The woman, a widow, is battling for life at a government hospital here, police said on Saturday.
The accused Palanivel, a vegetable vendor, of Malliyakari in the district was detained by the local people and handed over to police who arrested him and slapped a rape case.
According to police, the woman was living alone at Gopalapuram in Malliakari. Around midnight on Friday, Palanivel, who has two wives and four children, went to the victim's house and asked for water, but she refused.
Suddenly, he forced his way into the house, allegedly raped her and bit her private parts.
Local residents called an ambulance and rushed the woman to Attur Government Hospital from where she was shifted to Mohan Kumaramangalam Medical College Hospital here.
Doctors said the condition of the woman was critical.