Sammy is trying to figure out how a girl's mind works. When these three girls come into the store improperly dressed, or undressed, he is stunned with joy watching them walk around the store.
His shock leads to a thought, how could anyone make such a rash choice, walking around in such a state of undress in public. In the 1960s there was a standard for young ladies, many of them wore hats and gloves when they were dressed. Most people observed the polite rules of society, so therefore, most girls would not walk around in a store wearing only a bathing suit.
So Sammy, looking at these girls, thinks about the lead girl like a Queen Bee, leading the others. He wonders how her brain works. He is a teenage boy trying to understand what makes a girl tick. A common thought, especially, for Sammy at this moment, who wants desperately to be noticed by these girls.
He is so driven to be noticed that he makes a drastic decision, without thinking of the consequences. He blurts out: "I quit," when the girls are chastised for coming into the store improperly dressed.
"You never know for sure how girls' minds work (do you really think it's a mind in there or just a little buzz like a bee in a glass jar?)" (Updike)
The comparison can be viewed in different ways. First it could be seen as insulting to women, since alluding to a person as an insect is offensive.
On the other hand, bees are valued animals. They are viewed as hard working, busy insects. They have a way of communication that no one has been able to decipher completely yet. This says that Sammy has at least a bit of an idea that women are complex creatures (despite his objectifying of them).
The fact that he compares everybody to animals can be analyzed as as well (birds, sheep, bees, pigs).
Angels--see Dante's Paradise, Canto XXXI.
Try this website for symbolism