The group listing is:

Bill
Bill Collins is the narrator of the series. He has red hair and freckles, and is 10 years of age in the first book. Bill is one of two members of the gang to have no nickname. His best friend is Poetry, and he is a single child at first, but later has a little sister named Charlotte Ann. His father, (Theodore Collins) is a farmer, but Bill wants to be a doctor when he grows up. He is a very good Christian. Poetry (Leslie Thompson)
Poetry is sometimes called "the barrel-shaped member of the gang" because he is very chubby. He always boasts about his detective abilities, and usually has a tent pitched in his backyard. His nickname is "Poetry", because he has memorized so many poems, he can quote one for most any situation. Dragonfly (Roy Gilbert)
Dragonfly is the skinniest and most allergic member of the gang.
Wilma
Wilma Collins is the narrator of the series. She has red hair and freckles, and is 10 years of age in the first book. Wilma is one of two members of the gang to have no nickname. Her best friend is Poetry, and she is a single child at first, but later has a little sister named Charlotte Ann. Her father, (Theodore Collins) is a farmer, but Wilma wants to be a doctor when she grows up. She is a very good Christian. Poetry (Leslie Thompson)
Poetry is sometimes called "the barrel-shaped member of the gang" because he is very chubby. He always boasts about his detective abilities, and usually has a tent pitched in his backyard. His nickname is "Poetry", because he has memorized so many poems, he can quote one for most any situation. Dragonfly (Roy Gilbert)
Dragonfly is the skinniest and most allergic member of the gang.