The reason that Jerry lies about having a mother is not directly stated in Marjorie Rawlings's short story "A Mother in Mannville." Readers must make inferences as to the reason. Here are some things to think about to help in making inferences:
1. Jerry is twelve years old and living in an orphanage. He develops a friendship of sorts with the narrator, who is renting a cabin near the orphanage in order to do some writing. Jerry falls in love with the narrator's dog and spends time with him while the narrator is away.
2. Jerry is often invited into the cabin as it gets colder. The narrator describes the chats she has with him, as well as the times he and her pointer dog Pat doze in front of the fire together while she writes. This must have felt like the closest thing to a family he'd ever known.
3. When people have challenging circumstances in their lives, they often escape into imaginary realities in order to cope with their present difficulties.