So, if a mojave-lesser BEL bred to a normal produces all mojos and lessers--no normals, no BELs--then it would appear that the two mutations (mojo, lesser) are on the same chromosome, but not necessarily the same gene, although it's a possibility. Pastel and spider mutations are on different chromosomes, and that's why breeding a bumblebee to a normal gets you BBs, spiders, pastels, and normals.

As for the lesser-butter BELs, this single chromosome idea could also be true (different genes for color/pattern mutated on the same chromosome), or the mutation could be in the same gene--either a different mutation of the same gene, or in a different location on the same gene. Breeding this BEL to a normal would also produce only lessers and butters.

Another musing--If these two mutations are in different genes on the same chromosome, then it is possible that they're each working in tandem with another mutation that when homozygous causes leucism. It is not necessarily due to the same lesser or butter gene mutation, but we don't know that yet. So, it is possible that lessers and butters have separate color/pattern mutations, but also have another chromosomally linked gene that wipes out all pigmentation when homozygous.

I really enjoy having this "roundtable" discussion. All of you bring so much insight and get my brains a-thinkin'. I appreciate that.

IMO--I would not smudge the lesser/butter lines. I really like lessers, and when I see one for sale that looks like a butter, I get suspicious.