The name "Spider" results from the appearance of the pattern of this mutation: the black zones are very reduced and disentangled as a cobweb... According to specimens, the white from the belly recovers a more or less big part of sides.

Some definitions of genetics...

Allele : alleles are the different versions of the same gene
Dominant allele : an allele is said to be dominant if he is able to pass alone a characteristic trait of the parents to the descendants.
Recessive allele : an allele is said to be recessive if he is not able to pass alone a characteristic trait of the parents to the descendants.
Co-dominant allele : alleles are said to be co-dominant when together they are able to pass a characteristic trait to the descendants.
Homozygous : An individual is said to be homozygous for a given gene if he possesses two identical alleles of this gene.
Heterozygous : An individual is said to be heterozygous for a given gene if he carries two different alleles.

Spider gene is dominant.

male	female	descendants
Spider	Spider	100% of the descendants are Spider
Spider	normal	50% of the descendants are Spider 50% of the descendants are normal

Few possible combinations :
Spider x Albinos
Spider x Pastel (Bumble Bee)
Spider x Ghost (Honey Bee)