Auto insurer Progressive July net drops 31 percent

(Adds financial details)

NEW YORK, Aug 13 (Reuters) - Progressive Corp , the No. 3 U.S. auto insurer, said on Wednesday that monthly earnings fell 31 percent as it lost money on investments.

Net income in July dropped to $81.8 million, or 12 cents a share, from $118.5 million, or 16 cents a share, a year earlier.

The company recorded pretax net realized losses of $16.1 million on investments in July, compared with a year-earlier gain of $13.2 million.

Net premiums written were flat at $1.38 billion, while net premiums earned were 2 percent lower at $1.31 billion. (Reporting by Lilla Zuill; Editing by Lisa Von Ahn)