survival skill book)...

Lilypad: I agree - I always tell people the "space between the eyes rule" if they are new to the hobby... If in doubt, go with smaller feeders. Frank Indiviglio, an expert in the field, attributes his success with American toads to [in part] feeding them appropriately sized (i.e. smaller) food items...

Poly: Over the ~35 years I have been catching wild amphibians, I have noticed that there are often pronounced geographical differences in size, coloration, etc. I remember reading a report of a population of American toads with females reaching 6+ inches in length. This is much larger than typical for American toads! I'll see if I can find the report. There are also the occasional atypical individuals in any population...