The spider morph is heterozygous for the spider gene, so each of its offspring have a 50/50 chance of getting the spider version of the gene from the spider parent.

Same for the het pied side and the het pied parent, 50% chance of giving the pied gene to each offspring.

The main difference between the pied and the spider sides of the equation is that as some sort of dominant type mutation you can visually identify the het spiders. There is some controversy as to if you can sometimes identify the het piebalds too. It's considered a recessive mutation so you aren't supposed to be able to but there is evidence that some piebald might have co-dominant leanings.

The chance of an egg hitting on both the 50% chance of getting the spider mutant version and the 50% chance of getting the piebald mutant version is 25%. However, once the eggs hatch and you have picked out the ones that you know hit the spider gene they have a 50% chance of also being het piebald. In a sense you have cheated the odds because you don't have to guess on the spider side of the equation, you can see the hets. Might you be able to cheat the odds further looking for signs of which spiders might be het pied?

I just picked out my first morph last night. A male spider from a breeding loan of one of my possible possible het pied females to a spider male. My female had a little of the markings that might indicate a better chance of her being a het pied than her text book 25% chance (the daughter of a 50% chance het pied). However, they weren’t very good markings and it's been proven that normals can have them too and that some het pieds don't have them. Still I picked the lightest most reduced pattern male spider with the hope that if the pied gene was present in the clutch it might manifest its self in a spider that way given that the pied spiders have the white up from the belly everywhere but the head. Technically my spider is only a 12.5% chance het piebald so a long shot to be sure as three generations removed from for sure having the piebald gene. I'm still planning on trying him on one of my better marked 25% chance het pied girls when they get up to size. Perhaps I’ll be able to determine if his mom is het pied by then and upgrade his status to 50% chance het pied.

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