The Senate is part of Congress but The House doesn't disclose trades. The Stock Act of 2012 prohibits insider trading for the Senate and provides that trades are disclosed, which is why the data is available for that branch.
This is not a factual statement. See the Clerk of the House of Representatives [0].
The main issue is that many of these trades are submitted by scanned, handwritten documents.
[0] http://clerk.house.gov/public_disc/financial-search.aspx