Both bees would have to be heterozygous. This meaning that they are still long winged but is a carrier of the trait to have a short wing off spring
Eccentricity is the ratio of the distance from the center of an ellipse to one of its foci to the distance from the center of the ellipse to one of its vertices.
There isn’t exactly a name for it other than “folded sarcolemma”, however, the end of the motor neuron does extend some projections into these spaces.